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Refactor Transform String Resugar Term Scott (#714)
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Co-authored-by: Nicolas Abril <y906846m@anonaddy.me>
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@Liberxue @developedby
Liberxue and developedby committed Sep 17, 2024
1 parent d91742e commit 2b401e7
Showing 1 changed file with 101 additions and 186 deletions.
287 changes: 101 additions & 186 deletions src/fun/transform/resugar_string.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,237 +4,152 @@ use crate::{
};

impl Term {
/// Converts lambda-encoded strings ending with String/nil to a string literals.
/// Converts lambda-encoded strings ending with String/nil to string literals.
pub fn resugar_strings(&mut self, adt_encoding: AdtEncoding) {
match adt_encoding {
AdtEncoding::Scott => self.resugar_strings_scott(),
AdtEncoding::NumScott => self.resugar_strings_num_scott(),
AdtEncoding::Scott => self.try_resugar_strings_with(Self::resugar_strings_scott),
AdtEncoding::NumScott => self.try_resugar_strings_with(Self::resugar_strings_num_scott),
}
}

/// Converts num-scott-encoded strings ending with String/nil to a string literals.
fn resugar_strings_num_scott(&mut self) {
/// Converts encoded strings to string literals using the provided extraction function.
fn try_resugar_strings_with(&mut self, extract_fn: fn(&Term) -> Option<(char, &Term)>) {
maybe_grow(|| {
// Search for a String/cons pattern in the term and try to build a string from that point on.
// If successful, replace the term with the string.
// If not, keep as-is.

// Nil: String/nil
if let Term::Ref { nam } = self {
if nam == builtins::SNIL {
*self = Term::str("");
// Try to resugar nil or cons patterns. If unsuccessful, recurse into child terms.
if !self.try_resugar_strings_nil() && !self.try_resugar_strings_cons(extract_fn) {
for child in self.children_mut() {
child.try_resugar_strings_with(extract_fn);
}
}
// Cons: @x (x CONS_TAG <num> <str>)
if let Term::Lam { tag: Tag::Static, pat, bod } = self {
if let Pattern::Var(Some(var_lam)) = pat.as_mut() {
if let Term::App { tag: Tag::Static, fun, arg: tail } = bod.as_mut() {
if let Term::App { tag: Tag::Static, fun, arg: head } = fun.as_mut() {
if let Term::App { tag: Tag::Static, fun, arg } = fun.as_mut() {
if let Term::Var { nam: var_app } = fun.as_mut() {
if let Term::Ref { nam: Name(nam) } = arg.as_mut() {
if let Term::Num { val: Num::U24(head) } = head.as_mut() {
if var_lam == var_app && nam == builtins::SCONS_TAG_REF {
let head = char::from_u32(*head).unwrap_or(char::REPLACEMENT_CHARACTER);
if let Some(str) = build_string_num_scott(tail, head.to_string()) {
*self = Term::str(&str);
} else {
// Not a string term, keep as-is.
}
}
}
}
}
}
}
})
}

/// Attempts to resugar a nil term (String/nil) to an empty string literal.
fn try_resugar_strings_nil(&mut self) -> bool {
matches!(self, Term::Ref { nam } if nam == builtins::SNIL).then(|| *self = Term::str("")).is_some()
}

/// Attempts to resugar a cons term to a string literal.
fn try_resugar_strings_cons(&mut self, extract_fn: fn(&Term) -> Option<(char, &Term)>) -> bool {
self
.try_resugar_strings_cons_with(extract_fn)
.or_else(|| self.try_resugar_strings_cons_common())
.map(|str| *self = Term::str(&str))
.is_some()
}

/// Attempts to resugar a cons term using the provided extraction function.
fn try_resugar_strings_cons_with(&self, extract_fn: fn(&Term) -> Option<(char, &Term)>) -> Option<String> {
extract_fn(self)
.and_then(|(head_char, tail)| Self::build_strings_common(tail, head_char.to_string(), extract_fn))
}

/// Attempts to resugar a cons term using the common extraction method.
fn try_resugar_strings_cons_common(&self) -> Option<String> {
if let Term::App { tag: Tag::Static, fun, arg: tail } = self {
if let Term::App { tag: Tag::Static, fun: inner_fun, arg: head } = fun.as_ref() {
if let (Term::Ref { nam }, Term::Num { val: Num::U24(head_val) }) =
(inner_fun.as_ref(), head.as_ref())
{
if nam == builtins::SCONS {
let head_char = char::from_u32(*head_val).unwrap_or(char::REPLACEMENT_CHARACTER);
return Self::build_strings_common(tail, head_char.to_string(), Self::extract_strings_common);
}
}
}
// Cons: (String/cons <num> <str>)
if let Term::App { tag: Tag::Static, fun, arg: tail } = self {
if let Term::App { tag: Tag::Static, fun, arg: head } = fun.as_mut() {
if let Term::Ref { nam } = fun.as_mut() {
if let Term::Num { val: Num::U24(head) } = head.as_mut() {
if nam == builtins::SCONS {
let head = char::from_u32(*head).unwrap_or(char::REPLACEMENT_CHARACTER);
if let Some(str) = build_string_num_scott(tail, head.to_string()) {
*self = Term::str(&str);
} else {
// Not a string term, keep as-is.
}
}
}
}
None
}

/// Builds a string from a term structure using the provided extraction function.
fn build_strings_common(
term: &Term,
mut s: String,
extract_fn: fn(&Term) -> Option<(char, &Term)>,
) -> Option<String> {
maybe_grow(|| {
let mut current = term;
loop {
match current {
// If we reach a nil term, we've completed the string
Term::Ref { nam } if nam == builtins::SNIL => return Some(s),
_ => {
// Extract the next character and continue building the string
let (head, next) = extract_fn(current).or_else(|| Self::extract_strings_common(current))?;
s.push(head);
current = next;
}
}
}

for child in self.children_mut() {
child.resugar_strings_num_scott();
}
})
}

/// Converts scott-encoded strings ending with String/nil to a string literals.
fn resugar_strings_scott(&mut self) {
maybe_grow(|| {
// Search for a String/cons pattern in the term and try to build a string from that point on.
// If successful, replace the term with the string.
// If not, keep as-is.

// Nil: String/nil
if let Term::Ref { nam } = self {
if nam == builtins::SNIL {
*self = Term::str("");
}
}
// Cons: @* @c (c <num> <str>)
if let Term::Lam { tag: Tag::Static, pat, bod } = self {
if let Pattern::Var(None) = pat.as_mut() {
if let Term::Lam { tag: Tag::Static, pat, bod } = bod.as_mut() {
if let Pattern::Var(Some(var_lam)) = pat.as_mut() {
if let Term::App { tag: Tag::Static, fun, arg: tail } = bod.as_mut() {
if let Term::App { tag: Tag::Static, fun, arg: head } = fun.as_mut() {
if let Term::Var { nam: var_app } = fun.as_mut() {
if let Term::Num { val: Num::U24(head) } = head.as_mut() {
if var_lam == var_app {
let head = char::from_u32(*head).unwrap_or(char::REPLACEMENT_CHARACTER);
if let Some(str) = build_string_scott(tail, head.to_string()) {
*self = Term::str(&str);
} else {
// Not a string term, keep as-is.
}
}
}
/// Extracts a character and the remaining term from a Scott-encoded string term.
/// The structure of this function mimics the shape of the AST for easier visualization.
fn resugar_strings_scott(term: &Term) -> Option<(char, &Term)> {
if let Term::Lam { tag: Tag::Static, pat: outer_pat, bod } = term {
if let Pattern::Var(None) = outer_pat.as_ref() {
if let Term::Lam { tag: Tag::Static, pat: inner_pat, bod: inner_bod } = bod.as_ref() {
if let Pattern::Var(Some(var_lam)) = inner_pat.as_ref() {
if let Term::App { tag: Tag::Static, fun, arg: tail } = inner_bod.as_ref() {
if let Term::App { tag: Tag::Static, fun: inner_fun, arg: head } = fun.as_ref() {
if let (Term::Var { nam: var_app }, Term::Num { val: Num::U24(head_val) }) =
(inner_fun.as_ref(), head.as_ref())
{
if var_lam == var_app {
let head_char = char::from_u32(*head_val).unwrap_or(char::REPLACEMENT_CHARACTER);
return Some((head_char, tail));
}
}
}
}
}
}
}
// Cons: (String/cons <num> <str>)
if let Term::App { tag: Tag::Static, fun, arg: tail } = self {
if let Term::App { tag: Tag::Static, fun, arg: head } = fun.as_mut() {
if let Term::Ref { nam } = fun.as_mut() {
if let Term::Num { val: Num::U24(head) } = head.as_mut() {
if nam == builtins::SCONS {
let head = char::from_u32(*head).unwrap_or(char::REPLACEMENT_CHARACTER);
if let Some(str) = build_string_num_scott(tail, head.to_string()) {
*self = Term::str(&str);
} else {
// Not a string term, keep as-is.
}
}
}
}
}
}

for child in self.children_mut() {
child.resugar_strings_scott();
}
})
}
None
}
}

fn build_string_num_scott(term: &Term, mut s: String) -> Option<String> {
maybe_grow(|| {
// Nil: String/nil
if let Term::Ref { nam } = term {
if nam == builtins::SNIL {
return Some(s);
}
}
// Cons: @x (x CONS_TAG <num> <str>)
/// Extracts a character and the remaining term from a NumScott-encoded string term.
/// The structure of this function mimics the shape of the AST for easier visualization.
fn resugar_strings_num_scott(term: &Term) -> Option<(char, &Term)> {
if let Term::Lam { tag: Tag::Static, pat, bod } = term {
if let Pattern::Var(Some(var_lam)) = pat.as_ref() {
if let Term::App { tag: Tag::Static, fun, arg: tail } = bod.as_ref() {
if let Term::App { tag: Tag::Static, fun, arg: head } = fun.as_ref() {
if let Term::App { tag: Tag::Static, fun, arg } = fun.as_ref() {
if let Term::Var { nam: var_app } = fun.as_ref() {
if let Term::Ref { nam } = arg.as_ref() {
if let Term::Num { val: Num::U24(head) } = head.as_ref() {
if var_lam == var_app && nam == builtins::SCONS_TAG_REF {
// New string character, append and recurse
let head = char::from_u32(*head).unwrap_or(char::REPLACEMENT_CHARACTER);
s.push(head);
return build_string_num_scott(tail, s);
}
}
if let (
Term::Var { nam: var_app },
Term::Ref { nam: Name(ref_nam) },
Term::Num { val: Num::U24(head_val) },
) = (fun.as_ref(), arg.as_ref(), head.as_ref())
{
if var_lam == var_app && ref_nam == builtins::SCONS_TAG_REF {
let head_char = char::from_u32(*head_val).unwrap_or(char::REPLACEMENT_CHARACTER);
return Some((head_char, tail));
}
}
}
}
}
}
}
// Cons: (String/cons <num> <str>)
if let Term::App { tag: Tag::Static, fun, arg: tail } = term {
if let Term::App { tag: Tag::Static, fun, arg: head } = fun.as_ref() {
if let Term::Ref { nam } = fun.as_ref() {
if let Term::Num { val: Num::U24(head) } = head.as_ref() {
if nam == builtins::SCONS {
// New string character, append and recurse
let head = char::from_u32(*head).unwrap_or(char::REPLACEMENT_CHARACTER);
s.push(head);
return build_string_num_scott(tail, s);
}
}
}
}
}
// Not a string term, stop
None
})
}
}

fn build_string_scott(term: &Term, mut s: String) -> Option<String> {
maybe_grow(|| {
// Nil: String/nil
if let Term::Ref { nam } = term {
if nam == builtins::SNIL {
return Some(s);
}
}
// Cons: @* @c (c <num> <str>)
if let Term::Lam { tag: Tag::Static, pat, bod } = term {
if let Pattern::Var(None) = pat.as_ref() {
if let Term::Lam { tag: Tag::Static, pat, bod } = bod.as_ref() {
if let Pattern::Var(Some(var_lam)) = pat.as_ref() {
if let Term::App { tag: Tag::Static, fun, arg: tail } = bod.as_ref() {
if let Term::App { tag: Tag::Static, fun, arg: head } = fun.as_ref() {
if let Term::Var { nam: var_app } = fun.as_ref() {
if let Term::Num { val: Num::U24(head) } = head.as_ref() {
if var_lam == var_app {
// New string character, append and recurse
let head = char::from_u32(*head).unwrap_or(char::REPLACEMENT_CHARACTER);
s.push(head);
return build_string_scott(tail, s);
}
}
}
}
}
}
}
}
}
// Cons: (String/cons <num> <str>)
/// Extracts a character and the remaining term from a common-encoded string term.
/// The structure of this function mimics the shape of the AST for easier visualization.
fn extract_strings_common(term: &Term) -> Option<(char, &Term)> {
if let Term::App { tag: Tag::Static, fun, arg: tail } = term {
if let Term::App { tag: Tag::Static, fun, arg: head } = fun.as_ref() {
if let Term::Ref { nam } = fun.as_ref() {
if let Term::Num { val: Num::U24(head) } = head.as_ref() {
if nam == builtins::SCONS {
// New string character, append and recurse
let head = char::from_u32(*head).unwrap_or(char::REPLACEMENT_CHARACTER);
s.push(head);
return build_string_scott(tail, s);
}
if let (Term::Ref { nam }, Term::Num { val: Num::U24(head_val) }) = (fun.as_ref(), head.as_ref()) {
if nam == builtins::SCONS {
let head_char = char::from_u32(*head_val).unwrap_or(char::REPLACEMENT_CHARACTER);
return Some((head_char, tail));
}
}
}
}
// Not a string term, stop
None
})
}
}

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