Kuan

	Tiny dynamic s-expression programming language, with delusions of grandeur.

Inspirations: Chika, Ephem, Wren

Aspiration: Insitux

Goals & Features

(NYA) - Not Yet Achieved

• S-expressions
• Speed
• ARC memory management
• REPL
• Collections (NYA)
  • List
  • Map
  • Network stream
  • File stream
• Anonymous functions
  • Closures (NYA)
• Easy imports (NYA)
• Program errors (NYA)
• Type-checking (NYA)
  • Parsetime (NYA)
  • Parsetime-calculated runtime (NYA)

Approaches

• Bytecode
  • Different native operations for fixed-arg and varadic
• Computed GOTO's
• Double-only arithmetic
  • NaN tagging
• ARC mem management only where objs are args
  • ARC mem leak check upon termination
• Valgrind memleak checks

Usage

Ubuntu/Debian
git clone --depth=1 https://github.com/phunanon/Kuan
Ensure CMake in installed on your system.
Run ./init.sh. If needing to subsequently recompile use ./make.sh.
Execute ./build/kuan in the terminal for the REPL;
with a file path as the command-line argument to parse and execute,
optionally with -r as the second argument to return last value;
or with code as string e.g. ./build/kuan "(+ 1 1)".

Syntax and native operations

Literals and values

Representations	Data type
T F N	true, false, nil
\a	character
0x1 or 0x12	8 bit unsigned integer
3.14 or .14 or -3.14 or -.14	64 bit signed real
0x3.AB or -3.AB (hex)	64 bit signed real
[1 \a "hello"]	vector
%	first parameter
%N	Nth parameter
args	vector of arguments

• Note: referencing more parameters than arguments given is undefined behaviour

Functions and native operations

Glossary
[…] representation of a vector.
[0..] zero or more arguments.
[1..] one or more arguments.
[arg-name] optional argument.
"truthy" is a value that is not F or N.
"falsey" is a value that is F or N.

Expressions

An evaluated expression returns a value. An expression is formed as (operation [0..]) whereby the operation can be a native operation, program function, variable containing a function or lambda reference, or another expression evaluated as one of the aforementioned. Arguments can also be expressions.

Functions

Function declarations are only accepted at the top-level of a document or REPL interaction - they cannot be contained within expressions.
They are declared as
(fn function-name […] [1..]) or (fn function-name [1..])
where […] is a vector of parameters (e.g. [a b c]), and [1..] is one or more expressions.

Anonymous functions, or lambdas, are defined by the syntax #(operation [0..]) which constitutes one expression.

Short-circuited control structures

(if cond if-true [if-false])
Returns if-true if cond is truthy, or if-false or N if cond is falsey.
if-true and if-false are never mutually evaluated.

Benchmarks

As of 5th August 2020. Most using hyperfine with 3 warmups, 10 runs.
Janet added 6th Oct 2021.

What	C	Kuan	NodeJS	Wren	Janet	pypy3	Clojure	C#
fib 35	35ms	632ms	168ms	1327ms	1474ms	250ms	3s, 143ms warm	2.6s, 95ms warm

Kuan / Janet (almost) / Clojure (almost)

(fn fib [n]
  (if (< n 2) n
    (+ (fib (- n 1))
       (fib (- n 2)))))
(println (fib 35))

C

#include "stdio.h"
double fib (double n) {
  return n < 2 ? n : fib(n - 1) + fib(n - 2);
}
int main () {
  printf("%f\n", fib(35));
}

Wren

class Fib {
  static get(n) {
    if (n < 2) return n
    return get(n - 1) + get(n - 2)
  }
}
System.print(Fib.get(35))

Python3

def fib(n):
  return n if n < 2 else fib(n - 1) + fib(n - 2)
print(fib(35))

C#

static int fib (int n) => n < 2 ? n : fib(n - 1) + fib(n - 2);
static void Main () => Console.WriteLine(fib(35));