ulisp-avr-nano.ino

/* uLisp AVR-Nano Release 4.6 - www.ulisp.com
   David Johnson-Davies - www.technoblogy.com - 13th June 2024
   
   Licensed under the MIT license: https://opensource.org/licenses/MIT
*/

// Lisp Library
const char LispLibrary[] PROGMEM = "";

// Compile options

#define checkoverflow
// #define resetautorun
#define printfreespace
// #define printgcs
// #define sdcardsupport
// #define lisplibrary
#define assemblerlist
// #define lineeditor
// #define vt100

// Includes

// #include "LispLibrary.h"
#include <avr/sleep.h>
#include <setjmp.h>
#include <SPI.h>
#include <limits.h>
#include <EEPROM.h>

#if defined(sdcardsupport)
#include <SD.h>
#define SDSIZE 172
#else
#define SDSIZE 0
#endif

// Platform specific settings

#define WORDALIGNED __attribute__((aligned (2)))
#define OBJECTALIGNED __attribute__((aligned (4)))
#define BUFFERSIZE 22                     /* longest builtin name + 1 */

#if defined(ARDUINO_AVR_UNO)
  #define WORKSPACESIZE (320-SDSIZE)      /* Objects (4*bytes) */
  #define EEPROMSIZE 1024                 /* Bytes */
  #define STACKDIFF 1
  #define CPU_ATmega328P

#elif defined(ARDUINO_AVR_MEGA2560)
  #define WORKSPACESIZE (1344-SDSIZE)     /* Objects (4*bytes) */
  #define EEPROMSIZE 4096                 /* Bytes */
  #define STACKDIFF 320
  #define CPU_ATmega2560

#elif defined(__AVR_ATmega1284P__)
  #include "optiboot.h"
  #define WORKSPACESIZE (2944-SDSIZE)     /* Objects (4*bytes) */
//  #define EEPROMSIZE 4096                 /* Bytes */
  #define FLASHWRITESIZE 16384            /* Bytes */
  #define CODESIZE 96                     /* Bytes <= 256 */
  #define STACKDIFF 320
  #define CPU_ATmega1284P

#elif defined(ARDUINO_AVR_NANO_EVERY)
  #define WORKSPACESIZE (1060-SDSIZE)     /* Objects (4*bytes) */
  #define EEPROMSIZE 256                  /* Bytes */
  #define STACKDIFF 160
  #define CPU_ATmega4809
  
#elif defined(ARDUINO_AVR_ATmega4809)     /* Curiosity Nano using MegaCoreX */
  #define Serial Serial3
  #define WORKSPACESIZE (1065-SDSIZE)     /* Objects (4*bytes) */
  #define EEPROMSIZE 256                  /* Bytes */
  #define STACKDIFF 320
  #define CPU_ATmega4809

#elif defined(ARDUINO_AVR_ATtiny3227)
  #define WORKSPACESIZE (514-SDSIZE)      /* Objects (4*bytes) */
//  #define EEPROMSIZE 256                  /* Bytes */
  #define STACKDIFF 1
  #define CPU_ATtiny3227

#elif defined(__AVR_AVR128DA48__)
  #include <Flash.h>
  #define Serial Serial1
  #define WORKSPACESIZE (2920-SDSIZE)     /* Objects (4*bytes) */
  #define FLASHWRITESIZE 16384            /* Bytes */
  #define CODESIZE 96                     /* Bytes <= 512 */
  #define STACKDIFF 320
  #define CPU_AVR128DX48
  #define LED_BUILTIN 20

#elif defined(__AVR_AVR128DB48__)
  #include <Flash.h>
  #define Serial Serial3
  #define WORKSPACESIZE (2920-SDSIZE)     /* Objects (4*bytes) */
  #define FLASHWRITESIZE 16384            /* Bytes */
  #define CODESIZE 96                     /* Bytes <= 512 */
  #define STACKDIFF 320
  #define CPU_AVR128DX48
  #define LED_BUILTIN 20
  
#else
#error "Board not supported!"
#endif

// C Macros

#define nil                NULL
#define car(x)             (((object *) (x))->car)
#define cdr(x)             (((object *) (x))->cdr)

#define first(x)           car(x)
#define rest(x)            cdr(x)
#define second(x)          first(rest(x))
#define cddr(x)            cdr(cdr(x))
#define third(x)           first(cddr(x))

#define push(x, y)         ((y) = cons((x),(y)))
#define pop(y)             ((y) = cdr(y))

#define protect(y)         push((y), GCStack)
#define unprotect()        pop(GCStack)

#define integerp(x)        ((x) != NULL && (x)->type == NUMBER)
#define symbolp(x)         ((x) != NULL && (x)->type == SYMBOL)
#define stringp(x)         ((x) != NULL && (x)->type == STRING)
#define characterp(x)      ((x) != NULL && (x)->type == CHARACTER)
#define streamp(x)         ((x) != NULL && (x)->type == STREAM)

#define mark(x)            (car(x) = (object *)(((uintptr_t)(car(x))) | MARKBIT))
#define unmark(x)          (car(x) = (object *)(((uintptr_t)(car(x))) & ~MARKBIT))
#define marked(x)          ((((uintptr_t)(car(x))) & MARKBIT) != 0)
#define MARKBIT            1

#define setflag(x)         (Flags |= 1<<(x))
#define clrflag(x)         (Flags &= ~(1<<(x)))
#define tstflag(x)         (Flags & 1<<(x))

#define issp(x)            (x == ' ' || x == '\n' || x == '\r' || x == '\t')
#define isbr(x)            (x == ')' || x == '(' || x == '"' || x == '#')
#define longsymbolp(x)     (((x)->name & 0x03) == 0)
#define longnamep(x)       (((x) & 0x03) == 0)
#define arraysize(x)       (sizeof(x) / sizeof(x[0]))
#define stringifyX(x)      #x
#define stringify(x)       stringifyX(x)
#define PACKEDS            17600
#define BUILTINS           64000
#define ENDFUNCTIONS       1536

#define SDCARD_SS_PIN 10

#if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
#define PROGMEM
#define PSTR(s) (s)
#endif

// Constants

const int TRACEMAX = 3; // Number of traced functions
enum type { ZZERO=0, SYMBOL=2, CODE=4, NUMBER=6, STREAM=8, CHARACTER=10, STRING=12, PAIR=14 };  // STRING and PAIR must be last
enum token { UNUSED, BRA, KET, QUO, DOT };
enum stream { SERIALSTREAM, I2CSTREAM, SPISTREAM, SDSTREAM, STRINGSTREAM };
enum fntypes_t { OTHER_FORMS, TAIL_FORMS, FUNCTIONS, SPECIAL_FORMS };

// Stream names used by printobject
const char serialstream[] PROGMEM = "serial";
const char i2cstream[] PROGMEM = "i2c";
const char spistream[] PROGMEM = "spi";
const char sdstream[] PROGMEM = "sd";
const char stringstream[] PROGMEM = "string";
PGM_P const streamname[] PROGMEM = {serialstream, i2cstream, spistream, sdstream, stringstream};

// Typedefs

typedef uint16_t symbol_t;
typedef uint16_t builtin_t;
typedef uint16_t chars_t;

typedef struct sobject {
  union {
    struct {
      sobject *car;
      sobject *cdr;
    };
    struct {
      unsigned int type;
      union {
        symbol_t name;
        int integer;
        chars_t chars; // For strings
      };
    };
  };
} object;

typedef object *(*fn_ptr_type)(object *, object *);
typedef void (*mapfun_t)(object *, object **);
typedef int (*intfn_ptr_type)(int w, int x, int y, int z);

typedef const struct {
  const char *string;
  fn_ptr_type fptr;
  uint8_t minmax;
} tbl_entry_t;

typedef int (*gfun_t)();
typedef void (*pfun_t)(char);

enum builtins: builtin_t { NIL, TEE, NOTHING, OPTIONAL, AMPREST, LAMBDA, LET, LETSTAR, CLOSURE, QUOTE, DEFUN, DEFVAR, EQ,
CAR, FIRST, CDR, REST, NTH, CHAR, STRINGFN, PINMODE, DIGITALWRITE, ANALOGREAD, ANALOGREFERENCE, REGISTER,
FORMAT, 
 };

// Global variables

uint8_t FLAG __attribute__ ((section (".noinit")));

object Workspace[WORKSPACESIZE] OBJECTALIGNED;

jmp_buf exception;
unsigned int Freespace = 0;
object *Freelist;
unsigned int I2Ccount;
unsigned int TraceFn[TRACEMAX];
unsigned int TraceDepth[TRACEMAX];
builtin_t Context;

object *GlobalEnv;
object *GCStack = NULL;
object *GlobalString;
object *GlobalStringTail;
int GlobalStringIndex = 0;
uint8_t PrintCount = 0;
uint8_t BreakLevel = 0;
char LastChar = 0;
char LastPrint = 0;
uint16_t RandomSeed;

// Flags
enum flag { PRINTREADABLY, RETURNFLAG, ESCAPE, EXITEDITOR, LIBRARYLOADED, NOESC, NOECHO };
volatile uint8_t Flags = 0b00001; // PRINTREADABLY set by default

// Forward references
object *tee;
void pfstring (PGM_P s, pfun_t pfun);

inline symbol_t twist (builtin_t x) {
  return (x<<2) | ((x & 0xC000)>>14);
}

inline builtin_t untwist (symbol_t x) {
  return (x>>2 & 0x3FFF) | ((x & 0x03)<<14);
}

// Error handling

void errorsub (symbol_t fname, PGM_P string) {
  pfl(pserial); pfstring(PSTR("Error: "), pserial);
  if (fname != sym(NIL)) {
    pserial('\'');
    psymbol(fname, pserial);
    pserial('\''); pserial(' ');
  }
  pfstring(string, pserial);
}

void errorend () { pln(pserial); GCStack = NULL; longjmp(exception, 1); }

void errorsym (symbol_t fname, PGM_P string, object *symbol) {
  errorsub(fname, string);
  pserial(':'); pserial(' ');
  printobject(symbol, pserial);
  errorend();
}

void errorsym2 (symbol_t fname, PGM_P string) {
  errorsub(fname, string);
  errorend();
}

void error (PGM_P string, object *symbol) {
  errorsym(sym(Context), string, symbol);
}

void error2 (PGM_P string) {
  errorsym2(sym(Context), string);
}

void formaterr (object *formatstr, PGM_P string, uint8_t p) {
  pln(pserial); indent(4, ' ', pserial); printstring(formatstr, pserial); pln(pserial);
  indent(p+5, ' ', pserial); pserial('^');
  error2(string);
  pln(pserial);
  GCStack = NULL;
  longjmp(exception, 1);
}

// Save space as these are used multiple times
const char notanumber[] PROGMEM = "argument is not a number";
const char notaninteger[] PROGMEM = "argument is not an integer";
const char notastring[] PROGMEM = "argument is not a string";
const char notalist[] PROGMEM = "argument is not a list";
const char notasymbol[] PROGMEM = "argument is not a symbol";
const char notproper[] PROGMEM = "argument is not a proper list";
const char toomanyargs[] PROGMEM = "too many arguments";
const char toofewargs[] PROGMEM = "too few arguments";
const char noargument[] PROGMEM = "missing argument";
const char nostream[] PROGMEM = "missing stream argument";
const char overflow[] PROGMEM = "arithmetic overflow";
const char divisionbyzero[] PROGMEM = "division by zero";
const char indexnegative[] PROGMEM = "index can't be negative";
const char invalidarg[] PROGMEM = "invalid argument";
const char invalidkey[] PROGMEM = "invalid keyword";
const char illegalclause[] PROGMEM = "illegal clause";
const char invalidpin[] PROGMEM = "invalid pin";
const char oddargs[] PROGMEM = "odd number of arguments";
const char indexrange[] PROGMEM = "index out of range";
const char canttakecar[] PROGMEM = "can't take car";
const char canttakecdr[] PROGMEM = "can't take cdr";
const char unknownstreamtype[] PROGMEM = "unknown stream type";

// Set up workspace

void initworkspace () {
  Freelist = NULL;
  for (int i=WORKSPACESIZE-1; i>=0; i--) {
    object *obj = &Workspace[i];
    car(obj) = NULL;
    cdr(obj) = Freelist;
    Freelist = obj;
    Freespace++;
  }
}

object *myalloc () {
  if (Freespace == 0) { Context = NIL; error2(PSTR("no room")); }
  object *temp = Freelist;
  Freelist = cdr(Freelist);
  Freespace--;
  return temp;
}

inline void myfree (object *obj) {
  car(obj) = NULL;
  cdr(obj) = Freelist;
  Freelist = obj;
  Freespace++;
}

// Make each type of object

object *number (int n) {
  object *ptr = myalloc();
  ptr->type = NUMBER;
  ptr->integer = n;
  return ptr;
}

object *character (uint8_t c) {
  object *ptr = myalloc();
  ptr->type = CHARACTER;
  ptr->chars = c;
  return ptr;
}

object *cons (object *arg1, object *arg2) {
  object *ptr = myalloc();
  ptr->car = arg1;
  ptr->cdr = arg2;
  return ptr;
}

object *symbol (symbol_t name) {
  object *ptr = myalloc();
  ptr->type = SYMBOL;
  ptr->name = name;
  return ptr;
}

inline object *bsymbol (builtin_t name) {
  return intern(twist(name+BUILTINS));
}

object *intern (symbol_t name) {
  for (int i=0; i<WORKSPACESIZE; i++) {
    object *obj = &Workspace[i];
    if (obj->type == SYMBOL && obj->name == name) return obj;
  }
  return symbol(name);
}

bool eqsymbols (object *obj, char *buffer) {
  object *arg = cdr(obj);
  int i = 0;
  while (!(arg == NULL && buffer[i] == 0)) {
    if (arg == NULL || buffer[i] == 0 || arg->chars != (buffer[i]<<8 | buffer[i+1])) return false;
    arg = car(arg);
    i = i + 2;
  }
  return true;
}

object *internlong (char *buffer) {
  for (int i=0; i<WORKSPACESIZE; i++) {
    object *obj = &Workspace[i];
    if (obj->type == SYMBOL && longsymbolp(obj) && eqsymbols(obj, buffer)) return obj;
  }
  object *obj = lispstring(buffer);
  obj->type = SYMBOL;
  return obj;
}

object *stream (uint8_t streamtype, uint8_t address) {
  object *ptr = myalloc();
  ptr->type = STREAM;
  ptr->integer = streamtype<<8 | address;
  return ptr;
}

object *newstring () {
  object *ptr = myalloc();
  ptr->type = STRING;
  ptr->chars = 0;
  return ptr;
}


// Garbage collection

void markobject (object *obj) {
  MARK:
  if (obj == NULL) return;
  if (marked(obj)) return;

  object* arg = car(obj);
  unsigned int type = obj->type;
  mark(obj);

  if (type >= PAIR || type == ZZERO) { // cons
    markobject(arg);
    obj = cdr(obj);
    goto MARK;
  }

  if ((type == STRING) || (type == SYMBOL && longsymbolp(obj))) {
    obj = cdr(obj);
    while (obj != NULL) {
      arg = car(obj);
      mark(obj);
      obj = arg;
    }
  }
}

void sweep () {
  Freelist = NULL;
  Freespace = 0;
  for (int i=WORKSPACESIZE-1; i>=0; i--) {
    object *obj = &Workspace[i];
    if (!marked(obj)) myfree(obj); else unmark(obj);
  }
}

void gc (object *form, object *env) {
  #if defined(printgcs)
  int start = Freespace;
  #endif
  markobject(tee);
  markobject(GlobalEnv);
  markobject(GCStack);
  markobject(form);
  markobject(env);
  sweep();
  #if defined(printgcs)
  pfl(pserial); pserial('{'); pint(Freespace - start, pserial); pserial('}');
  #endif
}

// Compact image

void movepointer (object *from, object *to) {
  for (int i=0; i<WORKSPACESIZE; i++) {
    object *obj = &Workspace[i];
    unsigned int type = (obj->type) & ~MARKBIT;
    if (marked(obj) && (type >= STRING || type==ZZERO || (type == SYMBOL && longsymbolp(obj)))) {
      if (car(obj) == (object *)((uintptr_t)from | MARKBIT))
        car(obj) = (object *)((uintptr_t)to | MARKBIT);
      if (cdr(obj) == from) cdr(obj) = to;
    }
  }
  // Fix strings and long symbols
  for (int i=0; i<WORKSPACESIZE; i++) {
    object *obj = &Workspace[i];
    if (marked(obj)) {
      unsigned int type = (obj->type) & ~MARKBIT;
      if (type == STRING || (type == SYMBOL && longsymbolp(obj))) {
        obj = cdr(obj);
        while (obj != NULL) {
          if (cdr(obj) == to) cdr(obj) = from;
          obj = (object *)((uintptr_t)(car(obj)) & ~MARKBIT);
        }
      }
    }
  }
}

uintptr_t compactimage (object **arg) {
  markobject(tee);
  markobject(GlobalEnv);
  markobject(GCStack);
  object *firstfree = Workspace;
  while (marked(firstfree)) firstfree++;
  object *obj = &Workspace[WORKSPACESIZE-1];
  while (firstfree < obj) {
    if (marked(obj)) {
      car(firstfree) = car(obj);
      cdr(firstfree) = cdr(obj);
      unmark(obj);
      movepointer(obj, firstfree);
      if (GlobalEnv == obj) GlobalEnv = firstfree;
      if (GCStack == obj) GCStack = firstfree;
      if (*arg == obj) *arg = firstfree;
      while (marked(firstfree)) firstfree++;
    }
    obj--;
  }
  sweep();
  return firstfree - Workspace;
}

// Make SD card filename

char *MakeFilename (object *arg, char *buffer) {
  int max = BUFFERSIZE-1;
  int i = 0;
  do {
    char c = nthchar(arg, i);
    if (c == '\0') break;
    buffer[i++] = c;
  } while (i<max);
  buffer[i] = '\0';
  return buffer;
}

// Save-image and load-image

#if defined(sdcardsupport)
void SDWriteInt (File file, int data) {
  file.write(data & 0xFF); file.write(data>>8 & 0xFF);
}

int SDReadInt (File file) {
  uint8_t b0 = file.read(); uint8_t b1 = file.read();
  return b0 | b1<<8;
}
#elif defined(FLASHWRITESIZE)
#if defined (CPU_ATmega1284P)
// save-image area is the 16K bytes (64 256-byte pages) from 0x1bc00 to 0x1fc00
const uint32_t BaseAddress = 0x1bc00;
uint8_t FlashCheck() {
  return 0;
}

void FlashWriteInt (uint32_t *addr, int data) {
  if (((*addr) & 0xFF) == 0) optiboot_page_erase(BaseAddress + ((*addr) & 0xFF00));
  optiboot_page_fill(BaseAddress + *addr, data);
  if (((*addr) & 0xFF) == 0xFE) optiboot_page_write(BaseAddress + ((*addr) & 0xFF00));
  (*addr)++; (*addr)++;
}

void FlashEndWrite (uint32_t *addr) {
  if (((*addr) & 0xFF) != 0) optiboot_page_write((BaseAddress + ((*addr) & 0xFF00)));
}

uint8_t FlashReadByte (uint32_t *addr) {
  return pgm_read_byte_far(BaseAddress + (*addr)++);
}

int FlashReadInt (uint32_t *addr) {
  int data = pgm_read_word_far(BaseAddress + *addr);
  (*addr)++; (*addr)++;
  return data;
}
#elif defined (CPU_AVR128DX48) || defined (CPU_AVR64DD28)
// save-image area is the 16K bytes (32 512-byte pages) from 0x1c000 to 0x20000
const uint32_t BaseAddress = 0x1c000;
uint8_t FlashCheck() {
  return Flash.checkWritable();
}

void FlashWriteInt (uint32_t *addr, int data) {
  if (((*addr) & 0x1FF) == 0) Flash.erasePage(BaseAddress + ((*addr) & 0xFE00));
  Flash.writeWord(BaseAddress + *addr, data);
  (*addr)++; (*addr)++;
}

void FlashEndWrite (uint32_t *addr) {
  (void) addr;
}

uint8_t FlashReadByte (uint32_t *addr) {
  return Flash.readByte(BaseAddress + (*addr)++);
}

int FlashReadInt (uint32_t *addr) {
  int data = Flash.readWord(BaseAddress + *addr);
  (*addr)++; (*addr)++;
  return data;
}
#endif
#else
void EEPROMWriteInt (unsigned int *addr, int data) {
  EEPROM.write((*addr)++, data & 0xFF); EEPROM.write((*addr)++, data>>8 & 0xFF);
}

int EEPROMReadInt (unsigned int *addr) {
  uint8_t b0 = EEPROM.read((*addr)++); uint8_t b1 = EEPROM.read((*addr)++);
  return b0 | b1<<8;
}
#endif

unsigned int saveimage (object *arg) {
#if defined(sdcardsupport)
  unsigned int imagesize = compactimage(&arg);
  SD.begin(SDCARD_SS_PIN);
  File file;
  if (stringp(arg)) {
    char buffer[BUFFERSIZE];
    file = SD.open(MakeFilename(arg, buffer), O_RDWR | O_CREAT | O_TRUNC);
    if (!file) error2(PSTR("problem saving to SD card or invalid filename"));
    arg = NULL;
  } else if (arg == NULL || listp(arg)) {
    file = SD.open("/ULISP.IMG", O_RDWR | O_CREAT | O_TRUNC);
    if (!file) error2(PSTR("problem saving to SD card"));
  }
  else error(invalidarg, arg);
  SDWriteInt(file, (uintptr_t)arg);
  SDWriteInt(file, imagesize);
  SDWriteInt(file, (uintptr_t)GlobalEnv);
  SDWriteInt(file, (uintptr_t)GCStack);
  #if defined(CODESIZE)
  for (int i=0; i<CODESIZE; i++) file.write(MyCode[i]);
  #endif
  for (unsigned int i=0; i<imagesize; i++) {
    object *obj = &Workspace[i];
    SDWriteInt(file, (uintptr_t)car(obj));
    SDWriteInt(file, (uintptr_t)cdr(obj));
  }
  file.close();
  return imagesize;
#elif defined(FLASHWRITESIZE)
  unsigned int imagesize = compactimage(&arg);
  if (!(arg == NULL || listp(arg))) error(invalidarg, arg);
  if (FlashCheck()) error2(PSTR("flash write not supported"));
  // Save to Flash
  #if defined(CODESIZE)
  int bytesneeded = 10 + CODESIZE + imagesize*4;
  #else
  int bytesneeded = 10 + imagesize*4;
  #endif
  if (bytesneeded > FLASHWRITESIZE) error(PSTR("image too large"), number(imagesize));
  uint32_t addr = 0;
  FlashWriteInt(&addr, (uintptr_t)arg);
  FlashWriteInt(&addr, imagesize);
  FlashWriteInt(&addr, (uintptr_t)GlobalEnv);
  FlashWriteInt(&addr, (uintptr_t)GCStack);
  #if defined(CODESIZE)
  for (int i=0; i<CODESIZE/2; i++) FlashWriteInt(&addr, MyCode[i*2] | MyCode[i*2+1]<<8);
  #endif
  for (unsigned int i=0; i<imagesize; i++) {
    object *obj = &Workspace[i];
    FlashWriteInt(&addr, (uintptr_t)car(obj));
    FlashWriteInt(&addr, (uintptr_t)cdr(obj));
  }
  FlashEndWrite(&addr);
  return imagesize;
#elif defined(EEPROMSIZE)
  unsigned int imagesize = compactimage(&arg);
  if (!(arg == NULL || listp(arg))) error(invalidarg, arg);
  int bytesneeded = imagesize*4 + 10;
  if (bytesneeded > EEPROMSIZE) error(PSTR("image too large"), number(imagesize));
  unsigned int addr = 0;
  EEPROMWriteInt(&addr, (unsigned int)arg);
  EEPROMWriteInt(&addr, imagesize);
  EEPROMWriteInt(&addr, (unsigned int)GlobalEnv);
  EEPROMWriteInt(&addr, (unsigned int)GCStack);
  for (unsigned int i=0; i<imagesize; i++) {
    object *obj = &Workspace[i];
    EEPROMWriteInt(&addr, (uintptr_t)car(obj));
    EEPROMWriteInt(&addr, (uintptr_t)cdr(obj));
  }
  return imagesize;
#else
  (void) arg;
  error2(PSTR("not available"));
  return 0;
#endif
}

unsigned int loadimage (object *arg) {
#if defined(sdcardsupport)
  SD.begin(SDCARD_SS_PIN);
  File file;
  if (stringp(arg)) {
    char buffer[BUFFERSIZE];
    file = SD.open(MakeFilename(arg, buffer));
    if (!file) error2(PSTR("problem loading from SD card or invalid filename"));
  }
  else if (arg == NULL) {
    file = SD.open("/ULISP.IMG");
    if (!file) error2(PSTR("problem loading from SD card"));
  }
  else error(invalidarg, arg);
  SDReadInt(file);
  unsigned int imagesize = SDReadInt(file);
  GlobalEnv = (object *)SDReadInt(file);
  GCStack = (object *)SDReadInt(file);
  #if defined(CODESIZE)
  for (int i=0; i<CODESIZE; i++) MyCode[i] = file.read();
  #endif
  for (unsigned int i=0; i<imagesize; i++) {
    object *obj = &Workspace[i];
    car(obj) = (object *)SDReadInt(file);
    cdr(obj) = (object *)SDReadInt(file);
  }
  file.close();
  gc(NULL, NULL);
  return imagesize;
#elif defined(FLASHWRITESIZE)
  (void) arg;
  if (FlashCheck()) error2(PSTR("flash write not supported"));
  uint32_t addr = 0;
  FlashReadInt(&addr); // Skip eval address
  unsigned int imagesize = FlashReadInt(&addr);
  if (imagesize == 0 || imagesize == 0xFFFF) error2(PSTR("no saved image"));
  GlobalEnv = (object *)FlashReadInt(&addr);
  GCStack = (object *)FlashReadInt(&addr);
  #if defined(CODESIZE)
  for (int i=0; i<CODESIZE; i++) MyCode[i] = FlashReadByte(&addr);
  #endif
  for (unsigned int i=0; i<imagesize; i++) {
    object *obj = &Workspace[i];
    car(obj) = (object *)FlashReadInt(&addr);
    cdr(obj) = (object *)FlashReadInt(&addr);
  }
  gc(NULL, NULL);
  return imagesize;
#elif defined(EEPROMSIZE)
  (void) arg;
  unsigned int addr = 2; // Skip eval address
  unsigned int imagesize = EEPROMReadInt(&addr);
  if (imagesize == 0 || imagesize == 0xFFFF) error2(PSTR("no saved image"));
  GlobalEnv = (object *)EEPROMReadInt(&addr);
  GCStack = (object *)EEPROMReadInt(&addr);
  for (unsigned int i=0; i<imagesize; i++) {
    object *obj = &Workspace[i];
    car(obj) = (object *)EEPROMReadInt(&addr);
    cdr(obj) = (object *)EEPROMReadInt(&addr);
  }
  gc(NULL, NULL);
  return imagesize;
#else
  (void) arg;
  error2(PSTR("not available"));
  return 0;
#endif
}

void autorunimage () {
#if defined(sdcardsupport)
  SD.begin(SDCARD_SS_PIN);
  File file = SD.open("ULISP.IMG");
  if (!file) error2(PSTR("problem autorunning from SD card"));
  object *autorun = (object *)SDReadInt(file);
  file.close();
  if (autorun != NULL) {
    loadimage(NULL);
    apply(autorun, NULL, NULL);
  }
#elif defined(FLASHWRITESIZE)
  uint32_t addr = 0;
  object *autorun = (object *)FlashReadInt(&addr);
  if (autorun != NULL && (unsigned int)autorun != 0xFFFF) {
    loadimage(nil);
    apply(autorun, NULL, NULL);
  }
#elif defined(EEPROMSIZE)
  unsigned int addr = 0;
  object *autorun = (object *)EEPROMReadInt(&addr);
  if (autorun != NULL && (unsigned int)autorun != 0xFFFF) {
    loadimage(nil);
    apply(autorun, NULL, NULL);
  }
#else
  error2(PSTR("not available"));
#endif
}

// Tracing

int tracing (symbol_t name) {
  int i = 0;
  while (i < TRACEMAX) {
    if (TraceFn[i] == name) return i+1;
    i++;
  }
  return 0;
}

void trace (symbol_t name) {
  if (tracing(name)) error(PSTR("already being traced"), symbol(name));
  int i = 0;
  while (i < TRACEMAX) {
    if (TraceFn[i] == 0) { TraceFn[i] = name; TraceDepth[i] = 0; return; }
    i++;
  }
  error2(PSTR("already tracing " stringify(TRACEMAX) " functions"));
}

void untrace (symbol_t name) {
  int i = 0;
  while (i < TRACEMAX) {
    if (TraceFn[i] == name) { TraceFn[i] = 0; return; }
    i++;
  }
  error(PSTR("not tracing"), symbol(name));
}

// Helper functions

bool consp (object *x) {
  if (x == NULL) return false;
  unsigned int type = x->type;
  return type >= PAIR || type == ZZERO;
}

#define atom(x) (!consp(x))

bool listp (object *x) {
  if (x == NULL) return true;
  unsigned int type = x->type;
  return type >= PAIR || type == ZZERO;
}

#define improperp(x) (!listp(x))

object *quote (object *arg) {
  return cons(bsymbol(QUOTE), cons(arg,NULL));
}

// Radix 40 encoding

builtin_t builtin (symbol_t name) {
  return (builtin_t)(untwist(name) - BUILTINS);
}

symbol_t sym (builtin_t x) {
  return twist(x + BUILTINS);
}

int8_t toradix40 (char ch) {
  if (ch == 0) return 0;
  if (ch >= '0' && ch <= '9') return ch-'0'+1;
  if (ch == '-') return 37; if (ch == '*') return 38; if (ch == '$') return 39;
  ch = ch | 0x20;
  if (ch >= 'a' && ch <= 'z') return ch-'a'+11;
  return -1; // Invalid
}

char fromradix40 (char n) {
  if (n >= 1 && n <= 10) return '0'+n-1;
  if (n >= 11 && n <= 36) return 'a'+n-11;
  if (n == 37) return '-'; if (n == 38) return '*'; if (n == 39) return '$';
  return 0;
}

uint16_t pack40 (char *buffer) {
  return (((toradix40(buffer[0]) * 40) + toradix40(buffer[1])) * 40 + toradix40(buffer[2]));
}

bool valid40 (char *buffer) {
 return (toradix40(buffer[0]) >= 11 && toradix40(buffer[1]) >= 0 && toradix40(buffer[2]) >= 0);
}

int8_t digitvalue (char d) {
  if (d>='0' && d<='9') return d-'0';
  d = d | 0x20;
  if (d>='a' && d<='f') return d-'a'+10;
  return 16;
}

int checkinteger (object *obj) {
  if (!integerp(obj)) error(notaninteger, obj);
  return obj->integer;
}

int checkchar (object *obj) {
  if (!characterp(obj)) error(PSTR("argument is not a character"), obj);
  return obj->chars;
}

object *checkstring (object *obj) {
  if (!stringp(obj)) error(notastring, obj);
  return obj;
}

int isstream (object *obj){
  if (!streamp(obj)) error(PSTR("not a stream"), obj);
  return obj->integer;
}

int isbuiltin (object *obj, builtin_t n) {
  return symbolp(obj) && obj->name == sym(n);
}

bool builtinp (symbol_t name) {
  return (untwist(name) >= BUILTINS);
}

int checkkeyword (object *obj) {
  if (!keywordp(obj)) error(PSTR("argument is not a keyword"), obj);
  builtin_t kname = builtin(obj->name);
  uint8_t context = getminmax(kname);
  if (context != 0 && context != Context) error(invalidkey, obj);
  return ((int)lookupfn(kname));
}

void checkargs (object *args) {
  int nargs = listlength(args);
  checkminmax(Context, nargs);
}

boolean eq (object *arg1, object *arg2) {
  if (arg1 == arg2) return true;  // Same object
  if ((arg1 == nil) || (arg2 == nil)) return false;  // Not both values
  if (arg1->cdr != arg2->cdr) return false;  // Different values
  if (symbolp(arg1) && symbolp(arg2)) return true;  // Same symbol
  if (integerp(arg1) && integerp(arg2)) return true;  // Same integer
  if (characterp(arg1) && characterp(arg2)) return true;  // Same character
  return false;
}

bool equal (object *arg1, object *arg2) {
  if (stringp(arg1) && stringp(arg2)) return stringcompare(cons(arg1, cons(arg2, nil)), false, false, true);
  if (consp(arg1) && consp(arg2)) return (equal(car(arg1), car(arg2)) && equal(cdr(arg1), cdr(arg2)));
  return eq(arg1, arg2);
}

int listlength (object *list) {
  int length = 0;
  while (list != NULL) {
    if (improperp(list)) error2(notproper);
    list = cdr(list);
    length++;
  }
  return length;
}

object *checkarguments (object *args, uint8_t min, uint8_t max) {
  if (args == NULL) error2(noargument);
  args = first(args);
  if (!listp(args)) error(notalist, args);
  uint8_t length = listlength(args);
  if (length < min) error(toofewargs, args);
  if (length > max) error(toomanyargs, args);
  return args;
}

// Mathematical helper functions

uint16_t pseudoRandom (int range) {
  if (RandomSeed == 0) RandomSeed++;
  uint16_t l = RandomSeed & 1;
  RandomSeed = RandomSeed >> 1;
  if (l == 1) RandomSeed = RandomSeed ^ 0xD295;
  int dummy; if (RandomSeed == 0) Serial.print((int)&dummy); // Do not remove!
  return RandomSeed % range;
}

object *compare (object *args, bool lt, bool gt, bool eq) {
  int arg1 = checkinteger(first(args));
  args = cdr(args);
  while (args != NULL) {
    int arg2 = checkinteger(first(args));
    if (!lt && (arg1 < arg2)) return nil;
    if (!eq && (arg1 == arg2)) return nil;
    if (!gt && (arg1 > arg2)) return nil;
    arg1 = arg2;
    args = cdr(args);
  }
  return tee;
}

int intpower (int base, int exp) {
  int result = 1;
  while (exp) {
    if (exp & 1) result = result * base;
    exp = exp / 2;
    base = base * base;
  }
  return result;
}

// Association lists

object *delassoc (object *key, object **alist) {
  object *list = *alist;
  object *prev = NULL;
  while (list != NULL) {
    object *pair = first(list);
    if (eq(key,car(pair))) {
      if (prev == NULL) *alist = cdr(list);
      else cdr(prev) = cdr(list);
      return key;
    }
    prev = list;
    list = cdr(list);
  }
  return nil;
}

// String utilities

void indent (uint8_t spaces, char ch, pfun_t pfun) {
  for (uint8_t i=0; i<spaces; i++) pfun(ch);
}

object *startstring () {
  object *string = newstring();
  GlobalString = string;
  GlobalStringTail = string;
  return string;
}

object *princtostring (object *arg) {
  object *obj = startstring();
  prin1object(arg, pstr);
  return obj;
}

void buildstring (char ch, object **tail) {
  object *cell;
  if (cdr(*tail) == NULL) {
    cell = myalloc(); cdr(*tail) = cell;
  } else if (((*tail)->chars & 0xFF) == 0) {
    (*tail)->chars |= ch; return;
  } else {
    cell = myalloc(); car(*tail) = cell;
  }
  car(cell) = NULL; cell->chars = ch<<8; *tail = cell;
}

object *copystring (object *arg) {
  object *obj = newstring();
  object *ptr = obj;
  arg = cdr(arg);
  while (arg != NULL) {
    object *cell =  myalloc(); car(cell) = NULL;
    if (cdr(obj) == NULL) cdr(obj) = cell; else car(ptr) = cell;
    ptr = cell;
    ptr->chars = arg->chars;
    arg = car(arg);
  }
  return obj;
}

object *readstring (uint8_t delim, bool esc, gfun_t gfun) {
  object *obj = newstring();
  object *tail = obj;
  int ch = gfun();
  if (ch == -1) return nil;
  while ((ch != delim) && (ch != -1)) {
    if (esc && ch == '\\') ch = gfun();
    buildstring(ch, &tail);
    ch = gfun();
  }
  return obj;
}

int stringlength (object *form) {
  int length = 0;
  form = cdr(form);
  while (form != NULL) {
    int chars = form->chars;
    for (int i=(sizeof(int)-1)*8; i>=0; i=i-8) {
      if (chars>>i & 0xFF) length++;
    }
    form = car(form);
  }
  return length;
}

uint8_t nthchar (object *string, int n) {
  object *arg = cdr(string);
  int top;
  if (sizeof(int) == 4) { top = n>>2; n = 3 - (n&3); }
  else { top = n>>1; n = 1 - (n&1); }
  for (int i=0; i<top; i++) {
    if (arg == NULL) return 0;
    arg = car(arg);
  }
  if (arg == NULL) return 0;
  return (arg->chars)>>(n*8) & 0xFF;
}

int gstr () {
  if (LastChar) {
    char temp = LastChar;
    LastChar = 0;
    return temp;
  }
  char c = nthchar(GlobalString, GlobalStringIndex++);
  if (c != 0) return c;
  return '\n'; // -1?
}

void pstr (char c) {
  buildstring(c, &GlobalStringTail);
}

object *lispstring (char *s) {
  object *obj = newstring();
  object *tail = obj;
  while(1) {
    char ch = *s++;
    if (ch == 0) break;
    if (ch == '\\') ch = *s++;
    buildstring(ch, &tail);
  }
  return obj;
}

bool stringcompare (object *args, bool lt, bool gt, bool eq) {
  object *arg1 = checkstring(first(args));
  object *arg2 = checkstring(second(args));
  arg1 = cdr(arg1);
  arg2 = cdr(arg2);
  while ((arg1 != NULL) || (arg2 != NULL)) {
    if (arg1 == NULL) return lt;
    if (arg2 == NULL) return gt;
    if (arg1->chars < arg2->chars) return lt;
    if (arg1->chars > arg2->chars) return gt;
    arg1 = car(arg1);
    arg2 = car(arg2);
  }
  return eq;
}

// Lookup variable in environment

object *value (symbol_t n, object *env) {
  while (env != NULL) {
    object *pair = car(env);
    if (pair != NULL && car(pair)->name == n) return pair;
    env = cdr(env);
  }
  return nil;
}

object *findpair (object *var, object *env) {
  symbol_t name = var->name;
  object *pair = value(name, env);
  if (pair == NULL) pair = value(name, GlobalEnv);
  return pair;
}

bool boundp (object *var, object *env) {
  if (!symbolp(var)) error(notasymbol, var);
  return (findpair(var, env) != NULL);
}

object *findvalue (object *var, object *env) {
  object *pair = findpair(var, env);
  if (pair == NULL) error(PSTR("unknown variable"), var);
  return pair;
}

// Handling closures

object *closure (int tc, symbol_t name, object *function, object *args, object **env) {
  object *state = car(function);
  function = cdr(function);
  int trace = 0;
  if (name) trace = tracing(name);
  if (trace) {
    indent(TraceDepth[trace-1]<<1, ' ', pserial);
    pint(TraceDepth[trace-1]++, pserial);
    pserial(':'); pserial(' '); pserial('('); printsymbol(symbol(name), pserial);
  }
  object *params = first(function);
  if (!listp(params)) errorsym(name, notalist, params);
  function = cdr(function);
  // Dropframe
  if (tc) {
    if (*env != NULL && car(*env) == NULL) {
      pop(*env);
      while (*env != NULL && car(*env) != NULL) pop(*env);
    } else push(nil, *env);
  }
  // Push state
  while (consp(state)) {
    object *pair = first(state);
    push(pair, *env);
    state = cdr(state);
  }
  // Add arguments to environment
  bool optional = false;
  while (params != NULL) {
    object *value;
    object *var = first(params);
    if (isbuiltin(var, OPTIONAL)) optional = true;
    else {
      if (consp(var)) {
        if (!optional) errorsym(name, PSTR("invalid default value"), var);
        if (args == NULL) value = eval(second(var), *env);
        else { value = first(args); args = cdr(args); }
        var = first(var);
        if (!symbolp(var)) errorsym(name, PSTR("illegal optional parameter"), var);
      } else if (!symbolp(var)) {
        errorsym(name, PSTR("illegal function parameter"), var);
      } else if (isbuiltin(var, AMPREST)) {
        params = cdr(params);
        var = first(params);
        value = args;
        args = NULL;
      } else {
        if (args == NULL) {
          if (optional) value = nil;
          else errorsym2(name, toofewargs);
        } else { value = first(args); args = cdr(args); }
      }
      push(cons(var,value), *env);
      if (trace) { pserial(' '); printobject(value, pserial); }
    }
    params = cdr(params);
  }
  if (args != NULL) errorsym2(name, toomanyargs);
  if (trace) { pserial(')'); pln(pserial); }
  // Do an implicit progn
  if (tc) push(nil, *env);
  return tf_progn(function, *env);
}

object *apply (object *function, object *args, object *env) {
  if (symbolp(function)) {
    builtin_t fname = builtin(function->name);
    if ((fname < ENDFUNCTIONS) && ((getminmax(fname)>>6) == FUNCTIONS)) {
      Context = fname;
      checkargs(args);
      return ((fn_ptr_type)lookupfn(fname))(args, env);
    } else function = eval(function, env);
  }
  if (consp(function) && isbuiltin(car(function), LAMBDA)) {
    object *result = closure(0, sym(NIL), function, args, &env);
    return eval(result, env);
  }
  if (consp(function) && isbuiltin(car(function), CLOSURE)) {
    function = cdr(function);
    object *result = closure(0, sym(NIL), function, args, &env);
    return eval(result, env);
  }
  error(PSTR("illegal function"), function);
  return NULL;
}

// In-place operations

object **place (object *args, object *env, int *bit) {
  if (atom(args)) return &cdr(findvalue(args, env));
  object* function = first(args);
  if (symbolp(function)) {
    symbol_t sname = function->name;
    if (sname == sym(CAR) || sname == sym(FIRST)) {
      object *value = eval(second(args), env);
      if (!listp(value)) error(canttakecar, value);
      return &car(value);
    }
    if (sname == sym(CDR) || sname == sym(REST)) {
      object *value = eval(second(args), env);
      if (!listp(value)) error(canttakecdr, value);
      return &cdr(value);
    }
    if (sname == sym(NTH)) {
      int index = checkinteger(eval(second(args), env));
      object *list = eval(third(args), env);
      if (atom(list)) { Context = NTH; error(PSTR("second argument is not a list"), list); }
      int i = index;
      while (i > 0) {
        list = cdr(list);
        if (list == NULL) { Context = NTH; error(indexrange, number(index)); }
        i--;
      }
      return &car(list);
    }
  }
  error2(PSTR("illegal place"));
  return nil;
}

object *incfdecf (object *args, int increment, object *env) {
  int bit;
  object **loc = place(first(args), env, &bit);
  if (bit < -1) error2(notanumber);
  int result = checkinteger(*loc);
  args = cdr(args);
  if (args != NULL) increment = checkinteger(eval(first(args), env)) * increment;
  #if defined(checkoverflow)
  if (increment < 1) { if (INT_MIN - increment > result) error2(overflow); }
  else { if (INT_MAX - increment < result) error2(overflow); }
  #endif
  result = result + increment;
  *loc = number(result);
  return *loc;
}

// Checked car and cdr

object *carx (object *arg) {
  if (!listp(arg)) error(canttakecar, arg);
  if (arg == nil) return nil;
  return car(arg);
}

object *cdrx (object *arg) {
  if (!listp(arg)) error(canttakecdr, arg);
  if (arg == nil) return nil;
  return cdr(arg);
}

object *cxxxr (object *args, uint8_t pattern) {
  object *arg = first(args);
  while (pattern != 1) {
    if ((pattern & 1) == 0) arg = carx(arg); else arg = cdrx(arg);
    pattern = pattern>>1;
  }
  return arg;
}

// Mapping helper functions

object *mapcl (object *args, object *env, bool mapl) {
  object *function = first(args);
  args = cdr(args);
  object *result = first(args);
  protect(result);
  object *params = cons(NULL, NULL);
  protect(params);
  // Make parameters
  while (true) {
    object *tailp = params;
    object *lists = args;
    while (lists != NULL) {
      object *list = car(lists);
      if (list == NULL) {
         unprotect(); unprotect();
         return result;
      }
      if (improperp(list)) error(notproper, list);
      object *item = mapl ? list : first(list);
      object *obj = cons(item, NULL);
      car(lists) = cdr(list);
      cdr(tailp) = obj; tailp = obj;
      lists = cdr(lists);
    }
    apply(function, cdr(params), env);
  }
}

void mapcarfun (object *result, object **tail) {
  object *obj = cons(result,NULL);
  cdr(*tail) = obj; *tail = obj;
}

void mapcanfun (object *result, object **tail) {
  if (cdr(*tail) != NULL) error(notproper, *tail);
  while (consp(result)) {
    cdr(*tail) = result; *tail = result;
    result = cdr(result);
  }
}

object *mapcarcan (object *args, object *env, mapfun_t fun, bool maplist) {
  object *function = first(args);
  args = cdr(args);
  object *params = cons(NULL, NULL);
  protect(params);
  object *head = cons(NULL, NULL);
  protect(head);
  object *tail = head;
  // Make parameters
  while (true) {
    object *tailp = params;
    object *lists = args;
    while (lists != NULL) {
      object *list = car(lists);
      if (list == NULL) {
         unprotect(); unprotect();
         return cdr(head);
      }
      if (improperp(list)) error(notproper, list);
      object *item = maplist ? list : first(list);
      object *obj = cons(item, NULL);
      car(lists) = cdr(list);
      cdr(tailp) = obj; tailp = obj;
      lists = cdr(lists);
    }
    object *result = apply(function, cdr(params), env);
    fun(result, &tail);
  }
}

// I2C interface for AVR platforms, uses much less RAM than Arduino Wire

#if defined(CPU_ATmega328P)
uint8_t const TWI_SDA_PIN = 18;
uint8_t const TWI_SCL_PIN = 19;
#elif defined(CPU_ATmega1280) || defined(CPU_ATmega2560)
uint8_t const TWI_SDA_PIN = 20;
uint8_t const TWI_SCL_PIN = 21;
#elif defined(CPU_ATmega644P) || defined(CPU_ATmega1284P)
uint8_t const TWI_SDA_PIN = 17;
uint8_t const TWI_SCL_PIN = 16;
#elif defined(CPU_ATmega32U4)
uint8_t const TWI_SDA_PIN = 6;
uint8_t const TWI_SCL_PIN = 5;
#endif

#if defined(CPU_ATmega4809) || defined(CPU_AVR128DX48) || defined(CPU_ATtiny3227)
uint32_t const FREQUENCY = 400000L;  // Hardware I2C clock in Hz
uint32_t const T_RISE = 300L;        // Rise time
#else
uint32_t const F_TWI = 400000L;  // Hardware I2C clock in Hz
uint8_t const TWSR_MTX_DATA_ACK = 0x28;
uint8_t const TWSR_MTX_ADR_ACK = 0x18;
uint8_t const TWSR_MRX_ADR_ACK = 0x40;
uint8_t const TWSR_START = 0x08;
uint8_t const TWSR_REP_START = 0x10;
uint8_t const I2C_READ = 1;
uint8_t const I2C_WRITE = 0;
#endif

void I2Cinit (bool enablePullup) {
#if defined(CPU_ATmega4809) || defined(CPU_AVR128DX48) || defined(CPU_ATtiny3227)
  #if defined(CPU_ATmega4809)
  if (enablePullup) {
    pinMode(SDA, INPUT_PULLUP);
    pinMode(SCL, INPUT_PULLUP);
  }
  #else
  (void) enablePullup;
  #endif
  uint32_t baud = ((F_CPU/FREQUENCY) - (((F_CPU*T_RISE)/1000)/1000)/1000 - 10)/2;
  TWI0.MBAUD = (uint8_t)baud;
  TWI0.MCTRLA = TWI_ENABLE_bm;                                    // Enable as master, no interrupts
  TWI0.MSTATUS = TWI_BUSSTATE_IDLE_gc;
#else
  TWSR = 0;                        // no prescaler
  TWBR = (F_CPU/F_TWI - 16)/2;     // set bit rate factor
  if (enablePullup) {
    digitalWrite(SDA, HIGH);
    digitalWrite(SCL, HIGH);
  }
#endif
}

int I2Cread () {
#if defined(CPU_ATmega4809) || defined(CPU_AVR128DX48) || defined(CPU_ATtiny3227)
  if (I2Ccount != 0) I2Ccount--;
  while (!(TWI0.MSTATUS & TWI_RIF_bm));                           // Wait for read interrupt flag
  uint8_t data = TWI0.MDATA;
  // Check slave sent ACK?
  if (I2Ccount != 0) TWI0.MCTRLB = TWI_MCMD_RECVTRANS_gc;         // ACK = more bytes to read
  else TWI0.MCTRLB = TWI_ACKACT_NACK_gc;                          // Send NAK
  return data;
#else
  if (I2Ccount != 0) I2Ccount--;
  TWCR = 1<<TWINT | 1<<TWEN | ((I2Ccount == 0) ? 0 : (1<<TWEA));
  while (!(TWCR & 1<<TWINT));
  return TWDR;
#endif
}

bool I2Cwrite (uint8_t data) {
#if defined(CPU_ATmega4809) || defined(CPU_AVR128DX48) || defined(CPU_ATtiny3227)
  TWI0.MCTRLB = TWI_MCMD_RECVTRANS_gc;                            // Prime transaction
  TWI0.MDATA = data;                                              // Send data
  while (!(TWI0.MSTATUS & TWI_WIF_bm));                           // Wait for write to complete

  if (TWI0.MSTATUS & (TWI_ARBLOST_bm | TWI_BUSERR_bm)) return false; // Fails if bus error or arblost
  return !(TWI0.MSTATUS & TWI_RXACK_bm);                          // Returns true if slave gave an ACK
#else
  TWDR = data;
  TWCR = 1<<TWINT | 1 << TWEN;
  while (!(TWCR & 1<<TWINT));
  return (TWSR & 0xF8) == TWSR_MTX_DATA_ACK;
#endif
}

bool I2Cstart (uint8_t address, uint8_t read) {
#if defined(CPU_ATmega4809) || defined(CPU_AVR128DX48) || defined(CPU_ATtiny3227)
  TWI0.MADDR = address<<1 | read;                                 // Send START condition
  while (!(TWI0.MSTATUS & (TWI_WIF_bm | TWI_RIF_bm)));            // Wait for write or read interrupt flag
  if (TWI0.MSTATUS & TWI_ARBLOST_bm) {                            // Arbitration lost or bus error
    while (!((TWI0.MSTATUS & TWI_BUSSTATE_gm) == TWI_BUSSTATE_IDLE_gc)); // Wait for bus to return to idle state
    return false;
  } else if (TWI0.MSTATUS & TWI_RXACK_bm) {                       // Address not acknowledged by client
    TWI0.MCTRLB |= TWI_MCMD_STOP_gc;                              // Send stop condition
    while (!((TWI0.MSTATUS & TWI_BUSSTATE_gm) == TWI_BUSSTATE_IDLE_gc)); // Wait for bus to return to idle state
    return false;
  }
  return true;                                                    // Return true if slave gave an ACK
#else
  uint8_t addressRW = address<<1 | read;
  TWCR = 1<<TWINT | 1<<TWSTA | 1<<TWEN;    // Send START condition
  while (!(TWCR & 1<<TWINT));
  if ((TWSR & 0xF8) != TWSR_START && (TWSR & 0xF8) != TWSR_REP_START) return false;
  TWDR = addressRW;  // send device address and direction
  TWCR = 1<<TWINT | 1<<TWEN;
  while (!(TWCR & 1<<TWINT));
  if (addressRW & I2C_READ) return (TWSR & 0xF8) == TWSR_MRX_ADR_ACK;
  else return (TWSR & 0xF8) == TWSR_MTX_ADR_ACK;
#endif
}

bool I2Crestart (uint8_t address, uint8_t read) {
  return I2Cstart(address, read);
}

void I2Cstop (uint8_t read) {
#if defined(CPU_ATmega4809) || defined(CPU_AVR128DX48) || defined(CPU_ATtiny3227)
  (void) read;
  TWI0.MCTRLB |= TWI_MCMD_STOP_gc;                                // Send STOP
  while (!((TWI0.MSTATUS & TWI_BUSSTATE_gm) == TWI_BUSSTATE_IDLE_gc)); // Wait for bus to return to idle state
#else
  (void) read;
  TWCR = 1<<TWINT | 1<<TWEN | 1<<TWSTO;
  while (TWCR & 1<<TWSTO); // wait until stop and bus released
#endif
}

// Streams

inline int spiread () { return SPI.transfer(0); }
#if defined(CPU_ATmega1284P) || defined(CPU_AVR128DX48) || defined(CPU_AVR64DD28)
inline int serial1read () { while (!Serial1.available()) testescape(); return Serial1.read(); }
#elif defined(CPU_ATmega2560)
inline int serial1read () { while (!Serial1.available()) testescape(); return Serial1.read(); }
inline int serial2read () { while (!Serial2.available()) testescape(); return Serial2.read(); }
inline int serial3read () { while (!Serial3.available()) testescape(); return Serial3.read(); }
#endif
#if defined(sdcardsupport)
File SDpfile, SDgfile;
inline int SDread () {
  if (LastChar) { 
    char temp = LastChar;
    LastChar = 0;
    return temp;
  }
  return SDgfile.read();
}
#endif

void serialbegin (int address, int baud) {
  #if defined(CPU_ATmega328P) || defined(CPU_ATmega4809) || defined(CPU_AVR64DD28)
  (void) address; (void) baud;
  #elif defined(CPU_ATmega1284P) || defined(CPU_AVR128DX48)
  if (address == 1) Serial1.begin((long)baud*100);
  else error(PSTR("port not supported"), number(address));
  #elif defined(CPU_ATmega2560)
  if (address == 1) Serial1.begin((long)baud*100);
  else if (address == 2) Serial2.begin((long)baud*100);
  else if (address == 3) Serial3.begin((long)baud*100);
  else error(PSTR("port not supported"), number(address));
  #endif
}

void serialend (int address) {
  #if defined(CPU_ATmega328P) || defined(CPU_ATmega4809) || defined(CPU_AVR64DD28)
  (void) address;
  #elif defined(CPU_ATmega1284P) || defined(CPU_AVR128DX48)
  if (address == 1) {Serial1.flush(); Serial1.end(); }
  #elif defined(CPU_ATmega2560)
  if (address == 1) {Serial1.flush(); Serial1.end(); }
  else if (address == 2) {Serial2.flush(); Serial2.end(); }
  else if (address == 3) {Serial3.flush(); Serial3.end(); }
  #endif
}

gfun_t gstreamfun (object *args) {
  int streamtype = SERIALSTREAM;
  int address = 0;
  gfun_t gfun = gserial;
  if (args != NULL) {
    int stream = isstream(first(args));
    streamtype = stream>>8; address = stream & 0xFF;
  }
  if (streamtype == I2CSTREAM) gfun = (gfun_t)I2Cread;
  else if (streamtype == SPISTREAM) gfun = spiread;
  else if (streamtype == SERIALSTREAM) {
    if (address == 0) gfun = gserial;
    #if defined(CPU_ATmega1284P) || defined(CPU_AVR128DX48)
    else if (address == 1) gfun = serial1read;
    #elif defined(CPU_ATmega2560)
    else if (address == 1) gfun = serial1read;
    else if (address == 2) gfun = serial2read;
    else if (address == 3) gfun = serial3read;
    #endif
  }
  #if defined(sdcardsupport)
  else if (streamtype == SDSTREAM) gfun = (gfun_t)SDread;
  #endif
  else error2(unknownstreamtype);
  return gfun;
}

inline void spiwrite (char c) { SPI.transfer(c); }
#if defined(CPU_ATmega1284P) || defined(CPU_AVR128DX48)
inline void serial1write (char c) { Serial1.write(c); }
#elif defined(CPU_ATmega2560)
inline void serial1write (char c) { Serial1.write(c); }
inline void serial2write (char c) { Serial2.write(c); }
inline void serial3write (char c) { Serial3.write(c); }
#endif
#if defined(sdcardsupport)
inline void SDwrite (char c) { int w = SDpfile.write(c); if (w != 1) { Context = NIL; error2(PSTR("failed to write to file")); } }
#endif

pfun_t pstreamfun (object *args) {
  int streamtype = SERIALSTREAM;
  int address = 0;
  pfun_t pfun = pserial;
  if (args != NULL && first(args) != NULL) {
    int stream = isstream(first(args));
    streamtype = stream>>8; address = stream & 0xFF;
  }
  if (streamtype == I2CSTREAM) pfun = (pfun_t)I2Cwrite;
  else if (streamtype == SPISTREAM) pfun = spiwrite;
  else if (streamtype == SERIALSTREAM) {
    if (address == 0) pfun = pserial;
    #if defined(CPU_ATmega1284P) || defined(CPU_AVR128DX48)
    else if (address == 1) pfun = serial1write;
    #elif defined(CPU_ATmega2560)
    else if (address == 1) pfun = serial1write;
    else if (address == 2) pfun = serial2write;
    else if (address == 3) pfun = serial3write;
    #endif
  }   
  else if (streamtype == STRINGSTREAM) {
    pfun = pstr;
  }
  #if defined(sdcardsupport)
  else if (streamtype == SDSTREAM) pfun = (pfun_t)SDwrite;
  #endif
  else error2(unknownstreamtype);
  return pfun;
}

// Check pins - these are board-specific not processor-specific

void checkanalogread (int pin) {
#if defined(ARDUINO_AVR_UNO)
  if (!(pin>=0 && pin<=5)) error(invalidpin, number(pin));
#elif defined(ARDUINO_AVR_MEGA2560)
  if (!(pin>=0 && pin<=15)) error(invalidpin, number(pin));
#elif defined(__AVR_ATmega1284P__)
  if (!(pin>=0 && pin<=7)) error(invalidpin, number(pin));
#elif defined(ARDUINO_AVR_NANO_EVERY)
  if (!((pin>=14 && pin<=21))) error(invalidpin, number(pin));
#elif defined(ARDUINO_AVR_ATmega4809)  /* MegaCoreX core */
  if (!((pin>=22 && pin<=33) || (pin>=36 && pin<=39))) error(invalidpin, number(pin));
#elif defined(ARDUINO_AVR_ATtiny3227)
  if (!((pin>=0 && pin<=3) || (pin>=6 && pin<=7) || (pin>=10 && pin<=11) || pin==18)) error(invalidpin, number(pin));
#elif defined(__AVR_AVR128DA48__)
  if (!(pin>=22 && pin<=39)) error(invalidpin, number(pin));
#endif
}

void checkanalogwrite (int pin) {
#if defined(ARDUINO_AVR_UNO)
  if (!(pin==3 || pin==5 || pin==6 || (pin>=9 && pin<=11))) error(invalidpin, number(pin));
#elif defined(ARDUINO_AVR_MEGA2560)
  if (!((pin>=2 && pin<=13) || (pin>=44 && pin<=46))) error(invalidpin, number(pin));
#elif defined(__AVR_ATmega1284P__)
  if (!(pin==3 || pin==4 || pin==6 || pin==7 || (pin>=12 && pin<=15))) error(invalidpin, number(pin));
#elif defined(ARDUINO_AVR_NANO_EVERY)
  if (!(pin==3 || pin==5 || pin==6 || pin==9 || pin==10)) error(invalidpin, number(pin));
#elif defined(ARDUINO_AVR_ATmega4809)  /* MegaCoreX core */
  if (!((pin>=16 && pin<=19) || (pin>=38 && pin<=39))) error(invalidpin, number(pin));
#elif defined(ARDUINO_AVR_ATtiny3227)
  if (!((pin>=0 && pin<=1) || (pin>=9 && pin<=11) || pin==20)) error(invalidpin, number(pin));
#elif defined(__AVR_AVR128DA48__)
  if (!((pin>=4 && pin<=5) || (pin>=8 && pin<=19) || (pin>=38 && pin<=39))) error(invalidpin, number(pin));
#endif
}

// Note

#if defined(CPU_ATmega4809) || defined(CPU_AVR128DX48) || defined(CPU_ATtiny3227)
const int scale[] PROGMEM = {4186,4435,4699,4978,5274,5588,5920,6272,6645,7040,7459,7902};
#else
const uint8_t scale[] PROGMEM = {239,226,213,201,190,179,169,160,151,142,134,127};
#endif

void playnote (int pin, int note, int octave) {
#if defined(CPU_ATmega328P)
  if (pin == 3) {
    DDRD = DDRD | 1<<DDD3; // PD3 (Arduino D3) as output
    TCCR2A = 0<<COM2A0 | 1<<COM2B0 | 2<<WGM20; // Toggle OC2B on match
  } else if (pin == 11) {
    DDRB = DDRB | 1<<DDB3; // PB3 (Arduino D11) as output
    TCCR2A = 1<<COM2A0 | 0<<COM2B0 | 2<<WGM20; // Toggle OC2A on match
  } else error(PSTR("only pins 3 and 11 supported"), number(pin));
  int oct = octave + note/12;
  int prescaler = 9 - oct;
  if (prescaler<3 || prescaler>6) error(PSTR("octave out of range"), number(oct));
  OCR2A = pgm_read_byte(&scale[note%12]) - 1;
  TCCR2B = 0<<WGM22 | prescaler<<CS20;

#elif defined(CPU_ATmega2560)
  if (pin == 9) {
    DDRH = DDRH | 1<<DDH6; // PH6 (Arduino D9) as output
    TCCR2A = 0<<COM2A0 | 1<<COM2B0 | 2<<WGM20; // Toggle OC2B on match
  } else if (pin == 10) {
    DDRB = DDRB | 1<<DDB4; // PB4 (Arduino D10) as output
    TCCR2A = 1<<COM2A0 | 0<<COM2B0 | 2<<WGM20; // Toggle OC2A on match
  } else error(PSTR("only pins 9 and 10 supported"), number(pin));
  int oct = octave + note/12;
  int prescaler = 9 - oct;
  if (prescaler<3 || prescaler>6) error(PSTR("octave out of range"), number(oct));
  OCR2A = pgm_read_byte(&scale[note%12]) - 1;
  TCCR2B = 0<<WGM22 | prescaler<<CS20;

#elif defined(CPU_ATmega1284P)
  if (pin == 14) {
    DDRD = DDRD | 1<<DDD6; // PD6 (Arduino D14) as output
    TCCR2A = 0<<COM2A0 | 1<<COM2B0 | 2<<WGM20; // Toggle OC2B on match
  } else if (pin == 15) {
    DDRD = DDRD | 1<<DDD7; // PD7 (Arduino D15) as output
    TCCR2A = 1<<COM2A0 | 0<<COM2B0 | 2<<WGM20; // Toggle OC2A on match
  } else error(PSTR("only pins 14 and 15 supported"), number(pin));
  int oct = octave + note/12;
  int prescaler = 9 - oct;
  if (prescaler<3 || prescaler>6) error(PSTR("octave out of range"), number(oct));
  OCR2A = pgm_read_byte(&scale[note%12]) - 1;
  TCCR2B = 0<<WGM22 | prescaler<<CS20;

#elif defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
  int oct = octave + note/12;
  int prescaler = 8 - oct;
  if (prescaler<0 || prescaler>8) error(PSTR("octave out of range"), number(oct));
  tone(pin, scale[note%12]>>prescaler);

#elif defined(CPU_AVR128DX48)
  int oct = octave + note/12;
  int prescaler = 8 - oct;
  if (prescaler<0 || prescaler>8) error(PSTR("octave out of range"), number(oct));
  tone(pin, pgm_read_word(&scale[note%12])>>prescaler);
#endif
}

void nonote (int pin) {
#if defined(CPU_ATmega4809) || defined(CPU_AVR128DX48) || defined(CPU_ATtiny3227)
  noTone(pin);
#else
  (void) pin;
  TCCR2B = 0<<WGM22 | 0<<CS20;
#endif
}

// Sleep

#if defined(CPU_ATmega328P) || defined(CPU_ATmega2560) || defined(CPU_ATmega1284P)
  // Interrupt vector for sleep watchdog
  ISR(WDT_vect) {
  WDTCSR |= 1<<WDIE;
}
#endif

void initsleep () {
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
}

void sleep () {
#if defined(CPU_ATtiny3227)
  ADC0.CTRLA = ADC0.CTRLA & ~1; // Turn off ADC
  delay(100);  // Give serial time to settle
  sleep_enable();
  sleep_cpu();
  ADC0.CTRLA = ADC0.CTRLA | 1; // Turn on ADC
#elif defined(CPU_ATmega328P) || defined(CPU_ATmega2560) || defined(CPU_ATmega1284P)
  ADCSRA = ADCSRA & ~(1<<ADEN); // Turn off ADC
  delay(100);  // Give serial time to settle
  sleep_enable();
  sleep_cpu();
  ADCSRA = ADCSRA | 1<<ADEN; // Turn on ADC
#endif
}

void doze (int secs) {
#if defined(CPU_ATmega328P) || defined(CPU_ATmega2560) || defined(CPU_ATmega1284P)
  // Set up Watchdog timer for 1 Hz interrupt
  WDTCSR = 1<<WDCE | 1<<WDE;
  WDTCSR = 1<<WDIE | 6<<WDP0;     // 1 sec interrupt
#if defined(CPU_ATmega2560) || defined(CPU_ATmega1284P)
  PRR0 = PRR0 | 1<<PRTIM0;
#endif
  while (secs > 0) { sleep(); secs--; }
  WDTCSR = 1<<WDCE | 1<<WDE;     // Disable watchdog
  WDTCSR = 0;
#if defined(CPU_ATmega2560) || defined(CPU_ATmega1284P)
  PRR0 = PRR0 & ~(1<<PRTIM0);
#endif
#else
  delay(1000*secs);
#endif
}

// Prettyprint

const int PPINDENT = 2;
const int PPWIDTH = 80;

void pcount (char c) {
  if (c == '\n') PrintCount++;
  PrintCount++;
}

uint8_t atomwidth (object *obj) {
  PrintCount = 0;
  printobject(obj, pcount);
  return PrintCount;
}

uint8_t basewidth (object *obj, uint8_t base) {
  PrintCount = 0;
  pintbase(obj->integer, base, pcount);
  return PrintCount;
}

bool quoted (object *obj) {
  return (consp(obj) && car(obj) != NULL && car(obj)->name == sym(QUOTE) && consp(cdr(obj)) && cddr(obj) == NULL);
}

int subwidth (object *obj, int w) {
  if (atom(obj)) return w - atomwidth(obj);
  if (quoted(obj)) obj = car(cdr(obj));
  return subwidthlist(obj, w - 1);
}

int subwidthlist (object *form, int w) {
  while (form != NULL && w >= 0) {
    if (atom(form)) return w - (2 + atomwidth(form));
    w = subwidth(car(form), w - 1);
    form = cdr(form);
  }
  return w;
}

void superprint (object *form, int lm, pfun_t pfun) {
  if (atom(form)) {
    if (symbolp(form) && form->name == sym(NOTHING)) printsymbol(form, pfun);
    else printobject(form, pfun);
  } else if (quoted(form)) {
    pfun('\'');
    superprint(car(cdr(form)), lm + 1, pfun);
  } else {
    lm = lm + PPINDENT;
    bool fits = (subwidth(form, PPWIDTH - lm - PPINDENT) >= 0);
    int special = 0, extra = 0; bool separate = true;
    object *arg = car(form);
    if (symbolp(arg) && builtinp(arg->name)) {
      uint8_t minmax = getminmax(builtin(arg->name));
      if (minmax == 0327 || minmax == 0313) special = 2; // defun, setq, setf, defvar
      else if (minmax == 0317 || minmax == 0017 || minmax == 0117 || minmax == 0123) special = 1;
    }
    while (form != NULL) {
      if (atom(form)) { pfstring(PSTR(" . "), pfun); printobject(form, pfun); pfun(')'); return; }
      else if (separate) { 
        pfun('(');
        separate = false;
      } else if (special) {
        pfun(' ');
        special--; 
      } else if (fits) {
        pfun(' ');
      } else { pln(pfun); indent(lm, ' ', pfun); }
      superprint(car(form), lm+extra, pfun);
      form = cdr(form);
    }
    pfun(')');
  }
}

object *edit (object *fun) {
  while (1) {
    if (tstflag(EXITEDITOR)) return fun;
    char c = gserial();
    if (c == 'q') setflag(EXITEDITOR);
    else if (c == 'b') return fun;
    else if (c == 'r') fun = read(gserial);
    else if (c == '\n') { pfl(pserial); superprint(fun, 0, pserial); pln(pserial); }
    else if (c == 'c') fun = cons(read(gserial), fun);
    else if (atom(fun)) pserial('!');
    else if (c == 'd') fun = cons(car(fun), edit(cdr(fun)));
    else if (c == 'a') fun = cons(edit(car(fun)), cdr(fun));
    else if (c == 'x') fun = cdr(fun);
    else pserial('?');
  }
}

// Special forms

object *sp_quote (object *args, object *env) {
  (void) env;
  return first(args);
}

object *sp_or (object *args, object *env) {
  while (args != NULL) {
    object *val = eval(car(args), env);
    if (val != NULL) return val;
    args = cdr(args);
  }
  return nil;
}

object *sp_defun (object *args, object *env) {
  (void) env;
  object *var = first(args);
  if (!symbolp(var)) error(notasymbol, var);
  object *val = cons(bsymbol(LAMBDA), cdr(args));
  object *pair = value(var->name, GlobalEnv);
  if (pair != NULL) cdr(pair) = val;
  else push(cons(var, val), GlobalEnv);
  return var;
}

object *sp_defvar (object *args, object *env) {
  object *var = first(args);
  if (!symbolp(var)) error(notasymbol, var);
  object *val = NULL;
  args = cdr(args);
  if (args != NULL) { setflag(NOESC); val = eval(first(args), env); clrflag(NOESC); }
  object *pair = value(var->name, GlobalEnv);
  if (pair != NULL) cdr(pair) = val;
  else push(cons(var, val), GlobalEnv);
  return var;
}

object *sp_setq (object *args, object *env) {
  object *arg = nil;
  while (args != NULL) {
    if (cdr(args) == NULL) error2(oddargs);
    object *pair = findvalue(first(args), env);
    arg = eval(second(args), env);
    cdr(pair) = arg;
    args = cddr(args);
  }
  return arg;
}

object *sp_loop (object *args, object *env) {
  object *start = args;
  for (;;) {
    args = start;
    while (args != NULL) {
      object *result = eval(car(args),env);
      if (tstflag(RETURNFLAG)) {
        clrflag(RETURNFLAG);
        return result;
      }
      args = cdr(args);
    }
    testescape();
  }
}

object *sp_push (object *args, object *env) {
  int bit;
  object *item = eval(first(args), env);
  object **loc = place(second(args), env, &bit);
  if (bit != -1) error2(invalidarg);
  push(item, *loc);
  return *loc;
}

object *sp_pop (object *args, object *env) {
  int bit;
  object *arg = first(args);
  if (arg == NULL) error2(invalidarg);
  object **loc = place(arg, env, &bit);
  if (bit < -1) error(invalidarg, arg);
  if (!consp(*loc)) error(notalist, *loc);
  object *result = car(*loc);
  pop(*loc);
  return result;
}

// Accessors

object *sp_incf (object *args, object *env) {
  return incfdecf(args, 1, env);
}

object *sp_decf (object *args, object *env) {
  return incfdecf(args, -1, env);
}

object *sp_setf (object *args, object *env) {
  int bit;
  object *arg = nil;
  while (args != NULL) {
    if (cdr(args) == NULL) error2(oddargs);
    object **loc = place(first(args), env, &bit);
    arg = eval(second(args), env);
    *loc = arg;
    args = cddr(args);
  }
  return arg;
}

// Other special forms

object *sp_dolist (object *args, object *env) {
  object *params = checkarguments(args, 2, 3);
  object *var = first(params);
  object *list = eval(second(params), env);
  protect(list); // Don't GC the list
  object *pair = cons(var,nil);
  push(pair,env);
  params = cddr(params);
  args = cdr(args);
  while (list != NULL) {
    if (improperp(list)) error(notproper, list);
    cdr(pair) = first(list);
    object *forms = args;
    while (forms != NULL) {
      object *result = eval(car(forms), env);
      if (tstflag(RETURNFLAG)) {
        clrflag(RETURNFLAG);
        unprotect();
        return result;
      }
      forms = cdr(forms);
    }
    list = cdr(list);
  }
  cdr(pair) = nil;
  unprotect();
  if (params == NULL) return nil;
  return eval(car(params), env);
}

object *sp_dotimes (object *args, object *env) {
  object *params = checkarguments(args, 2, 3);
  object *var = first(params);
  int count = checkinteger(eval(second(params), env));
  int index = 0;
  params = cddr(params);
  object *pair = cons(var,number(0));
  push(pair,env);
  args = cdr(args);
  while (index < count) {
    cdr(pair) = number(index);
    object *forms = args;
    while (forms != NULL) {
      object *result = eval(car(forms), env);
      if (tstflag(RETURNFLAG)) {
        clrflag(RETURNFLAG);
        return result;
      }
      forms = cdr(forms);
    }
    index++;
  }
  cdr(pair) = number(index);
  if (params == NULL) return nil;
  return eval(car(params), env);
}

object *sp_trace (object *args, object *env) {
  (void) env;
  while (args != NULL) {
    object *var = first(args);
    if (!symbolp(var)) error(notasymbol, var);
    trace(var->name);
    args = cdr(args);
  }
  int i = 0;
  while (i < TRACEMAX) {
    if (TraceFn[i] != 0) args = cons(symbol(TraceFn[i]), args);
    i++;
  }
  return args;
}

object *sp_untrace (object *args, object *env) {
  (void) env;
  if (args == NULL) {
    int i = 0;
    while (i < TRACEMAX) {
      if (TraceFn[i] != 0) args = cons(symbol(TraceFn[i]), args);
      TraceFn[i] = 0;
      i++;
    }
  } else {
    while (args != NULL) {
      object *var = first(args);
      if (!symbolp(var)) error(notasymbol, var);
      untrace(var->name);
      args = cdr(args);
    }
  }
  return args;
}

object *sp_formillis (object *args, object *env) {
  object *param = checkarguments(args, 0, 1);
  unsigned long start = millis();
  unsigned long now, total = 0;
  if (param != NULL) total = checkinteger(eval(first(param), env));
  eval(tf_progn(cdr(args),env), env);
  do {
    now = millis() - start;
    testescape();
  } while (now < total);
  if (now <= INT_MAX) return number(now);
  return nil;
}

object *sp_time (object *args, object *env) {
  unsigned long start = millis();
  object *result = eval(first(args), env);
  unsigned long elapsed = millis() - start;
  printobject(result, pserial);
  pfstring(PSTR("\nTime: "), pserial);
  if (elapsed < 1000) {
    pint(elapsed, pserial);
    pfstring(PSTR(" ms\n"), pserial);
  } else {
    elapsed = elapsed+50;
    pint(elapsed/1000, pserial);
    pserial('.'); pint((elapsed/100)%10, pserial);
    pfstring(PSTR(" s\n"), pserial);
  }
  return bsymbol(NOTHING);
}

object *sp_withoutputtostring (object *args, object *env) {
  object *params = checkarguments(args, 1, 1);
  object *var = first(params);
  object *pair = cons(var, stream(STRINGSTREAM, 0));
  push(pair,env);
  object *string = startstring();
  protect(string);
  object *forms = cdr(args);
  eval(tf_progn(forms,env), env);
  unprotect();
  return string;
}

object *sp_withserial (object *args, object *env) {
  object *params = checkarguments(args, 2, 3);
  object *var = first(params);
  int address = checkinteger(eval(second(params), env));
  params = cddr(params);
  int baud = 96;
  if (params != NULL) baud = checkinteger(eval(first(params), env));
  object *pair = cons(var, stream(SERIALSTREAM, address));
  push(pair,env);
  serialbegin(address, baud);
  object *forms = cdr(args);
  object *result = eval(tf_progn(forms,env), env);
  serialend(address);
  return result;
}

object *sp_withi2c (object *args, object *env) {
  object *params = checkarguments(args, 2, 4);
  object *var = first(params);
  int address = checkinteger(eval(second(params), env));
  params = cddr(params);
  if (address == 0 && params != NULL) params = cdr(params); // Ignore port
  int read = 0; // Write
  I2Ccount = 0;
  if (params != NULL) {
    object *rw = eval(first(params), env);
    if (integerp(rw)) I2Ccount = rw->integer;
    read = (rw != NULL);
  }
  I2Cinit(1); // Pullups
  object *pair = cons(var, (I2Cstart(address, read)) ? stream(I2CSTREAM, address) : nil);
  push(pair,env);
  object *forms = cdr(args);
  object *result = eval(tf_progn(forms,env), env);
  I2Cstop(read);
  return result;
}

object *sp_withspi (object *args, object *env) {
  object *params = checkarguments(args, 2, 6);
  object *var = first(params);
  params = cdr(params);
  if (params == NULL) error2(nostream);
  int pin = checkinteger(eval(car(params), env));
  pinMode(pin, OUTPUT);
  digitalWrite(pin, HIGH);
  params = cdr(params);
  int clock = 4000, mode = SPI_MODE0; // Defaults
  int bitorder = MSBFIRST;
  if (params != NULL) {
    clock = checkinteger(eval(car(params), env));
    params = cdr(params);
    if (params != NULL) {
      bitorder = (checkinteger(eval(car(params), env)) == 0) ? LSBFIRST : MSBFIRST;
      params = cdr(params);
      if (params != NULL) {
        int modeval = checkinteger(eval(car(params), env));
        mode = (modeval == 3) ? SPI_MODE3 : (modeval == 2) ? SPI_MODE2 : (modeval == 1) ? SPI_MODE1 : SPI_MODE0;
      }
    }
  }
  object *pair = cons(var, stream(SPISTREAM, pin));
  push(pair,env);
  SPI.begin();
  SPI.beginTransaction(SPISettings(((unsigned long)clock * 1000), bitorder, mode));
  digitalWrite(pin, LOW);
  object *forms = cdr(args);
  object *result = eval(tf_progn(forms,env), env);
  digitalWrite(pin, HIGH);
  SPI.endTransaction();
  return result;
}

object *sp_withsdcard (object *args, object *env) {
  #if defined(sdcardsupport)
  object *params = checkarguments(args, 2, 3);
  object *var = first(params);
  params = cdr(params);
  if (params == NULL) error2(PSTR("no filename specified"));
  builtin_t temp = Context;
  object *filename = eval(first(params), env);
  Context = temp;
  if (!stringp(filename)) error(PSTR("filename is not a string"), filename);
  params = cdr(params);
  SD.begin(SDCARD_SS_PIN);
  int mode = 0;
  if (params != NULL && first(params) != NULL) mode = checkinteger(first(params));
  int oflag = O_READ;
  if (mode == 1) oflag = O_RDWR | O_CREAT | O_APPEND; else if (mode == 2) oflag = O_RDWR | O_CREAT | O_TRUNC;
  if (mode >= 1) {
    char buffer[BUFFERSIZE];
    SDpfile = SD.open(MakeFilename(filename, buffer), oflag);
    if (!SDpfile) error2(PSTR("problem writing to SD card or invalid filename"));
  } else {
    char buffer[BUFFERSIZE];
    SDgfile = SD.open(MakeFilename(filename, buffer), oflag);
    if (!SDgfile) error2(PSTR("problem reading from SD card or invalid filename"));
  }
  object *pair = cons(var, stream(SDSTREAM, 1));
  push(pair,env);
  object *forms = cdr(args);
  object *result = eval(tf_progn(forms,env), env);
  if (mode >= 1) SDpfile.close(); else SDgfile.close();
  return result;
  #else
  (void) args, (void) env;
  error2(PSTR("not supported"));
  return nil;
  #endif
}

// Tail-recursive forms

object *tf_progn (object *args, object *env) {
  if (args == NULL) return nil;
  object *more = cdr(args);
  while (more != NULL) {
    object *result = eval(car(args),env);
    if (tstflag(RETURNFLAG)) return quote(result);
    args = more;
    more = cdr(args);
  }
  return car(args);
}

object *tf_if (object *args, object *env) {
  if (args == NULL || cdr(args) == NULL) error2(toofewargs);
  if (eval(first(args), env) != nil) return second(args);
  args = cddr(args);
  return (args != NULL) ? first(args) : nil;
}

object *tf_cond (object *args, object *env) {
  while (args != NULL) {
    object *clause = first(args);
    if (!consp(clause)) error(illegalclause, clause);
    object *test = eval(first(clause), env);
    object *forms = cdr(clause);
    if (test != nil) {
      if (forms == NULL) return quote(test); else return tf_progn(forms, env);
    }
    args = cdr(args);
  }
  return nil;
}

object *tf_when (object *args, object *env) {
  if (args == NULL) error2(noargument);
  if (eval(first(args), env) != nil) return tf_progn(cdr(args),env);
  else return nil;
}

object *tf_unless (object *args, object *env) {
  if (args == NULL) error2(noargument);
  if (eval(first(args), env) != nil) return nil;
  else return tf_progn(cdr(args),env);
}

object *tf_case (object *args, object *env) {
  object *test = eval(first(args), env);
  args = cdr(args);
  while (args != NULL) {
    object *clause = first(args);
    if (!consp(clause)) error(illegalclause, clause);
    object *key = car(clause);
    object *forms = cdr(clause);
    if (consp(key)) {
      while (key != NULL) {
        if (eq(test,car(key))) return tf_progn(forms, env);
        key = cdr(key);
      }
    } else if (eq(test,key) || eq(key,tee)) return tf_progn(forms, env);
    args = cdr(args);
  }
  return nil;
}

object *tf_and (object *args, object *env) {
  if (args == NULL) return tee;
  object *more = cdr(args);
  while (more != NULL) {
    if (eval(car(args), env) == NULL) return nil;
    args = more;
    more = cdr(args);
  }
  return car(args);
}

// Core functions

object *fn_not (object *args, object *env) {
  (void) env;
  return (first(args) == nil) ? tee : nil;
}

object *fn_cons (object *args, object *env) {
  (void) env;
  return cons(first(args), second(args));
}

object *fn_atom (object *args, object *env) {
  (void) env;
  return atom(first(args)) ? tee : nil;
}

object *fn_listp (object *args, object *env) {
  (void) env;
  return listp(first(args)) ? tee : nil;
}

object *fn_consp (object *args, object *env) {
  (void) env;
  return consp(first(args)) ? tee : nil;
}

object *fn_symbolp (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  return (arg == NULL || symbolp(arg)) ? tee : nil;
}

object *fn_boundp (object *args, object *env) {
  return boundp(first(args), env) ? tee : nil;
}

object *fn_keywordp (object *args, object *env) {
  (void) env;
  return keywordp(first(args)) ? tee : nil;
}

object *fn_streamp (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  return streamp(arg) ? tee : nil;
}

object *fn_eq (object *args, object *env) {
  (void) env;
  return eq(first(args), second(args)) ? tee : nil;
}

object *fn_equal (object *args, object *env) {
  (void) env;
  return equal(first(args), second(args)) ? tee : nil;
}

// List functions

object *fn_car (object *args, object *env) {
  (void) env;
  return carx(first(args));
}

object *fn_cdr (object *args, object *env) {
  (void) env;
  return cdrx(first(args));
}

object *fn_caar (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b100);
}

object *fn_cadr (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b101);
}

object *fn_cdar (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b110);
}

object *fn_cddr (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b111);
}

object *fn_caaar (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b1000);
}

object *fn_caadr (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b1001);;
}

object *fn_cadar (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b1010);
}

object *fn_caddr (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b1011);
}

object *fn_cdaar (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b1100);
}

object *fn_cdadr (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b1101);
}

object *fn_cddar (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b1110);
}

object *fn_cdddr (object *args, object *env) {
  (void) env;
  return cxxxr(args, 0b1111);
}

object *fn_length (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  if (listp(arg)) return number(listlength(arg));
  if (!stringp(arg)) error(invalidarg, arg);
  return number(stringlength(arg));
}

object *fn_list (object *args, object *env) {
  (void) env;
  return args;
}

object *fn_reverse (object *args, object *env) {
  (void) env;
  object *list = first(args);
  object *result = NULL;
  while (list != NULL) {
    if (improperp(list)) error(notproper, list);
    push(first(list),result);
    list = cdr(list);
  }
  return result;
}

object *fn_nth (object *args, object *env) {
  (void) env;
  int n = checkinteger(first(args));
  if (n < 0) error(indexnegative, first(args));
  object *list = second(args);
  while (list != NULL) {
    if (improperp(list)) error(notproper, list);
    if (n == 0) return car(list);
    list = cdr(list);
    n--;
  }
  return nil;
}

object *fn_assoc (object *args, object *env) {
  (void) env;
  object *key = first(args);
  object *list = second(args);
  while (list != NULL) {
    if (improperp(list)) error(notproper, list);
    object *pair = first(list);
    if (!listp(pair)) error(PSTR("element is not a list"), pair);
    if (pair != NULL && eq(key,car(pair))) return pair;
    list = cdr(list);
  }
  return nil;
}

object *fn_member (object *args, object *env) {
  (void) env;
  object *item = first(args);
  object *list = second(args);
  while (list != NULL) {
    if (improperp(list)) error(notproper, list);
    if (eq(item,car(list))) return list;
    list = cdr(list);
  }
  return nil;
}

object *fn_apply (object *args, object *env) {
  object *previous = NULL;
  object *last = args;
  while (cdr(last) != NULL) {
    previous = last;
    last = cdr(last);
  }
  object *arg = car(last);
  if (!listp(arg)) error(notalist, arg);
  cdr(previous) = arg;
  return apply(first(args), cdr(args), env);
}

object *fn_funcall (object *args, object *env) {
  return apply(first(args), cdr(args), env);
}

object *fn_append (object *args, object *env) {
  (void) env;
  object *head = NULL;
  object *tail;
  while (args != NULL) {
    object *list = first(args);
    if (!listp(list)) error(notalist, list);
    while (consp(list)) {
      object *obj = cons(car(list), cdr(list));
      if (head == NULL) head = obj;
      else cdr(tail) = obj;
      tail = obj;
      list = cdr(list);
      if (cdr(args) != NULL && improperp(list)) error(notproper, first(args));
    }
    args = cdr(args);
  }
  return head;
}

object *fn_mapc (object *args, object *env) {
  return mapcl(args, env, false);
}

object *fn_mapcar (object *args, object *env) {
  return mapcarcan(args, env, mapcarfun, false);
}

object *fn_mapcan (object *args, object *env) {
  return mapcarcan(args, env, mapcanfun, false);
}

// Arithmetic functions

object *fn_add (object *args, object *env) {
  (void) env;
  int result = 0;
  while (args != NULL) {
    int temp = checkinteger(car(args));
    #if defined(checkoverflow)
    if (temp < 1) { if (INT_MIN - temp > result) error2(overflow); }
    else { if (INT_MAX - temp < result) error2(overflow); }
    #endif
    result = result + temp;
    args = cdr(args);
  }
  return number(result);
}

object *fn_subtract (object *args, object *env) {
  (void) env;
  int result = checkinteger(car(args));
  args = cdr(args);
  if (args == NULL) {
    #if defined(checkoverflow)
    if (result == INT_MIN) error2(overflow);
    #endif
    return number(-result);
  }
  while (args != NULL) {
    int temp = checkinteger(car(args));
    #if defined(checkoverflow)
    if (temp < 1) { if (INT_MAX + temp < result) error2(overflow); }
    else { if (INT_MIN + temp > result) error2(overflow); }
    #endif
    result = result - temp;
    args = cdr(args);
  }
  return number(result);
}

object *fn_multiply (object *args, object *env) {
  (void) env;
  int result = 1;
  while (args != NULL){
    #if defined(checkoverflow)
    signed long temp = (signed long) result * checkinteger(car(args));
    if ((temp > INT_MAX) || (temp < INT_MIN)) error2(overflow);
    result = temp;
    #else
    result = result * checkinteger(car(args));
    #endif
    args = cdr(args);
  }
  return number(result);
}

object *fn_divide (object *args, object *env) {
  (void) env;
  int result = checkinteger(first(args));
  args = cdr(args);
  while (args != NULL) {
    int arg = checkinteger(car(args));
    if (arg == 0) error2(divisionbyzero);
    #if defined(checkoverflow)
    if ((result == INT_MIN) && (arg == -1)) error2(overflow);
    #endif
    result = result / arg;
    args = cdr(args);
  }
  return number(result);
}

object *fn_mod (object *args, object *env) {
  (void) env;
  int arg1 = checkinteger(first(args));
  int arg2 = checkinteger(second(args));
  if (arg2 == 0) error2(divisionbyzero);
  int r = arg1 % arg2;
  if ((arg1<0) != (arg2<0)) r = r + arg2;
  return number(r);
}

object *fn_oneplus (object *args, object *env) {
  (void) env;
  int result = checkinteger(first(args));
  #if defined(checkoverflow)
  if (result == INT_MAX) error2(overflow);
  #endif
  return number(result + 1);
}

object *fn_oneminus (object *args, object *env) {
  (void) env;
  int result = checkinteger(first(args));
  #if defined(checkoverflow)
  if (result == INT_MIN) error2(overflow);
  #endif
  return number(result - 1);
}

object *fn_abs (object *args, object *env) {
  (void) env;
  int result = checkinteger(first(args));
  #if defined(checkoverflow)
  if (result == INT_MIN) error2(overflow);
  #endif
  return number(abs(result));
}

object *fn_random (object *args, object *env) {
  (void) env;
  int arg = checkinteger(first(args));
  return number(pseudoRandom(arg));
}

object *fn_maxfn (object *args, object *env) {
  (void) env;
  int result = checkinteger(first(args));
  args = cdr(args);
  while (args != NULL) {
    int next = checkinteger(car(args));
    if (next > result) result = next;
    args = cdr(args);
  }
  return number(result);
}

object *fn_minfn (object *args, object *env) {
  (void) env;
  int result = checkinteger(first(args));
  args = cdr(args);
  while (args != NULL) {
    int next = checkinteger(car(args));
    if (next < result) result = next;
    args = cdr(args);
  }
  return number(result);
}

// Arithmetic comparisons

object *fn_noteq (object *args, object *env) {
  (void) env;
  while (args != NULL) {   
    object *nargs = args;
    int arg1 = checkinteger(first(nargs));
    nargs = cdr(nargs);
    while (nargs != NULL) {
       int arg2 = checkinteger(first(nargs));
       if (arg1 == arg2) return nil;
       nargs = cdr(nargs);
    }
    args = cdr(args);
  }
  return tee;
}

object *fn_numeq (object *args, object *env) {
  (void) env;
  return compare(args, false, false, true);
}

object *fn_less (object *args, object *env) {
  (void) env;
  return compare(args, true, false, false);
}

object *fn_lesseq (object *args, object *env) {
  (void) env;
  return compare(args, true, false, true);
}

object *fn_greater (object *args, object *env) {
  (void) env;
  return compare(args, false, true, false);
}

object *fn_greatereq (object *args, object *env) {
  (void) env;
  return compare(args, false, true, true);
}

object *fn_plusp (object *args, object *env) {
  (void) env;
  int arg = checkinteger(first(args));
  if (arg > 0) return tee;
  else return nil;
}

object *fn_minusp (object *args, object *env) {
  (void) env;
  int arg = checkinteger(first(args));
  if (arg < 0) return tee;
  else return nil;
}

object *fn_zerop (object *args, object *env) {
  (void) env;
  int arg = checkinteger(first(args));
  return (arg == 0) ? tee : nil;
}

object *fn_oddp (object *args, object *env) {
  (void) env;
  int arg = checkinteger(first(args));
  return ((arg & 1) == 1) ? tee : nil;
}

object *fn_evenp (object *args, object *env) {
  (void) env;
  int arg = checkinteger(first(args));
  return ((arg & 1) == 0) ? tee : nil;
}

// Number functions

object *fn_integerp (object *args, object *env) {
  (void) env;
  return integerp(first(args)) ? tee : nil;
}

// Characters

object *fn_char (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  if (!stringp(arg)) error(notastring, arg);
  object *n = second(args);
  char c = nthchar(arg, checkinteger(n));
  if (c == 0) error(indexrange, n);
  return character(c);
}

object *fn_charcode (object *args, object *env) {
  (void) env;
  return number(checkchar(first(args)));
}

object *fn_codechar (object *args, object *env) {
  (void) env;
  return character(checkinteger(first(args)));
}

object *fn_characterp (object *args, object *env) {
  (void) env;
  return characterp(first(args)) ? tee : nil;
}

// Strings

object *fn_stringp (object *args, object *env) {
  (void) env;
  return stringp(first(args)) ? tee : nil;
}

object *fn_stringeq (object *args, object *env) {
  (void) env;
  return stringcompare(args, false, false, true) ? tee : nil;
}

object *fn_stringless (object *args, object *env) {
  (void) env;
  return stringcompare(args, true, false, false) ? tee : nil;
}

object *fn_stringgreater (object *args, object *env) {
  (void) env;
  return stringcompare(args, false, true, false) ? tee : nil;
}

object *fn_sort (object *args, object *env) {
  if (first(args) == NULL) return nil;
  object *list = cons(nil,first(args));
  protect(list);
  object *predicate = second(args);
  object *compare = cons(NULL, cons(NULL, NULL));
  protect(compare);
  object *ptr = cdr(list);
  while (cdr(ptr) != NULL) {
    object *go = list;
    while (go != ptr) {
      car(compare) = car(cdr(ptr));
      car(cdr(compare)) = car(cdr(go));
      if (apply(predicate, compare, env)) break;
      go = cdr(go);
    }
    if (go != ptr) {
      object *obj = cdr(ptr);
      cdr(ptr) = cdr(obj);
      cdr(obj) = cdr(go);
      cdr(go) = obj;
    } else ptr = cdr(ptr);
  }
  unprotect(); unprotect();
  return cdr(list);
}

object *fn_stringfn (object *args, object *env) {
  return fn_princtostring(args, env);
}

object *fn_concatenate (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  if (builtin(arg->name) != STRINGFN) error2(PSTR("only supports strings"));
  args = cdr(args);
  object *result = newstring();
  object *tail = result;
  while (args != NULL) {
    object *obj = checkstring(first(args));
    obj = cdr(obj);
    while (obj != NULL) {
      int quad = obj->chars;
      while (quad != 0) {
         char ch = quad>>((sizeof(int)-1)*8) & 0xFF;
         buildstring(ch, &tail);
         quad = quad<<8;
      }
      obj = car(obj);
    }
    args = cdr(args);
  }
  return result;
}

object *fn_subseq (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  int start = checkinteger(second(args)), end;
  if (start < 0) error(indexnegative, second(args));
  args = cddr(args);
  if (listp(arg)) {
    int length = listlength(arg);
    if (args != NULL) end = checkinteger(car(args)); else end = length;
    if (start > end || end > length) error2(indexrange);
    object *result = cons(NULL, NULL);
    object *ptr = result;
    for (int x = 0; x < end; x++) {
      if (x >= start) { cdr(ptr) = cons(car(arg), NULL); ptr = cdr(ptr); }
      arg = cdr(arg);
    }
    return cdr(result);
  } else if (stringp(arg)) {
    int length = stringlength(arg);
    if (args != NULL) end = checkinteger(car(args)); else end = length;
    if (start > end || end > length) error2(indexrange);
    object *result = newstring();
    object *tail = result;
    for (int i=start; i<end; i++) {
      char ch = nthchar(arg, i);
      buildstring(ch, &tail);
    }
    return result;
  } else error2(PSTR("argument is not a list or string"));
  return nil;
}

object *fn_readfromstring (object *args, object *env) {
  (void) env;
  object *arg = checkstring(first(args));
  GlobalString = arg;
  GlobalStringIndex = 0;
  object *val = read(gstr);
  LastChar = 0;
  return val;
}

object *fn_princtostring (object *args, object *env) {
  (void) env;
  return princtostring(first(args));
}

object *fn_prin1tostring (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  object *obj = startstring();
  printobject(arg, pstr);
  return obj;
}

// Bitwise operators

object *fn_logand (object *args, object *env) {
  (void) env;
  int result = -1;
  while (args != NULL) {
    result = result & checkinteger(first(args));
    args = cdr(args);
  }
  return number(result);
}

object *fn_logior (object *args, object *env) {
  (void) env;
  int result = 0;
  while (args != NULL) {
    result = result | checkinteger(first(args));
    args = cdr(args);
  }
  return number(result);
}

object *fn_logxor (object *args, object *env) {
  (void) env;
  int result = 0;
  while (args != NULL) {
    result = result ^ checkinteger(first(args));
    args = cdr(args);
  }
  return number(result);
}

object *fn_lognot (object *args, object *env) {
  (void) env;
  int result = checkinteger(car(args));
  return number(~result);
}

object *fn_ash (object *args, object *env) {
  (void) env;
  int value = checkinteger(first(args));
  int count = checkinteger(second(args));
  if (count >= 0) return number(value << count);
  else return number(value >> abs(count));
}

object *fn_logbitp (object *args, object *env) {
  (void) env;
  int index = checkinteger(first(args));
  int value = checkinteger(second(args));
  return (bitRead(value, index) == 1) ? tee : nil;
}

// System functions

object *fn_eval (object *args, object *env) {
  return eval(first(args), env);
}

object *fn_return (object *args, object *env) {
  (void) env;
  setflag(RETURNFLAG);
  if (args == NULL) return nil; else return first(args);
}

object *fn_globals (object *args, object *env) {
  (void) args, (void) env;
  object *result = cons(NULL, NULL);
  object *ptr = result;
  object *arg = GlobalEnv;
  while (arg != NULL) {
    cdr(ptr) = cons(car(car(arg)), NULL); ptr = cdr(ptr);
    arg = cdr(arg);
  }
  return cdr(result);
}

object *fn_locals (object *args, object *env) {
  (void) args;
  return env;
}

object *fn_makunbound (object *args, object *env) {
  (void) env;
  object *var = first(args);
  if (!symbolp(var)) error(notasymbol, var);
  delassoc(var, &GlobalEnv);
  return var;
}

object *fn_break (object *args, object *env) {
  (void) args;
  pfstring(PSTR("\nBreak!\n"), pserial);
  BreakLevel++;
  repl(env);
  BreakLevel--;
  return nil;
}

object *fn_read (object *args, object *env) {
  (void) env;
  gfun_t gfun = gstreamfun(args);
  return read(gfun);
}

object *fn_prin1 (object *args, object *env) {
  (void) env;
  object *obj = first(args);
  pfun_t pfun = pstreamfun(cdr(args));
  printobject(obj, pfun);
  return obj;
}

object *fn_print (object *args, object *env) {
  (void) env;
  object *obj = first(args);
  pfun_t pfun = pstreamfun(cdr(args));
  pln(pfun);
  printobject(obj, pfun);
  pfun(' ');
  return obj;
}

object *fn_princ (object *args, object *env) {
  (void) env;
  object *obj = first(args);
  pfun_t pfun = pstreamfun(cdr(args));
  prin1object(obj, pfun);
  return obj;
}

object *fn_terpri (object *args, object *env) {
  (void) env;
  pfun_t pfun = pstreamfun(args);
  pln(pfun);
  return nil;
}

object *fn_readbyte (object *args, object *env) {
  (void) env;
  gfun_t gfun = gstreamfun(args);
  int c = gfun();
  return (c == -1) ? nil : number(c);
}

object *fn_readline (object *args, object *env) {
  (void) env;
  gfun_t gfun = gstreamfun(args);
  return readstring('\n', false, gfun);
}

object *fn_writebyte (object *args, object *env) {
  (void) env;
  int value = checkinteger(first(args));
  pfun_t pfun = pstreamfun(cdr(args));
  (pfun)(value);
  return nil;
}

object *fn_writestring (object *args, object *env) {
  (void) env;
  object *obj = first(args);
  pfun_t pfun = pstreamfun(cdr(args));
  char temp = Flags;
  clrflag(PRINTREADABLY);
  printstring(obj, pfun);
  Flags = temp;
  return nil;
}

object *fn_writeline (object *args, object *env) {
  (void) env;
  object *obj = first(args);
  pfun_t pfun = pstreamfun(cdr(args));
  char temp = Flags;
  clrflag(PRINTREADABLY);
  printstring(obj, pfun);
  pln(pfun);
  Flags = temp;
  return nil;
}

object *fn_restarti2c (object *args, object *env) {
  (void) env;
  int stream = isstream(first(args));
  args = cdr(args);
  int read = 0; // Write
  I2Ccount = 0;
  if (args != NULL) {
    object *rw = first(args);
    if (integerp(rw)) I2Ccount = rw->integer;
    read = (rw != NULL);
  }
  int address = stream & 0xFF;
  if (stream>>8 != I2CSTREAM) error2(PSTR("not an i2c stream"));
  return I2Crestart(address, read) ? tee : nil;
}

object *fn_gc (object *obj, object *env) {
  int initial = Freespace;
  unsigned long start = micros();
  gc(obj, env);
  unsigned long elapsed = micros() - start;
  pfstring(PSTR("Space: "), pserial);
  pint(Freespace - initial, pserial);
  pfstring(PSTR(" bytes, Time: "), pserial);
  pint(elapsed, pserial);
  pfstring(PSTR(" us\n"), pserial);
  return nil;
}

object *fn_room (object *args, object *env) {
  (void) args, (void) env;
  return number(Freespace);
}

object *fn_saveimage (object *args, object *env) {
  if (args != NULL) args = eval(first(args), env);
  return number(saveimage(args));
}

object *fn_loadimage (object *args, object *env) {
  (void) env;
  if (args != NULL) args = first(args);
  return number(loadimage(args));
}

object *fn_cls (object *args, object *env) {
  (void) args, (void) env;
  pserial(12);
  return nil;
}

// Arduino procedures

object *fn_pinmode (object *args, object *env) {
  (void) env; int pin;
  object *arg = first(args);
  if (keywordp(arg)) pin = checkkeyword(arg);
  else pin = checkinteger(first(args));
  int pm = INPUT;
  arg = second(args);
  if (keywordp(arg)) pm = checkkeyword(arg);
  else if (integerp(arg)) {
    int mode = arg->integer;
    if (mode == 1) pm = OUTPUT; else if (mode == 2) pm = INPUT_PULLUP;
    #if defined(INPUT_PULLDOWN)
    else if (mode == 4) pm = INPUT_PULLDOWN;
    #endif
  } else if (arg != nil) pm = OUTPUT;
  pinMode(pin, pm);
  return nil;
}

object *fn_digitalread (object *args, object *env) {
  (void) env;
  int pin;
  object *arg = first(args);
  if (keywordp(arg)) pin = checkkeyword(arg);
  else pin = checkinteger(arg);
  if (digitalRead(pin) != 0) return tee; else return nil;
}

object *fn_digitalwrite (object *args, object *env) {
  (void) env;
  int pin;
  object *arg = first(args);
  if (keywordp(arg)) pin = checkkeyword(arg);
  else pin = checkinteger(arg);
  arg = second(args);
  int mode;
  if (keywordp(arg)) mode = checkkeyword(arg);
  else if (integerp(arg)) mode = arg->integer ? HIGH : LOW;
  else mode = (arg != nil) ? HIGH : LOW;
  digitalWrite(pin, mode);
  return arg;
}

object *fn_analogread (object *args, object *env) {
  (void) env;
  int pin;
  object *arg = first(args);
  if (keywordp(arg)) pin = checkkeyword(arg);
  else {
    pin = checkinteger(arg);
    checkanalogread(pin);
  }
  return number(analogRead(pin));
}

object *fn_analogreference (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  analogReference(checkkeyword(arg));
  return arg;
}

object *fn_analogreadresolution (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  #if defined(CPU_AVR128DX48)
  uint8_t res = checkinteger(arg);
  if (res == 10) analogReadResolution(10);
  else if (res == 12) analogReadResolution(12);
  else error(PSTR("invalid resolution"), arg);
  #else
  error2(PSTR("not supported"));
  #endif
  return arg;
}

object *fn_analogwrite (object *args, object *env) {
  (void) env;
  int pin;
  object *arg = first(args);
  if (keywordp(arg)) pin = checkkeyword(arg);
  else pin = checkinteger(arg);
  checkanalogwrite(pin);
  object *value = second(args);
  analogWrite(pin, checkinteger(value));
  return value;
}

object *fn_dacreference (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  #if defined(CPU_AVR128DX48)
  int ref = checkinteger(arg);
  DACReference(ref);
  #endif
  return arg;
}

object *fn_delay (object *args, object *env) {
  (void) env;
  object *arg1 = first(args);
  unsigned long start = millis();
  unsigned long total = checkinteger(arg1);
  do testescape();
  while (millis() - start < total);
  return arg1;
}

object *fn_millis (object *args, object *env) {
  (void) args, (void) env;
  return number(millis());
}

object *fn_sleep (object *args, object *env) {
  (void) env;
  if (args == NULL || first(args) == NULL) { sleep(); return nil; }
  object *arg1 = first(args);
  doze(checkinteger(arg1));
  return arg1;
}

object *fn_note (object *args, object *env) {
  (void) env;
  static int pin = 255;
  if (args != NULL) {
    pin = checkinteger(first(args));
    int note = 48, octave = 0;
    if (cdr(args) != NULL) {
      note = checkinteger(second(args));
      if (cddr(args) != NULL) octave = checkinteger(third(args));
    }
    playnote(pin, note, octave);
  } else nonote(pin);
  return nil;
}

object *fn_register (object *args, object *env) {
  (void) env;
  object *arg = first(args);
  int addr;
  if (keywordp(arg)) addr = checkkeyword(arg);
  else addr = checkinteger(first(args));
  if (cdr(args) == NULL) return number(*(volatile uint8_t *)addr);
  (*(volatile uint8_t *)addr) = checkinteger(second(args));
  return second(args);
}

// Tree Editor

object *fn_edit (object *args, object *env) {
  object *fun = first(args);
  object *pair = findvalue(fun, env);
  clrflag(EXITEDITOR);
  object *arg = edit(eval(fun, env));
  cdr(pair) = arg;
  return arg;
}

// Pretty printer

object *fn_pprint (object *args, object *env) {
  (void) env;
  object *obj = first(args);
  pfun_t pfun = pstreamfun(cdr(args));
  pln(pfun);
  superprint(obj, 0, pfun);
  return bsymbol(NOTHING);
}

object *fn_pprintall (object *args, object *env) {
  (void) env;
  pfun_t pfun = pstreamfun(args);
  object *globals = GlobalEnv;
  while (globals != NULL) {
    object *pair = first(globals);
    object *var = car(pair);
    object *val = cdr(pair);
    pln(pfun);
    if (consp(val) && symbolp(car(val)) && builtin(car(val)->name) == LAMBDA) {
      superprint(cons(bsymbol(DEFUN), cons(var, cdr(val))), 0, pfun);
    #if defined(CODESIZE)
    } else if (consp(val) && car(val)->type == CODE) {
      superprint(cons(bsymbol(DEFCODE), cons(var, cdr(val))), 0, pfun);
    #endif
    } else {
      superprint(cons(bsymbol(DEFVAR), cons(var, cons(quote(val), NULL))), 0, pfun);
    }
    pln(pfun);
    testescape();
    globals = cdr(globals);
  }
  return bsymbol(NOTHING);
}

// Format

object *fn_format (object *args, object *env) {
  (void) env;
  pfun_t pfun = pserial;
  object *output = first(args);
  object *obj;
  if (output == nil) { obj = startstring(); pfun = pstr; }
  else if (output != tee) pfun = pstreamfun(args);
  object *formatstr = checkstring(second(args));
  object *save = NULL;
  args = cddr(args);
  int len = stringlength(formatstr);
  uint8_t n = 0, width = 0, w, bra = 0;
  char pad = ' ';
  bool tilde = false, mute = false, comma = false, quote = false;
  while (n < len) {
    char ch = nthchar(formatstr, n);
    char ch2 = ch & ~0x20; // force to upper case
    if (tilde) {
     if (ch == '}') {
        if (save == NULL) formaterr(formatstr, PSTR("no matching ~{"), n);
        if (args == NULL) { args = cdr(save); save = NULL; } else n = bra;
        mute = false; tilde = false;
      }
      else if (!mute) {
        if (comma && quote) { pad = ch; comma = false, quote = false; }
        else if (ch == '\'') {
          if (comma) quote = true;
          else formaterr(formatstr, PSTR("quote not valid"), n);
        }
        else if (ch == '~') { pfun('~'); tilde = false; }
        else if (ch >= '0' && ch <= '9') width = width*10 + ch - '0';
        else if (ch == ',') comma = true;
        else if (ch == '%') { pln(pfun); tilde = false; }
        else if (ch == '&') { pfl(pfun); tilde = false; }
        else if (ch == '^') {
          if (save != NULL && args == NULL) mute = true;
          tilde = false;
        }
        else if (ch == '{') {
          if (save != NULL) formaterr(formatstr, PSTR("can't nest ~{"), n);
          if (args == NULL) formaterr(formatstr, noargument, n);
          if (!listp(first(args))) formaterr(formatstr, notalist, n);
          save = args; args = first(args); bra = n; tilde = false;
          if (args == NULL) mute = true;
        }
        else if (ch2 == 'A' || ch2 == 'S' || ch2 == 'D' || ch2 == 'G' || ch2 == 'X' || ch2 == 'B') {
          if (args == NULL) formaterr(formatstr, noargument, n);
          object *arg = first(args); args = cdr(args);
          uint8_t aw = atomwidth(arg);
          if (width < aw) w = 0; else w = width-aw;
          tilde = false;
          if (ch2 == 'A') { prin1object(arg, pfun); indent(w, pad, pfun); }
          else if (ch2 == 'S') { printobject(arg, pfun); indent(w, pad, pfun); }
          else if (ch2 == 'D' || ch2 == 'G') { indent(w, pad, pfun); prin1object(arg, pfun); }
          else if (ch2 == 'X' || ch2 == 'B') {
            if (integerp(arg)) {
              uint8_t base = (ch2 == 'B') ? 2 : 16;
              uint8_t hw = basewidth(arg, base); if (width < hw) w = 0; else w = width-hw;
              indent(w, pad, pfun); pintbase(arg->integer, base, pfun);
            } else {
              indent(w, pad, pfun); prin1object(arg, pfun);
            }
          }
          tilde = false;
        } else formaterr(formatstr, PSTR("invalid directive"), n);
      }
    } else {
      if (ch == '~') { tilde = true; pad = ' '; width = 0; comma = false; quote = false; }
      else if (!mute) pfun(ch);
    }
    n++;
  }
  if (output == nil) return obj;
  else return nil;
}

// LispLibrary

object *fn_require (object *args, object *env) {
  object *arg = first(args);
  object *globals = GlobalEnv;
  if (!symbolp(arg)) error(notasymbol, arg);
  while (globals != NULL) {
    object *pair = first(globals);
    object *var = car(pair);
    if (symbolp(var) && var == arg) return nil;
    globals = cdr(globals);
  }
  GlobalStringIndex = 0;
  object *line = read(glibrary);
  while (line != NULL) {
    // Is this the definition we want
    symbol_t fname = first(line)->name;
    if ((fname == sym(DEFUN) || fname == sym(DEFVAR)) && symbolp(second(line)) && second(line)->name == arg->name) {
      eval(line, env);
      return tee;
    }
    line = read(glibrary);
  }
  return nil;
}

object *fn_listlibrary (object *args, object *env) {
  (void) args, (void) env;
  GlobalStringIndex = 0;
  object *line = read(glibrary);
  while (line != NULL) {
    builtin_t bname = builtin(first(line)->name);
    if (bname == DEFUN || bname == DEFVAR) {
      printsymbol(second(line), pserial); pserial(' ');
    }
    line = read(glibrary);
  }
  return bsymbol(NOTHING);
}

// Built-in symbol names
const char string0[] PROGMEM = "nil";
const char string1[] PROGMEM = "t";
const char string2[] PROGMEM = "nothing";
const char string3[] PROGMEM = "&optional";
const char string4[] PROGMEM = "&rest";
const char string5[] PROGMEM = "lambda";
const char string6[] PROGMEM = "let";
const char string7[] PROGMEM = "let*";
const char string8[] PROGMEM = "closure";
const char string9[] PROGMEM = "quote";
const char string10[] PROGMEM = "defun";
const char string11[] PROGMEM = "defvar";
const char string12[] PROGMEM = "eq";
const char string13[] PROGMEM = "car";
const char string14[] PROGMEM = "first";
const char string15[] PROGMEM = "cdr";
const char string16[] PROGMEM = "rest";
const char string17[] PROGMEM = "nth";
const char string18[] PROGMEM = "char";
const char string19[] PROGMEM = "string";
const char string20[] PROGMEM = "pinmode";
const char string21[] PROGMEM = "digitalwrite";
const char string22[] PROGMEM = "analogread";
const char string23[] PROGMEM = "analogreference";
const char string24[] PROGMEM = "register";
const char string25[] PROGMEM = "format";
const char string26[] PROGMEM = "or";
const char string27[] PROGMEM = "setq";
const char string28[] PROGMEM = "loop";
const char string29[] PROGMEM = "push";
const char string30[] PROGMEM = "pop";
const char string31[] PROGMEM = "incf";
const char string32[] PROGMEM = "decf";
const char string33[] PROGMEM = "setf";
const char string34[] PROGMEM = "dolist";
const char string35[] PROGMEM = "dotimes";
const char string36[] PROGMEM = "trace";
const char string37[] PROGMEM = "untrace";
const char string38[] PROGMEM = "for-millis";
const char string39[] PROGMEM = "time";
const char string40[] PROGMEM = "with-output-to-string";
const char string41[] PROGMEM = "with-serial";
const char string42[] PROGMEM = "with-i2c";
const char string43[] PROGMEM = "with-spi";
const char string44[] PROGMEM = "with-sd-card";
const char string45[] PROGMEM = "progn";
const char string46[] PROGMEM = "if";
const char string47[] PROGMEM = "cond";
const char string48[] PROGMEM = "when";
const char string49[] PROGMEM = "unless";
const char string50[] PROGMEM = "case";
const char string51[] PROGMEM = "and";
const char string52[] PROGMEM = "not";
const char string53[] PROGMEM = "null";
const char string54[] PROGMEM = "cons";
const char string55[] PROGMEM = "atom";
const char string56[] PROGMEM = "listp";
const char string57[] PROGMEM = "consp";
const char string58[] PROGMEM = "symbolp";
const char string59[] PROGMEM = "boundp";
const char string60[] PROGMEM = "keywordp";
const char string61[] PROGMEM = "streamp";
const char string62[] PROGMEM = "equal";
const char string63[] PROGMEM = "caar";
const char string64[] PROGMEM = "cadr";
const char string65[] PROGMEM = "second";
const char string66[] PROGMEM = "cdar";
const char string67[] PROGMEM = "cddr";
const char string68[] PROGMEM = "caaar";
const char string69[] PROGMEM = "caadr";
const char string70[] PROGMEM = "cadar";
const char string71[] PROGMEM = "caddr";
const char string72[] PROGMEM = "third";
const char string73[] PROGMEM = "cdaar";
const char string74[] PROGMEM = "cdadr";
const char string75[] PROGMEM = "cddar";
const char string76[] PROGMEM = "cdddr";
const char string77[] PROGMEM = "length";
const char string78[] PROGMEM = "list";
const char string79[] PROGMEM = "reverse";
const char string80[] PROGMEM = "assoc";
const char string81[] PROGMEM = "member";
const char string82[] PROGMEM = "apply";
const char string83[] PROGMEM = "funcall";
const char string84[] PROGMEM = "append";
const char string85[] PROGMEM = "mapc";
const char string86[] PROGMEM = "mapcar";
const char string87[] PROGMEM = "mapcan";
const char string88[] PROGMEM = "+";
const char string89[] PROGMEM = "-";
const char string90[] PROGMEM = "*";
const char string91[] PROGMEM = "/";
const char string92[] PROGMEM = "truncate";
const char string93[] PROGMEM = "mod";
const char string94[] PROGMEM = "1+";
const char string95[] PROGMEM = "1-";
const char string96[] PROGMEM = "abs";
const char string97[] PROGMEM = "random";
const char string98[] PROGMEM = "max";
const char string99[] PROGMEM = "min";
const char string100[] PROGMEM = "/=";
const char string101[] PROGMEM = "=";
const char string102[] PROGMEM = "<";
const char string103[] PROGMEM = "<=";
const char string104[] PROGMEM = ">";
const char string105[] PROGMEM = ">=";
const char string106[] PROGMEM = "plusp";
const char string107[] PROGMEM = "minusp";
const char string108[] PROGMEM = "zerop";
const char string109[] PROGMEM = "oddp";
const char string110[] PROGMEM = "evenp";
const char string111[] PROGMEM = "integerp";
const char string112[] PROGMEM = "numberp";
const char string113[] PROGMEM = "char-code";
const char string114[] PROGMEM = "code-char";
const char string115[] PROGMEM = "characterp";
const char string116[] PROGMEM = "stringp";
const char string117[] PROGMEM = "string=";
const char string118[] PROGMEM = "string<";
const char string119[] PROGMEM = "string>";
const char string120[] PROGMEM = "sort";
const char string121[] PROGMEM = "concatenate";
const char string122[] PROGMEM = "subseq";
const char string123[] PROGMEM = "read-from-string";
const char string124[] PROGMEM = "princ-to-string";
const char string125[] PROGMEM = "prin1-to-string";
const char string126[] PROGMEM = "logand";
const char string127[] PROGMEM = "logior";
const char string128[] PROGMEM = "logxor";
const char string129[] PROGMEM = "lognot";
const char string130[] PROGMEM = "ash";
const char string131[] PROGMEM = "logbitp";
const char string132[] PROGMEM = "eval";
const char string133[] PROGMEM = "return";
const char string134[] PROGMEM = "globals";
const char string135[] PROGMEM = "locals";
const char string136[] PROGMEM = "makunbound";
const char string137[] PROGMEM = "break";
const char string138[] PROGMEM = "read";
const char string139[] PROGMEM = "prin1";
const char string140[] PROGMEM = "print";
const char string141[] PROGMEM = "princ";
const char string142[] PROGMEM = "terpri";
const char string143[] PROGMEM = "read-byte";
const char string144[] PROGMEM = "read-line";
const char string145[] PROGMEM = "write-byte";
const char string146[] PROGMEM = "write-string";
const char string147[] PROGMEM = "write-line";
const char string148[] PROGMEM = "restart-i2c";
const char string149[] PROGMEM = "gc";
const char string150[] PROGMEM = "room";
const char string151[] PROGMEM = "save-image";
const char string152[] PROGMEM = "load-image";
const char string153[] PROGMEM = "cls";
const char string154[] PROGMEM = "digitalread";
const char string155[] PROGMEM = "analogreadresolution";
const char string156[] PROGMEM = "analogwrite";
const char string157[] PROGMEM = "dacreference";
const char string158[] PROGMEM = "delay";
const char string159[] PROGMEM = "millis";
const char string160[] PROGMEM = "sleep";
const char string161[] PROGMEM = "note";
const char string162[] PROGMEM = "edit";
const char string163[] PROGMEM = "pprint";
const char string164[] PROGMEM = "pprintall";
const char string165[] PROGMEM = "require";
const char string166[] PROGMEM = "list-library";
const char string167[] PROGMEM = ":led-builtin";
const char string168[] PROGMEM = ":high";
const char string169[] PROGMEM = ":low";
const char string170[] PROGMEM = ":input";
const char string171[] PROGMEM = ":input-pullup";
const char string172[] PROGMEM = ":output";
#if defined(CPU_ATmega328P)
const char string173[] PROGMEM = ":default";
const char string174[] PROGMEM = ":internal";
const char string175[] PROGMEM = ":external";
const char string176[] PROGMEM = ":portb";
const char string177[] PROGMEM = ":ddrb";
const char string178[] PROGMEM = ":pinb";
const char string179[] PROGMEM = ":portc";
const char string180[] PROGMEM = ":ddrc";
const char string181[] PROGMEM = ":pinc";
const char string182[] PROGMEM = ":portd";
const char string183[] PROGMEM = ":ddrd";
const char string184[] PROGMEM = ":pind";
#elif defined(CPU_ATmega1284P)
const char string173[] PROGMEM = ":default";
const char string174[] PROGMEM = ":internal1v1";
const char string175[] PROGMEM = ":internal2v56";
const char string176[] PROGMEM = ":external";
const char string177[] PROGMEM = ":porta";
const char string178[] PROGMEM = ":ddra";
const char string179[] PROGMEM = ":pina";
const char string180[] PROGMEM = ":portb";
const char string181[] PROGMEM = ":ddrb";
const char string182[] PROGMEM = ":pinb";
const char string183[] PROGMEM = ":portc";
const char string184[] PROGMEM = ":ddrc";
const char string185[] PROGMEM = ":pinc";
const char string186[] PROGMEM = ":portd";
const char string187[] PROGMEM = ":ddrd";
const char string188[] PROGMEM = ":pind";
#elif defined(CPU_ATmega2560)
const char string173[] PROGMEM = ":default";
const char string174[] PROGMEM = ":internal1v1";
const char string175[] PROGMEM = ":internal2v56";
const char string176[] PROGMEM = ":external";
const char string177[] PROGMEM = ":porta";
const char string178[] PROGMEM = ":ddra";
const char string179[] PROGMEM = ":pina";
const char string180[] PROGMEM = ":portb";
const char string181[] PROGMEM = ":ddrb";
const char string182[] PROGMEM = ":pinb";
const char string183[] PROGMEM = ":portc";
const char string184[] PROGMEM = ":ddrc";
const char string185[] PROGMEM = ":pinc";
const char string186[] PROGMEM = ":portd";
const char string187[] PROGMEM = ":ddrd";
const char string188[] PROGMEM = ":pind";
const char string189[] PROGMEM = ":porte";
const char string190[] PROGMEM = ":ddre";
const char string191[] PROGMEM = ":pine";
const char string192[] PROGMEM = ":portf";
const char string193[] PROGMEM = ":ddrf";
const char string194[] PROGMEM = ":pinf";
const char string195[] PROGMEM = ":portg";
const char string196[] PROGMEM = ":ddrg";
const char string197[] PROGMEM = ":ping";
const char string198[] PROGMEM = ":portj";
const char string199[] PROGMEM = ":ddrj";
const char string200[] PROGMEM = ":pinj";
#elif defined(CPU_ATmega4809)
const char string173[] PROGMEM = ":default";
const char string174[] PROGMEM = ":internal";
const char string175[] PROGMEM = ":vdd";
const char string176[] PROGMEM = ":internal0v55";
const char string177[] PROGMEM = ":internal1v1";
const char string178[] PROGMEM = ":internal1v5";
const char string179[] PROGMEM = ":internal2v5";
const char string180[] PROGMEM = ":internal4v3";
const char string181[] PROGMEM = ":external";
const char string182[] PROGMEM = ":porta-dir";
const char string183[] PROGMEM = ":porta-out";
const char string184[] PROGMEM = ":porta-in";
const char string185[] PROGMEM = ":portb-dir";
const char string186[] PROGMEM = ":portb-out";
const char string187[] PROGMEM = ":portb-in";
const char string188[] PROGMEM = ":portc-dir";
const char string189[] PROGMEM = ":portc-out";
const char string190[] PROGMEM = ":portc-in";
const char string191[] PROGMEM = ":portd-dir";
const char string192[] PROGMEM = ":portd-out";
const char string193[] PROGMEM = ":portd-in";
const char string194[] PROGMEM = ":porte-dir";
const char string195[] PROGMEM = ":porte-out";
const char string196[] PROGMEM = ":porte-in";
const char string197[] PROGMEM = ":portf-dir";
const char string198[] PROGMEM = ":portf-out";
const char string199[] PROGMEM = ":portf-in";
#elif defined(CPU_AVR128DX48)
const char string173[] PROGMEM = ":default";
const char string174[] PROGMEM = ":vdd";
const char string175[] PROGMEM = ":internal1v024";
const char string176[] PROGMEM = ":internal2v048";
const char string177[] PROGMEM = ":internal4v096";
const char string178[] PROGMEM = ":internal2v5";
const char string179[] PROGMEM = ":external";
const char string180[] PROGMEM = ":adc-dac0";
const char string181[] PROGMEM = ":adc-temperature";
const char string182[] PROGMEM = ":porta-dir";
const char string183[] PROGMEM = ":porta-out";
const char string184[] PROGMEM = ":porta-in";
const char string185[] PROGMEM = ":portb-dir";
const char string186[] PROGMEM = ":portb-out";
const char string187[] PROGMEM = ":portb-in";
const char string188[] PROGMEM = ":portc-dir";
const char string189[] PROGMEM = ":portc-out";
const char string190[] PROGMEM = ":portc-in";
const char string191[] PROGMEM = ":portd-dir";
const char string192[] PROGMEM = ":portd-out";
const char string193[] PROGMEM = ":portd-in";
const char string194[] PROGMEM = ":porte-dir";
const char string195[] PROGMEM = ":porte-out";
const char string196[] PROGMEM = ":porte-in";
const char string197[] PROGMEM = ":portf-dir";
const char string198[] PROGMEM = ":portf-out";
const char string199[] PROGMEM = ":portf-in";
#elif defined(CPU_ATtiny3227)
const char string173[] PROGMEM = ":flag";
#endif

// Built-in symbol lookup table
const tbl_entry_t lookup_table[] PROGMEM = {
  { string0, NULL, 0000 },
  { string1, NULL, 0000 },
  { string2, NULL, 0000 },
  { string3, NULL, 0000 },
  { string4, NULL, 0000 },
  { string5, NULL, 0017 },
  { string6, NULL, 0017 },
  { string7, NULL, 0017 },
  { string8, NULL, 0017 },
  { string9, sp_quote, 0311 },
  { string10, sp_defun, 0327 },
  { string11, sp_defvar, 0313 },
  { string12, fn_eq, 0222 },
  { string13, fn_car, 0211 },
  { string14, fn_car, 0211 },
  { string15, fn_cdr, 0211 },
  { string16, fn_cdr, 0211 },
  { string17, fn_nth, 0222 },
  { string18, fn_char, 0222 },
  { string19, fn_stringfn, 0211 },
  { string20, fn_pinmode, 0222 },
  { string21, fn_digitalwrite, 0222 },
  { string22, fn_analogread, 0211 },
  { string23, fn_analogreference, 0211 },
  { string24, fn_register, 0212 },
  { string25, fn_format, 0227 },
  { string26, sp_or, 0307 },
  { string27, sp_setq, 0327 },
  { string28, sp_loop, 0307 },
  { string29, sp_push, 0322 },
  { string30, sp_pop, 0311 },
  { string31, sp_incf, 0312 },
  { string32, sp_decf, 0312 },
  { string33, sp_setf, 0327 },
  { string34, sp_dolist, 0317 },
  { string35, sp_dotimes, 0317 },
  { string36, sp_trace, 0301 },
  { string37, sp_untrace, 0301 },
  { string38, sp_formillis, 0317 },
  { string39, sp_time, 0311 },
  { string40, sp_withoutputtostring, 0317 },
  { string41, sp_withserial, 0317 },
  { string42, sp_withi2c, 0317 },
  { string43, sp_withspi, 0317 },
  { string44, sp_withsdcard, 0327 },
  { string45, tf_progn, 0107 },
  { string46, tf_if, 0123 },
  { string47, tf_cond, 0107 },
  { string48, tf_when, 0117 },
  { string49, tf_unless, 0117 },
  { string50, tf_case, 0117 },
  { string51, tf_and, 0107 },
  { string52, fn_not, 0211 },
  { string53, fn_not, 0211 },
  { string54, fn_cons, 0222 },
  { string55, fn_atom, 0211 },
  { string56, fn_listp, 0211 },
  { string57, fn_consp, 0211 },
  { string58, fn_symbolp, 0211 },
  { string59, fn_boundp, 0211 },
  { string60, fn_keywordp, 0211 },
  { string61, fn_streamp, 0211 },
  { string62, fn_equal, 0222 },
  { string63, fn_caar, 0211 },
  { string64, fn_cadr, 0211 },
  { string65, fn_cadr, 0211 },
  { string66, fn_cdar, 0211 },
  { string67, fn_cddr, 0211 },
  { string68, fn_caaar, 0211 },
  { string69, fn_caadr, 0211 },
  { string70, fn_cadar, 0211 },
  { string71, fn_caddr, 0211 },
  { string72, fn_caddr, 0211 },
  { string73, fn_cdaar, 0211 },
  { string74, fn_cdadr, 0211 },
  { string75, fn_cddar, 0211 },
  { string76, fn_cdddr, 0211 },
  { string77, fn_length, 0211 },
  { string78, fn_list, 0207 },
  { string79, fn_reverse, 0211 },
  { string80, fn_assoc, 0224 },
  { string81, fn_member, 0224 },
  { string82, fn_apply, 0227 },
  { string83, fn_funcall, 0217 },
  { string84, fn_append, 0207 },
  { string85, fn_mapc, 0227 },
  { string86, fn_mapcar, 0227 },
  { string87, fn_mapcan, 0227 },
  { string88, fn_add, 0207 },
  { string89, fn_subtract, 0217 },
  { string90, fn_multiply, 0207 },
  { string91, fn_divide, 0227 },
  { string92, fn_divide, 0212 },
  { string93, fn_mod, 0222 },
  { string94, fn_oneplus, 0211 },
  { string95, fn_oneminus, 0211 },
  { string96, fn_abs, 0211 },
  { string97, fn_random, 0211 },
  { string98, fn_maxfn, 0217 },
  { string99, fn_minfn, 0217 },
  { string100, fn_noteq, 0217 },
  { string101, fn_numeq, 0217 },
  { string102, fn_less, 0217 },
  { string103, fn_lesseq, 0217 },
  { string104, fn_greater, 0217 },
  { string105, fn_greatereq, 0217 },
  { string106, fn_plusp, 0211 },
  { string107, fn_minusp, 0211 },
  { string108, fn_zerop, 0211 },
  { string109, fn_oddp, 0211 },
  { string110, fn_evenp, 0211 },
  { string111, fn_integerp, 0211 },
  { string112, fn_integerp, 0211 },
  { string113, fn_charcode, 0211 },
  { string114, fn_codechar, 0211 },
  { string115, fn_characterp, 0211 },
  { string116, fn_stringp, 0211 },
  { string117, fn_stringeq, 0222 },
  { string118, fn_stringless, 0222 },
  { string119, fn_stringgreater, 0222 },
  { string120, fn_sort, 0222 },
  { string121, fn_concatenate, 0217 },
  { string122, fn_subseq, 0223 },
  { string123, fn_readfromstring, 0211 },
  { string124, fn_princtostring, 0211 },
  { string125, fn_prin1tostring, 0211 },
  { string126, fn_logand, 0207 },
  { string127, fn_logior, 0207 },
  { string128, fn_logxor, 0207 },
  { string129, fn_lognot, 0211 },
  { string130, fn_ash, 0222 },
  { string131, fn_logbitp, 0222 },
  { string132, fn_eval, 0211 },
  { string133, fn_return, 0201 },
  { string134, fn_globals, 0200 },
  { string135, fn_locals, 0200 },
  { string136, fn_makunbound, 0211 },
  { string137, fn_break, 0200 },
  { string138, fn_read, 0201 },
  { string139, fn_prin1, 0212 },
  { string140, fn_print, 0212 },
  { string141, fn_princ, 0212 },
  { string142, fn_terpri, 0201 },
  { string143, fn_readbyte, 0202 },
  { string144, fn_readline, 0201 },
  { string145, fn_writebyte, 0212 },
  { string146, fn_writestring, 0212 },
  { string147, fn_writeline, 0212 },
  { string148, fn_restarti2c, 0212 },
  { string149, fn_gc, 0200 },
  { string150, fn_room, 0200 },
  { string151, fn_saveimage, 0201 },
  { string152, fn_loadimage, 0201 },
  { string153, fn_cls, 0200 },
  { string154, fn_digitalread, 0211 },
  { string155, fn_analogreadresolution, 0211 },
  { string156, fn_analogwrite, 0222 },
  { string157, fn_dacreference, 0211 },
  { string158, fn_delay, 0211 },
  { string159, fn_millis, 0200 },
  { string160, fn_sleep, 0201 },
  { string161, fn_note, 0203 },
  { string162, fn_edit, 0211 },
  { string163, fn_pprint, 0212 },
  { string164, fn_pprintall, 0201 },
  { string165, fn_require, 0211 },
  { string166, fn_listlibrary, 0200 },
  { string167, (fn_ptr_type)LED_BUILTIN, 0 },
  { string168, (fn_ptr_type)HIGH, DIGITALWRITE },
  { string169, (fn_ptr_type)LOW, DIGITALWRITE },
  { string170, (fn_ptr_type)INPUT, PINMODE },
  { string171, (fn_ptr_type)INPUT_PULLUP, PINMODE },
  { string172, (fn_ptr_type)OUTPUT, PINMODE },
#if defined(CPU_ATmega328P)
  { string173, (fn_ptr_type)DEFAULT, ANALOGREFERENCE },
  { string174, (fn_ptr_type)INTERNAL, ANALOGREFERENCE },
  { string175, (fn_ptr_type)EXTERNAL, ANALOGREFERENCE },
  { string176, (fn_ptr_type)&PORTB, REGISTER },
  { string177, (fn_ptr_type)&DDRB, REGISTER },
  { string178, (fn_ptr_type)&PINB, REGISTER },
  { string179, (fn_ptr_type)&PORTC, REGISTER },
  { string180, (fn_ptr_type)&DDRC, REGISTER },
  { string181, (fn_ptr_type)&PINC, REGISTER },
  { string182, (fn_ptr_type)&PORTD, REGISTER },
  { string183, (fn_ptr_type)&DDRD, REGISTER },
  { string184, (fn_ptr_type)&PIND, REGISTER },
#elif defined(CPU_ATmega1284P)
  { string173, (fn_ptr_type)DEFAULT, ANALOGREFERENCE },
  { string174, (fn_ptr_type)INTERNAL1V1, ANALOGREFERENCE },
  { string175, (fn_ptr_type)INTERNAL2V56, ANALOGREFERENCE },
  { string176, (fn_ptr_type)EXTERNAL, ANALOGREFERENCE },
  { string177, (fn_ptr_type)&PORTA, REGISTER },
  { string178, (fn_ptr_type)&DDRA, REGISTER },
  { string179, (fn_ptr_type)&PINA, REGISTER },
  { string180, (fn_ptr_type)&PORTB, REGISTER },
  { string181, (fn_ptr_type)&DDRB, REGISTER },
  { string182, (fn_ptr_type)&PINB, REGISTER },
  { string183, (fn_ptr_type)&PORTC, REGISTER },
  { string184, (fn_ptr_type)&DDRC, REGISTER },
  { string185, (fn_ptr_type)&PINC, REGISTER },
  { string186, (fn_ptr_type)&PORTD, REGISTER },
  { string187, (fn_ptr_type)&DDRD, REGISTER },
  { string188, (fn_ptr_type)&PIND, REGISTER },
#elif defined(CPU_ATmega2560)
  { string173, (fn_ptr_type)DEFAULT, ANALOGREFERENCE },
  { string174, (fn_ptr_type)INTERNAL1V1, ANALOGREFERENCE },
  { string175, (fn_ptr_type)INTERNAL2V56, ANALOGREFERENCE },
  { string176, (fn_ptr_type)EXTERNAL, ANALOGREFERENCE },
  { string177, (fn_ptr_type)&PORTA, REGISTER },
  { string178, (fn_ptr_type)&DDRA, REGISTER },
  { string179, (fn_ptr_type)&PINA, REGISTER },
  { string180, (fn_ptr_type)&PORTB, REGISTER },
  { string181, (fn_ptr_type)&DDRB, REGISTER },
  { string182, (fn_ptr_type)&PINB, REGISTER },
  { string183, (fn_ptr_type)&PORTC, REGISTER },
  { string184, (fn_ptr_type)&DDRC, REGISTER },
  { string185, (fn_ptr_type)&PINC, REGISTER },
  { string186, (fn_ptr_type)&PORTD, REGISTER },
  { string187, (fn_ptr_type)&DDRD, REGISTER },
  { string188, (fn_ptr_type)&PIND, REGISTER },
  { string189, (fn_ptr_type)&PORTE, REGISTER },
  { string190, (fn_ptr_type)&DDRE, REGISTER },
  { string191, (fn_ptr_type)&PINE, REGISTER },
  { string192, (fn_ptr_type)&PORTF, REGISTER },
  { string193, (fn_ptr_type)&DDRF, REGISTER },
  { string194, (fn_ptr_type)&PINF, REGISTER },
  { string195, (fn_ptr_type)&PORTG, REGISTER },
  { string196, (fn_ptr_type)&DDRG, REGISTER },
  { string197, (fn_ptr_type)&PING, REGISTER },
  { string198, (fn_ptr_type)&PORTJ, REGISTER },
  { string199, (fn_ptr_type)&DDRJ, REGISTER },
  { string200, (fn_ptr_type)&PINJ, REGISTER },
#elif defined(CPU_ATmega4809)
  { string173, (fn_ptr_type)DEFAULT, ANALOGREFERENCE },
  { string174, (fn_ptr_type)INTERNAL, ANALOGREFERENCE },
  { string175, (fn_ptr_type)VDD, ANALOGREFERENCE },
  { string176, (fn_ptr_type)INTERNAL0V55, ANALOGREFERENCE },
  { string177, (fn_ptr_type)INTERNAL1V1, ANALOGREFERENCE },
  { string178, (fn_ptr_type)INTERNAL1V5, ANALOGREFERENCE },
  { string179, (fn_ptr_type)INTERNAL2V5, ANALOGREFERENCE },
  { string180, (fn_ptr_type)INTERNAL4V3, ANALOGREFERENCE },
  { string181, (fn_ptr_type)EXTERNAL, ANALOGREFERENCE },
  { string182, (fn_ptr_type)&PORTA_DIR, REGISTER },
  { string183, (fn_ptr_type)&PORTA_OUT, REGISTER },
  { string184, (fn_ptr_type)&PORTA_IN, REGISTER },
  { string185, (fn_ptr_type)&PORTB_DIR, REGISTER },
  { string186, (fn_ptr_type)&PORTB_OUT, REGISTER },
  { string187, (fn_ptr_type)&PORTB_IN, REGISTER },
  { string188, (fn_ptr_type)&PORTC_DIR, REGISTER },
  { string189, (fn_ptr_type)&PORTC_OUT, REGISTER },
  { string190, (fn_ptr_type)&PORTC_IN, REGISTER },
  { string191, (fn_ptr_type)&PORTD_DIR, REGISTER },
  { string192, (fn_ptr_type)&PORTD_OUT, REGISTER },
  { string193, (fn_ptr_type)&PORTD_IN, REGISTER },
  { string194, (fn_ptr_type)&PORTE_DIR, REGISTER },
  { string195, (fn_ptr_type)&PORTE_OUT, REGISTER },
  { string196, (fn_ptr_type)&PORTE_IN, REGISTER },
  { string197, (fn_ptr_type)&PORTF_DIR, REGISTER },
  { string198, (fn_ptr_type)&PORTF_OUT, REGISTER },
  { string199, (fn_ptr_type)&PORTF_IN, REGISTER },
#elif defined(CPU_AVR128DX48)
  { string173, (fn_ptr_type)DEFAULT, ANALOGREFERENCE },
  { string174, (fn_ptr_type)VDD, ANALOGREFERENCE },
  { string175, (fn_ptr_type)INTERNAL1V024, ANALOGREFERENCE },
  { string176, (fn_ptr_type)INTERNAL2V048, ANALOGREFERENCE },
  { string177, (fn_ptr_type)INTERNAL4V096, ANALOGREFERENCE },
  { string178, (fn_ptr_type)INTERNAL2V5, ANALOGREFERENCE },
  { string179, (fn_ptr_type)EXTERNAL, ANALOGREFERENCE },
  { string180, (fn_ptr_type)ADC_DAC0, ANALOGREAD },
  { string181, (fn_ptr_type)ADC_TEMPERATURE, ANALOGREAD },
  { string182, (fn_ptr_type)&PORTA_DIR, REGISTER },
  { string183, (fn_ptr_type)&PORTA_OUT, REGISTER },
  { string184, (fn_ptr_type)&PORTA_IN, REGISTER },
  { string185, (fn_ptr_type)&PORTB_DIR, REGISTER },
  { string186, (fn_ptr_type)&PORTB_OUT, REGISTER },
  { string187, (fn_ptr_type)&PORTB_IN, REGISTER },
  { string188, (fn_ptr_type)&PORTC_DIR, REGISTER },
  { string189, (fn_ptr_type)&PORTC_OUT, REGISTER },
  { string190, (fn_ptr_type)&PORTC_IN, REGISTER },
  { string191, (fn_ptr_type)&PORTD_DIR, REGISTER },
  { string192, (fn_ptr_type)&PORTD_OUT, REGISTER },
  { string193, (fn_ptr_type)&PORTD_IN, REGISTER },
  { string194, (fn_ptr_type)&PORTE_DIR, REGISTER },
  { string195, (fn_ptr_type)&PORTE_OUT, REGISTER },
  { string196, (fn_ptr_type)&PORTE_IN, REGISTER },
  { string197, (fn_ptr_type)&PORTF_DIR, REGISTER },
  { string198, (fn_ptr_type)&PORTF_OUT, REGISTER },
  { string199, (fn_ptr_type)&PORTF_IN, REGISTER },
#elif defined(CPU_ATtiny3227)
  { string173, (fn_ptr_type)&FLAG, REGISTER },
#endif
};

// Table lookup functions

builtin_t lookupbuiltin (char* n) {
  int entries = arraysize(lookup_table);
  for (int entry = 0; entry < entries; entry++) {
    #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
    if (strcasecmp(n, (char*)lookup_table[entry].string) == 0)
    #else
    if (strcasecmp_P(n, (char*)pgm_read_ptr(&lookup_table[entry].string)) == 0)
    #endif
    return (builtin_t)entry;
  }
  return ENDFUNCTIONS;
}

intptr_t lookupfn (builtin_t name) {
  #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
  return (intptr_t)lookup_table[name].fptr;
  #else
  return (intptr_t)pgm_read_ptr(&lookup_table[name].fptr);
  #endif
}

uint8_t getminmax (builtin_t name) {
  #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
  return lookup_table[name].minmax;
  #else
  return pgm_read_byte(&lookup_table[name].minmax);
  #endif
}

void checkminmax (builtin_t name, int nargs) {
  if (!(name < ENDFUNCTIONS)) error2(PSTR("not a builtin"));
  uint8_t minmax = getminmax(name);
  if (nargs<((minmax >> 3) & 0x07)) error2(toofewargs);
  if ((minmax & 0x07) != 0x07 && nargs>(minmax & 0x07)) error2(toomanyargs);
}

void testescape () {
  if (Serial.available() && Serial.read() == '~') error2(PSTR("escape!"));
}

bool keywordp (object *obj) {
  if (!(symbolp(obj) && builtinp(obj->name))) return false;
  builtin_t name = builtin(obj->name);
  #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
  PGM_P s = lookup_table[name].string;
  char c = s[0];
  #else
  PGM_P s = (char*)pgm_read_ptr(&lookup_table[name].string);
  char c = pgm_read_byte(s);
  #endif
  return (c == ':');
}

// Main evaluator

extern char __bss_end[];

object *eval (object *form, object *env) {
  uint8_t sp[0];
  int TC=0;
  EVAL:
  // Enough space?
  //Serial.println((uint16_t)sp - (uint16_t)__bss_end); // Find best STACKDIFF value
  if ((uint16_t)sp - (uint16_t)__bss_end < STACKDIFF) { Context = NIL; error2(PSTR("stack overflow")); }
  if (Freespace <= WORKSPACESIZE>>4) gc(form, env);      // GC when 1/16 of workspace left
  // Escape
  if (tstflag(ESCAPE)) { clrflag(ESCAPE); error2(PSTR("escape!"));}
  if (!tstflag(NOESC)) testescape();

  if (form == NULL) return nil;

  if (form->type >= NUMBER && form->type <= STRING) return form;

  if (symbolp(form)) {
    symbol_t name = form->name;
    object *pair = value(name, env);
    if (pair != NULL) return cdr(pair);
    pair = value(name, GlobalEnv);
    if (pair != NULL) return cdr(pair);
    else if (builtinp(name)) return form;
    Context = NIL;
    error(PSTR("undefined"), form);
  }

  #if defined(CODESIZE)
  if (form->type == CODE) error2(PSTR("can't evaluate CODE header"));
  #endif

  // It's a list
  object *function = car(form);
  object *args = cdr(form);

  if (function == NULL) error(PSTR("illegal function"), nil);
  if (!listp(args)) error(PSTR("can't evaluate a dotted pair"), args);

  // List starts with a builtin symbol?
  if (symbolp(function) && builtinp(function->name)) {
    builtin_t name = builtin(function->name);

    if ((name == LET) || (name == LETSTAR)) {
      int TCstart = TC;
      if (args == NULL) error2(noargument);
      object *assigns = first(args);
      if (!listp(assigns)) error(notalist, assigns);
      object *forms = cdr(args);
      object *newenv = env;
      protect(newenv);
      while (assigns != NULL) {
        object *assign = car(assigns);
        if (!consp(assign)) push(cons(assign,nil), newenv);
        else if (cdr(assign) == NULL) push(cons(first(assign),nil), newenv);
        else push(cons(first(assign),eval(second(assign),env)), newenv);
        car(GCStack) = newenv;
        if (name == LETSTAR) env = newenv;
        assigns = cdr(assigns);
      }
      env = newenv;
      unprotect();
      form = tf_progn(forms,env);
      TC = TCstart;
      goto EVAL;
    }

    if (name == LAMBDA) {
      if (env == NULL) return form;
      object *envcopy = NULL;
      while (env != NULL) {
        object *pair = first(env);
        if (pair != NULL) push(pair, envcopy);
        env = cdr(env);
      }
      return cons(bsymbol(CLOSURE), cons(envcopy,args));
    }
    uint8_t fntype = getminmax(name)>>6;

    if (fntype == SPECIAL_FORMS) {
      Context = name;
      checkargs(args);
      return ((fn_ptr_type)lookupfn(name))(args, env);
    }

    if (fntype == TAIL_FORMS) {
      Context = name;
      checkargs(args);
      form = ((fn_ptr_type)lookupfn(name))(args, env);
      TC = 1;
      goto EVAL;
    }
    if (fntype == OTHER_FORMS) error(PSTR("can't be used as a function"), function);
  }

  // Evaluate the parameters - result in head
  object *fname = car(form);
  int TCstart = TC;
  object *head = cons(eval(fname, env), NULL);
  protect(head); // Don't GC the result list
  object *tail = head;
  form = cdr(form);
  int nargs = 0;

  while (form != NULL){
    object *obj = cons(eval(car(form),env),NULL);
    cdr(tail) = obj;
    tail = obj;
    form = cdr(form);
    nargs++;
  }

  function = car(head);
  args = cdr(head);

  if (symbolp(function)) {
    builtin_t bname = builtin(function->name);
    if (!builtinp(function->name)) error(PSTR("not valid here"), fname);
    Context = bname;
    checkminmax(bname, nargs);
    object *result = ((fn_ptr_type)lookupfn(bname))(args, env);
    unprotect();
    return result;
  }

  if (consp(function)) {
    symbol_t name = sym(NIL);
    if (!listp(fname)) name = fname->name;

    if (isbuiltin(car(function), LAMBDA)) {
      form = closure(TCstart, name, function, args, &env);
      unprotect();
      int trace = tracing(fname->name);
      if (trace) {
        object *result = eval(form, env);
        indent((--(TraceDepth[trace-1]))<<1, ' ', pserial);
        pint(TraceDepth[trace-1], pserial);
        pserial(':'); pserial(' ');
        printobject(fname, pserial); pfstring(PSTR(" returned "), pserial);
        printobject(result, pserial); pln(pserial);
        return result;
      } else {
        TC = 1;
        goto EVAL;
      }
    }

    if (isbuiltin(car(function), CLOSURE)) {
      function = cdr(function);
      form = closure(TCstart, name, function, args, &env);
      unprotect();
      TC = 1;
      goto EVAL;
    }

  }
  error(PSTR("illegal function"), fname); return nil;
}

// Print functions

void pserial (char c) {
  LastPrint = c;
  if (c == '\n') Serial.write('\r');
  Serial.write(c);
}

const char ControlCodes[] PROGMEM = "Null\0SOH\0STX\0ETX\0EOT\0ENQ\0ACK\0Bell\0Backspace\0Tab\0Newline\0VT\0"
"Page\0Return\0SO\0SI\0DLE\0DC1\0DC2\0DC3\0DC4\0NAK\0SYN\0ETB\0CAN\0EM\0SUB\0Escape\0FS\0GS\0RS\0US\0Space\0";

void pcharacter (uint8_t c, pfun_t pfun) {
  if (!tstflag(PRINTREADABLY)) pfun(c);
  else {
    pfun('#'); pfun('\\');
    if (c <= 32) {
      PGM_P p = ControlCodes;
      #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
      while (c > 0) {p = p + strlen(p) + 1; c--; }
      #else
      while (c > 0) {p = p + strlen_P(p) + 1; c--; }
      #endif
      pfstring(p, pfun);
    } else if (c < 127) pfun(c);
    else pint(c, pfun);
  }
}

void pstring (char *s, pfun_t pfun) {
  while (*s) pfun(*s++);
}

void plispstring (object *form, pfun_t pfun) {
  plispstr(form->name, pfun);
}

void plispstr (symbol_t name, pfun_t pfun) {
  object *form = (object *)name;
  while (form != NULL) {
    int chars = form->chars;
    for (int i=(sizeof(int)-1)*8; i>=0; i=i-8) {
      char ch = chars>>i & 0xFF;
      if (tstflag(PRINTREADABLY) && (ch == '"' || ch == '\\')) pfun('\\');
      if (ch) pfun(ch);
    }
    form = car(form);
  }
}

void printstring (object *form, pfun_t pfun) {
  if (tstflag(PRINTREADABLY)) pfun('"');
  plispstr(form->name, pfun);
  if (tstflag(PRINTREADABLY)) pfun('"');
}

void pbuiltin (builtin_t name, pfun_t pfun) {
  #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
  PGM_P s = lookup_table[name].string;
  #else
  PGM_P s = (char*)pgm_read_ptr(&lookup_table[name].string);
  #endif
  while (1) {
    #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
    char c = *s++;
    #else
    char c = pgm_read_byte(s++);
    #endif
    if (c == 0) return;
    pfun(c);
  }
}

void pradix40 (symbol_t name, pfun_t pfun) {
  uint16_t x = untwist(name);
  for (int d=1600; d>0; d = d/40) {
    uint16_t j = x/d;
    char c = fromradix40(j);
    if (c == 0) return;
    pfun(c); x = x - j*d;
  }
}

void printsymbol (object *form, pfun_t pfun) {
  psymbol(form->name, pfun);
}

void psymbol (symbol_t name, pfun_t pfun) {
  if (longnamep(name)) plispstr(name, pfun);
  else {
    uint16_t value = untwist(name);
    if (value < PACKEDS) error2(PSTR("invalid symbol"));
    else if (value >= BUILTINS) pbuiltin((builtin_t)(value-BUILTINS), pfun);
    else pradix40(name, pfun);
  }
}

void pfstring (PGM_P s, pfun_t pfun) {
  while (1) {
    #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
    char c = *s++;
    #else
    char c = pgm_read_byte(s++);
    #endif
    if (c == 0) return;
    pfun(c);
  }
}

void pint (int i, pfun_t pfun) {
  uint16_t j = i;
  if (i<0) { pfun('-'); j=-i; }
  pintbase(j, 10, pfun);
}

void pintbase (uint16_t i, uint8_t base, pfun_t pfun) {
  uint8_t lead = 0; uint16_t p = 10000;
  if (base == 2) p = 0x8000; else if (base == 16) p = 0x1000;
  for (uint16_t d=p; d>0; d=d/base) {
    uint16_t j = i/d;
    if (j!=0 || lead || d==1) { pfun((j<10) ? j+'0' : j+'W'); lead=1;}
    i = i - j*d;
  }
}

void printhex2 (int i, pfun_t pfun) {
  for (unsigned int d=0x10; d>0; d=d>>4) {
    unsigned int j = i/d;
    pfun((j<10) ? j+'0' : j+'W'); 
    i = i - j*d;
  }
}

inline void pln (pfun_t pfun) {
  pfun('\n');
}

void pfl (pfun_t pfun) {
  if (LastPrint != '\n') pfun('\n');
}

void plist (object *form, pfun_t pfun) {
  pfun('(');
  printobject(car(form), pfun);
  form = cdr(form);
  while (form != NULL && listp(form)) {
    pfun(' ');
    printobject(car(form), pfun);
    form = cdr(form);
  }
  if (form != NULL) {
    pfstring(PSTR(" . "), pfun);
    printobject(form, pfun);
  }
  pfun(')');
}

void pstream (object *form, pfun_t pfun) {
  pfun('<');
  #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
  PGM_P s = streamname[(form->integer)>>8];
  #else
  PGM_P s = (char*)pgm_read_ptr(&streamname[(form->integer)>>8]);
  #endif
  pfstring(s, pfun);
  pfstring(PSTR("-stream "), pfun);
  pint(form->integer & 0xFF, pfun);
  pfun('>');
}

void printobject (object *form, pfun_t pfun) {
  if (form == NULL) pfstring(PSTR("nil"), pfun);
  else if (listp(form) && isbuiltin(car(form), CLOSURE)) pfstring(PSTR("<closure>"), pfun);
  else if (listp(form)) plist(form, pfun);
  else if (integerp(form)) pint(form->integer, pfun);
  else if (symbolp(form)) { if (form->name != sym(NOTHING)) printsymbol(form, pfun); }
  else if (characterp(form)) pcharacter(form->chars, pfun);
  else if (stringp(form)) printstring(form, pfun);
  #if defined(CODESIZE)
  else if (form->type == CODE) pfstring(PSTR("code"), pfun);
  #endif
  else if (streamp(form)) pstream(form, pfun);
  else error2(PSTR("error in print"));
}

void prin1object (object *form, pfun_t pfun) {
  char temp = Flags;
  clrflag(PRINTREADABLY);
  printobject(form, pfun);
  Flags = temp;
}

// Read functions

int glibrary () {
  if (LastChar) {
    char temp = LastChar;
    LastChar = 0;
    return temp;
  }
  #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
  char c = LispLibrary[GlobalStringIndex++];
  #else
  char c = pgm_read_byte(&LispLibrary[GlobalStringIndex++]);
  #endif
  return (c != 0) ? c : -1; // -1?
}

void loadfromlibrary (object *env) {
  GlobalStringIndex = 0;
  object *line = read(glibrary);
  while (line != NULL) {
    protect(line);
    eval(line, env);
    unprotect();
    line = read(glibrary);
  }
}

// For line editor
const int TerminalWidth = 80;
volatile int WritePtr = 0, ReadPtr = 0, LastWritePtr = 0;
const int KybdBufSize = 333; // 42*8 - 3
char KybdBuf[KybdBufSize];
volatile uint8_t KybdAvailable = 0;

// Parenthesis highlighting
void esc (int p, char c) {
  Serial.write('\e'); Serial.write('[');
  Serial.write((char)('0'+ p/100));
  Serial.write((char)('0'+ (p/10) % 10));
  Serial.write((char)('0'+ p % 10));
  Serial.write(c);
}

void hilight (char c) {
  Serial.write('\e'); Serial.write('['); Serial.write(c); Serial.write('m');
}

void Highlight (int p, int wp, uint8_t invert) {
  wp = wp + 2; // Prompt
#if defined (printfreespace)
  int f = Freespace;
  while (f) { wp++; f=f/10; }
#endif
  int line = wp/TerminalWidth;
  int col = wp%TerminalWidth;
  int targetline = (wp - p)/TerminalWidth;
  int targetcol = (wp - p)%TerminalWidth;
  int up = line-targetline, left = col-targetcol;
  if (p) {
    if (up) esc(up, 'A');
    if (col > targetcol) esc(left, 'D'); else esc(-left, 'C');
    if (invert) hilight('7');
    Serial.write('('); Serial.write('\b');
    // Go back
    if (up) esc(up, 'B'); // Down
    if (col > targetcol) esc(left, 'C'); else esc(-left, 'D');
    Serial.write('\b'); Serial.write(')');
    if (invert) hilight('0');
  }
}

void processkey (char c) {
  if (c == 27) { setflag(ESCAPE); return; }    // Escape key
#if defined(vt100)
  static int parenthesis = 0, wp = 0;
  // Undo previous parenthesis highlight
  Highlight(parenthesis, wp, 0);
  parenthesis = 0;
#endif
  // Edit buffer
  if (c == '\n' || c == '\r') {
    pserial('\n');
    KybdAvailable = 1;
    ReadPtr = 0; LastWritePtr = WritePtr;
    return;
  }
  if (c == 8 || c == 0x7f) {     // Backspace key
    if (WritePtr > 0) {
      WritePtr--;
      Serial.write(8); Serial.write(' '); Serial.write(8);
      if (WritePtr) c = KybdBuf[WritePtr-1];
    }
  } else if (c == 9) { // tab or ctrl-I
    for (int i = 0; i < LastWritePtr; i++) Serial.write(KybdBuf[i]);
    WritePtr = LastWritePtr;
  } else if (WritePtr < KybdBufSize) {
    KybdBuf[WritePtr++] = c;
    Serial.write(c);
  }
#if defined(vt100)
  // Do new parenthesis highlight
  if (c == ')') {
    int search = WritePtr-1, level = 0;
    while (search >= 0 && parenthesis == 0) {
      c = KybdBuf[search--];
      if (c == ')') level++;
      if (c == '(') {
        level--;
        if (level == 0) {parenthesis = WritePtr-search-1; wp = WritePtr; }
      }
    }
    Highlight(parenthesis, wp, 1);
  }
#endif
  return;
}

int gserial () {
  if (LastChar) {
    char temp = LastChar;
    LastChar = 0;
    return temp;
  }
#if defined(lineeditor)
  while (!KybdAvailable) {
    while (!Serial.available());
    char temp = Serial.read();
    processkey(temp);
  }
  if (ReadPtr != WritePtr) return KybdBuf[ReadPtr++];
  KybdAvailable = 0;
  WritePtr = 0;
  return '\n';
#elif defined(CPU_ATmega328P) || defined(CPU_ATtiny3227)
  while (!Serial.available());
  char temp = Serial.read();
  if (temp != '\n') pserial(temp);
  return temp;
#else
  unsigned long start = millis();
  while (!Serial.available()) if (millis() - start > 1000) clrflag(NOECHO);
  char temp = Serial.read();
  if (temp != '\n' && !tstflag(NOECHO)) pserial(temp);
  return temp;
#endif
}

object *nextitem (gfun_t gfun) {
  int ch = gfun();
  while(issp(ch)) ch = gfun();

  #if defined(CPU_ATmega328P) || defined(CPU_ATtiny3227)
  if (ch == ';') {
    while(ch != '(') ch = gfun();
  }
  #else
  if (ch == ';') {
    do { ch = gfun(); if (ch == ';' || ch == '(') setflag(NOECHO); }
    while(ch != '(');
  }
  #endif
  if (ch == '\n') ch = gfun();
  if (ch == -1) return nil;
  if (ch == ')') return (object *)KET;
  if (ch == '(') return (object *)BRA;
  if (ch == '\'') return (object *)QUO;
  if (ch == '.') return (object *)DOT;

  // Parse string
  if (ch == '"') return readstring('"', true, gfun);

  // Parse symbol, character, or number
  int index = 0, base = 10, sign = 1;
  char buffer[BUFFERSIZE];
  int bufmax = BUFFERSIZE-1; // Max index
  unsigned int result = 0;
  if (ch == '+' || ch == '-') {
    buffer[index++] = ch;
    if (ch == '-') sign = -1;
    ch = gfun();
  }

  // Parse reader macros
  else if (ch == '#') {
    ch = gfun();
    char ch2 = ch & ~0x20; // force to upper case
    if (ch == '\\') { // Character
      base = 0; ch = gfun();
      if (issp(ch) || isbr(ch)) return character(ch);
      else LastChar = ch;
    } else if (ch == '|') {
      do { while (gfun() != '|'); }
      while (gfun() != '#');
      return nextitem(gfun);
    } else if (ch2 == 'B') base = 2;
    else if (ch2 == 'O') base = 8;
    else if (ch2 == 'X') base = 16;
    else if (ch == '\'') return nextitem(gfun);
    else if (ch == '.') {
      setflag(NOESC);
      object *result = eval(read(gfun), NULL);
      clrflag(NOESC);
      return result;
    } else error2(PSTR("illegal character after #"));
    ch = gfun();
  }

  int isnumber = (digitvalue(ch)<base);
  buffer[2] = '\0'; // In case symbol is one letter

  while(!issp(ch) && !isbr(ch) && index < bufmax) {
    buffer[index++] = ch;
    int temp = digitvalue(ch);
    result = result * base + temp;
    isnumber = isnumber && (digitvalue(ch)<base);
    ch = gfun();
  }

  buffer[index] = '\0';
  if (isbr(ch)) LastChar = ch;

  if (isnumber) {
    if (base == 10 && result > ((unsigned int)INT_MAX+(1-sign)/2)) 
      error2(PSTR("Number out of range"));
    return number(result*sign);
  } else if (base == 0) {
    if (index == 1) return character(buffer[0]);
    PGM_P p = ControlCodes; char c = 0;
    while (c < 33) {
      #if defined(CPU_ATmega4809) || defined(CPU_ATtiny3227)
      if (strcasecmp(buffer, p) == 0) return character(c);
      p = p + strlen(p) + 1; c++;
      #else
      if (strcasecmp_P(buffer, p) == 0) return character(c);
      p = p + strlen_P(p) + 1; c++;
      #endif
    }
    if (index == 3) return character((buffer[0]*10+buffer[1])*10+buffer[2]-5328);
    error2(PSTR("unknown character"));
  }

  builtin_t x = lookupbuiltin(buffer);
  if (x == NIL) return nil;
  if (x != ENDFUNCTIONS) return bsymbol(x);
  if (index <= 3 && valid40(buffer)) return intern(twist(pack40(buffer)));
  buffer[index+1] = '\0'; // For internlong
  return internlong(buffer);
}

object *readrest (gfun_t gfun) {
  object *item = nextitem(gfun);
  object *head = NULL;
  object *tail = NULL;

  while (item != (object *)KET) {
    if (item == (object *)BRA) {
      item = readrest(gfun);
    } else if (item == (object *)QUO) {
      item = cons(bsymbol(QUOTE), cons(read(gfun), NULL));
    } else if (item == (object *)DOT) {
      tail->cdr = read(gfun);
      if (readrest(gfun) != NULL) error2(PSTR("malformed list"));
      return head;
    } else {
      object *cell = cons(item, NULL);
      if (head == NULL) head = cell;
      else tail->cdr = cell;
      tail = cell;
      item = nextitem(gfun);
    }
  }
  return head;
}

object *read (gfun_t gfun) {
  object *item = nextitem(gfun);
  if (item == (object *)KET) error2(PSTR("incomplete list"));
  if (item == (object *)BRA) return readrest(gfun);
  if (item == (object *)DOT) return read(gfun);
  if (item == (object *)QUO) return cons(bsymbol(QUOTE), cons(read(gfun), NULL));
  return item;
}

// Setup

void initenv () {
  GlobalEnv = NULL;
  tee = bsymbol(TEE);
}

// Entry point from the Arduino IDE
void setup () {
  Serial.begin(9600);
  int start = millis();
  while ((millis() - start) < 5000) { if (Serial) break; }
  initworkspace();
  initenv();
  initsleep();
  pfstring(PSTR("uLisp 4.6 "), pserial); pln(pserial);
}

// Read/Evaluate/Print loop

void repl (object *env) {
  for (;;) {
    RandomSeed = micros();
    gc(NULL, env);
    #if defined(printfreespace)
    pint(Freespace, pserial);
    #endif
    if (BreakLevel) {
      pfstring(PSTR(" : "), pserial);
      pint(BreakLevel, pserial);
    }
    pserial('>'); pserial(' ');
    Context = NIL;
    object *line = read(gserial);
    if (BreakLevel && line == nil) { pln(pserial); return; }
    if (line == (object *)KET) error2(PSTR("unmatched right bracket"));
    protect(line);
    pfl(pserial);
    line = eval(line, env);
    pfl(pserial);
    printobject(line, pserial);
    unprotect();
    pfl(pserial);
    pln(pserial);
  }
}

void loop () {
  if (!setjmp(exception)) {
    #if defined(resetautorun)
    volatile int autorun = 12; // Fudge to keep code size the same
    #else
    volatile int autorun = 13;
    #endif
    if (autorun == 12) autorunimage();
  }
  ulisperror();
  repl(NULL);
}

void ulisperror () {
  // Come here after error
  #if defined (serialmonitor)
  delay(100); while (Serial.available()) Serial.read();
  #endif
  clrflag(NOESC); BreakLevel = 0;
  for (int i=0; i<TRACEMAX; i++) TraceDepth[i] = 0;
  #if defined(sdcardsupport)
  SDpfile.close(); SDgfile.close();
  #endif
  #if defined(lisplibrary)
  if (!tstflag(LIBRARYLOADED)) { setflag(LIBRARYLOADED); loadfromlibrary(NULL); clrflag(NOECHO); }
  #endif
}