giles
036022cc17
SxRational type in OCaml (Rational of int * int, stored reduced, denom>0) and JS (SxRational class with _rational marker). n/d reader syntax in spec/parser.sx. Arithmetic contagion: int op rational → rational, rational op float → float. JS keeps int/int → float for CSS backward compatibility. OCaml as_number + safe_eq extended for cross-type rational equality so (= 2.5 5/2) → true. 62 tests in test-rationals.sx, all pass. JS: 2232 passed. OCaml: 4532 passed (+11 vs pre-fix baseline). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
611 lines
20 KiB
Plaintext
611 lines
20 KiB
Plaintext
;; ==========================================================================
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;; parser.sx — Reference SX parser specification
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;;
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;; Defines how SX source text is tokenized and parsed into AST.
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;; The parser is intentionally simple — s-expressions need minimal parsing.
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;;
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;; Single-pass recursive descent: reads source text directly into AST,
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;; no separate tokenization phase. All mutable cursor state lives inside
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;; the parse closure.
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;;
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;; Grammar:
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;; program → expr*
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;; expr → atom | list | vector | map | quote-sugar
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;; list → '(' expr* ')'
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;; vector → '[' expr* ']' (sugar for list)
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;; map → '{' (key expr)* '}'
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;; atom → string | number | rational | keyword | symbol | boolean | nil | char
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;; string → '"' (char | escape)* '"'
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;; number → '-'? digit+ ('.' digit+)? ([eE] [+-]? digit+)?
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;; rational → integer '/' digit+
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;; keyword → ':' ident
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;; symbol → ident
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;; boolean → 'true' | 'false'
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;; nil → 'nil'
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;; char → '#\' (ident | single-char)
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;; ident → ident-start ident-char*
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;; comment → ';' to end of line (discarded)
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;;
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;; Quote sugar:
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;; 'expr → (quote expr)
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;; `expr → (quasiquote expr)
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;; ,expr → (unquote expr)
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;; ,@expr → (splice-unquote expr)
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;;
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;; Reader macros:
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;; #;expr → datum comment (read and discard expr)
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;; #|raw chars| → raw string literal (no escape processing)
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;; #'expr → (quote expr)
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;; #\a → character literal (char value)
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;; #\space → named character (space = 32)
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;; #name expr → extensible dispatch (calls registered handler)
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;;
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;; Platform interface (each target implements natively):
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;; (ident-start? ch) → boolean
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;; (ident-char? ch) → boolean
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;; (make-symbol name) → Symbol value
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;; (make-keyword name) → Keyword value
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;; (escape-string s) → string with " and \ escaped for serialization
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;; (make-char n) → Char value from Unicode codepoint
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;; (make-rational n d) → Rational value (auto-reduced by GCD)
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;; (char->integer c) → Unicode codepoint of char c
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;; (char-from-code n) → single-char string from codepoint
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;; (char-code s) → codepoint of first char in string s
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;; ==========================================================================
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;; --------------------------------------------------------------------------
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;; Parser — single-pass recursive descent
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;; --------------------------------------------------------------------------
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;; Returns a list of top-level AST expressions.
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;; Parse SX source string into AST
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(define
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sx-parse
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:effects ()
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(fn
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((source :as string))
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(let
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((pos 0) (len-src (len source)))
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(define
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skip-comment
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:effects ()
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(fn
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()
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(when
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(and (< pos len-src) (not (= (nth source pos) "\n")))
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(set! pos (inc pos))
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(skip-comment))))
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(define
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skip-ws
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:effects ()
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(fn
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()
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(when
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(< pos len-src)
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(let
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((ch (nth source pos)))
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(cond
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(or (= ch " ") (= ch "\t") (= ch "\n") (= ch "\r"))
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(do (set! pos (inc pos)) (skip-ws))
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(= ch ";")
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(do (set! pos (inc pos)) (skip-comment) (skip-ws))
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:else nil)))))
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(define
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hex-digit-value
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:effects ()
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(fn (ch) (index-of "0123456789abcdef" (lower ch))))
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(define
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read-string
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:effects ()
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(fn
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()
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(set! pos (inc pos))
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(let
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((buf ""))
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(define
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read-str-loop
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:effects ()
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(fn
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()
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(if
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(>= pos len-src)
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(error "Unterminated string")
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(let
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((ch (nth source pos)))
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(cond
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(= ch "\"")
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(do (set! pos (inc pos)) nil)
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(= ch "\\")
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(do
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(set! pos (inc pos))
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(let
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((esc (nth source pos)))
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(if
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(= esc "u")
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(do
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(set! pos (inc pos))
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(let
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((d0 (hex-digit-value (nth source pos)))
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(_ (set! pos (inc pos)))
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(d1 (hex-digit-value (nth source pos)))
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(_ (set! pos (inc pos)))
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(d2 (hex-digit-value (nth source pos)))
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(_ (set! pos (inc pos)))
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(d3 (hex-digit-value (nth source pos)))
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(_ (set! pos (inc pos))))
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(set!
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buf
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(str
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buf
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(char-from-code
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(+
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(* d0 4096)
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(* d1 256)
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(* d2 16)
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d3))))
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(read-str-loop)))
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(do
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(set!
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buf
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(str
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buf
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(cond
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(= esc "n")
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"\n"
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(= esc "t")
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"\t"
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(= esc "r")
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"\r"
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:else esc)))
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(set! pos (inc pos))
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(read-str-loop)))))
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:else (do
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(set! buf (str buf ch))
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(set! pos (inc pos))
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(read-str-loop)))))))
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(read-str-loop)
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buf)))
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(define
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read-ident
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:effects ()
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(fn
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()
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(let
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((start pos))
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(define
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read-ident-loop
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:effects ()
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(fn
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()
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(when
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(and (< pos len-src) (ident-char? (nth source pos)))
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(set! pos (inc pos))
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(read-ident-loop))))
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(read-ident-loop)
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(slice source start pos))))
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(define
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read-keyword
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:effects ()
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(fn () (set! pos (inc pos)) (make-keyword (read-ident))))
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(define
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read-number
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:effects ()
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(fn
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()
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(let
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((start pos))
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(when
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(and (< pos len-src) (= (nth source pos) "-"))
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(set! pos (inc pos)))
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(define
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read-digits
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:effects ()
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(fn
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()
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(when
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(and
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(< pos len-src)
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(let
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((c (nth source pos)))
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(and (>= c "0") (<= c "9"))))
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(set! pos (inc pos))
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(read-digits))))
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(read-digits)
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(if
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(and
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(< pos len-src)
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(= (nth source pos) "/")
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(< (inc pos) len-src)
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(let
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((nc (nth source (inc pos))))
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(and (>= nc "0") (<= nc "9"))))
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(let
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((numer (parse-number (slice source start pos))))
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(set! pos (inc pos))
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(let
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((denom-start pos))
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(read-digits)
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(make-rational
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numer
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(parse-number (slice source denom-start pos)))))
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(do
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(when
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(and (< pos len-src) (= (nth source pos) "."))
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(set! pos (inc pos))
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(read-digits))
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(when
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(and
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(< pos len-src)
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(or (= (nth source pos) "e") (= (nth source pos) "E")))
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(set! pos (inc pos))
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(when
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(and
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(< pos len-src)
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(or
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(= (nth source pos) "+")
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(= (nth source pos) "-")))
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(set! pos (inc pos)))
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(read-digits))
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(parse-number (slice source start pos)))))))
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(define
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read-symbol
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:effects ()
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(fn
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()
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(let
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((name (read-ident)))
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(cond
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(= name "true")
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true
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(= name "false")
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false
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(= name "nil")
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nil
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:else (make-symbol name)))))
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(define
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read-list
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:effects ()
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(fn
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((close-ch :as string))
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(let
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((items (list)))
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(define
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read-list-loop
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:effects ()
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(fn
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()
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(skip-ws)
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(if
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(>= pos len-src)
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(error "Unterminated list")
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(if
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(= (nth source pos) close-ch)
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(do (set! pos (inc pos)) nil)
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(do (append! items (read-expr)) (read-list-loop))))))
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(read-list-loop)
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items)))
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(define
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read-map
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:effects ()
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(fn
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()
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(let
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((result (dict)))
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(define
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read-map-loop
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:effects ()
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(fn
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()
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(skip-ws)
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(if
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(>= pos len-src)
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(error "Unterminated map")
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(if
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(= (nth source pos) "}")
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(do (set! pos (inc pos)) nil)
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(let
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((key-expr (read-expr))
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(key-str
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(if
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(= (type-of key-expr) "keyword")
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(keyword-name key-expr)
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(str key-expr)))
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(val-expr (read-expr)))
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(dict-set! result key-str val-expr)
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(read-map-loop))))))
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(read-map-loop)
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result)))
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(define
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read-raw-string
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:effects ()
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(fn
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()
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(let
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((buf ""))
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(define
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raw-loop
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:effects ()
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(fn
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()
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(if
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(>= pos len-src)
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(error "Unterminated raw string")
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(let
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((ch (nth source pos)))
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(if
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(= ch "|")
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(do (set! pos (inc pos)) nil)
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(do
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(set! buf (str buf ch))
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(set! pos (inc pos))
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(raw-loop)))))))
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(raw-loop)
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buf)))
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(define
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read-char-literal
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:effects ()
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(fn
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()
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(if
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(>= pos len-src)
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(error "Unexpected end of input after #\\")
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(let
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((first-ch (nth source pos)))
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(if
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(ident-start? first-ch)
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(let
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((char-start pos))
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(define
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read-char-name-loop
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:effects ()
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(fn
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()
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(when
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(and (< pos len-src) (ident-char? (nth source pos)))
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(set! pos (inc pos))
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(read-char-name-loop))))
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(read-char-name-loop)
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(let
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((char-name (slice source char-start pos)))
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(make-char
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(cond
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(= char-name "space")
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32
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(= char-name "newline")
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10
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(= char-name "tab")
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9
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(= char-name "nul")
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0
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(= char-name "null")
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0
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(= char-name "return")
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13
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(= char-name "escape")
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27
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(= char-name "delete")
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127
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(= char-name "backspace")
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8
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(= char-name "altmode")
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27
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(= char-name "rubout")
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127
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:else (char-code first-ch)))))
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(do (set! pos (inc pos)) (make-char (char-code first-ch))))))))
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(define
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read-expr
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:effects ()
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(fn
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()
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(skip-ws)
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(if
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(>= pos len-src)
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(error "Unexpected end of input")
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(let
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((ch (nth source pos)))
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(cond
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(= ch "(")
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(do (set! pos (inc pos)) (read-list ")"))
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(= ch "[")
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(do (set! pos (inc pos)) (read-list "]"))
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(= ch "{")
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(do (set! pos (inc pos)) (read-map))
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(= ch "\"")
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(read-string)
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(= ch ":")
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(read-keyword)
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(= ch "'")
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(do
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(set! pos (inc pos))
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(list (make-symbol "quote") (read-expr)))
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(= ch "`")
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(do
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(set! pos (inc pos))
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(list (make-symbol "quasiquote") (read-expr)))
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(= ch ",")
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(do
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(set! pos (inc pos))
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(if
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(and (< pos len-src) (= (nth source pos) "@"))
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(do
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(set! pos (inc pos))
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(list (make-symbol "splice-unquote") (read-expr)))
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(list (make-symbol "unquote") (read-expr))))
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(= ch "#")
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(do
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(set! pos (inc pos))
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(if
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(>= pos len-src)
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(error "Unexpected end of input after #")
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(let
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((dispatch-ch (nth source pos)))
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(cond
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(= dispatch-ch ";")
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(do (set! pos (inc pos)) (read-expr) (read-expr))
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(= dispatch-ch "|")
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(do (set! pos (inc pos)) (read-raw-string))
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(= dispatch-ch "'")
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(do
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(set! pos (inc pos))
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(list (make-symbol "quote") (read-expr)))
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(= dispatch-ch "\\")
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(do (set! pos (inc pos)) (read-char-literal))
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(ident-start? dispatch-ch)
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(let
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((macro-name (read-ident)))
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(let
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((handler (reader-macro-get macro-name)))
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(if
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handler
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(handler (read-expr))
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(error
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(str "Unknown reader macro: #" macro-name)))))
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:else (error (str "Unknown reader macro: #" dispatch-ch))))))
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(or
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(and (>= ch "0") (<= ch "9"))
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(and
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(= ch "-")
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(< (inc pos) len-src)
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(let
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((next-ch (nth source (inc pos))))
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(and (>= next-ch "0") (<= next-ch "9")))))
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(read-number)
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(and
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(= ch ".")
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(< (+ pos 2) len-src)
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(= (nth source (+ pos 1)) ".")
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(= (nth source (+ pos 2)) "."))
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(do (set! pos (+ pos 3)) (make-symbol "..."))
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(ident-start? ch)
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(read-symbol)
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:else (error (str "Unexpected character: " ch)))))))
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(let
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((exprs (list)))
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(define
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parse-loop
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:effects ()
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(fn
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()
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(skip-ws)
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(when (< pos len-src) (append! exprs (read-expr)) (parse-loop))))
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(parse-loop)
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exprs))))
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;; --------------------------------------------------------------------------
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;; Serializer — AST → SX source text
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;; --------------------------------------------------------------------------
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;; Serialize AST value back to SX source
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(define
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sx-serialize
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:effects ()
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(fn
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(val)
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(case
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(type-of val)
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"nil"
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"nil"
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"boolean"
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(if val "true" "false")
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"number"
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(str val)
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"rational"
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(str (numerator val) "/" (denominator val))
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"string"
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(str "\"" (escape-string val) "\"")
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"symbol"
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(symbol-name val)
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"keyword"
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(str ":" (keyword-name val))
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"list"
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(str "(" (join " " (map sx-serialize val)) ")")
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"dict"
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(sx-serialize-dict val)
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"sx-expr"
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(sx-expr-source val)
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"spread"
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(str "(make-spread " (sx-serialize-dict (spread-attrs val)) ")")
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"char"
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(let
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((n (char->integer val)))
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(str
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"#\\"
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(cond
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(= n 32)
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"space"
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(= n 10)
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"newline"
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(= n 9)
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"tab"
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(= n 13)
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"return"
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(= n 0)
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"nul"
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(= n 27)
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"escape"
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(= n 127)
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"delete"
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(= n 8)
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"backspace"
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:else (char-from-code n))))
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:else (str val))))
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;; Serialize a dict to SX {:key val} format
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(define
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sx-serialize-dict
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:effects ()
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(fn
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((d :as dict))
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(str
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"{"
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(join
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" "
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(reduce
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(fn
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((acc :as list) (key :as string))
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(concat
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acc
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(list (str ":" key) (sx-serialize (dict-get d key)))))
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(list)
|
|
(keys d)))
|
|
"}")))
|
|
|
|
|
|
;; Alias: adapters use (serialize val) — canonicalize to sx-serialize
|
|
(define serialize sx-serialize)
|
|
|
|
|
|
;; --------------------------------------------------------------------------
|
|
;; Platform parser interface
|
|
;; --------------------------------------------------------------------------
|
|
;;
|
|
;; Character classification (implemented natively per target):
|
|
;; (ident-start? ch) → boolean
|
|
;; True for: a-z A-Z _ ~ * + - > < = / ! ? &
|
|
;;
|
|
;; (ident-char? ch) → boolean
|
|
;; True for: ident-start chars plus: 0-9 . : / # ,
|
|
;;
|
|
;; Constructors (provided by the SX runtime):
|
|
;; (make-symbol name) → Symbol value
|
|
;; (make-keyword name) → Keyword value
|
|
;; (parse-number s) → number (int or float from string)
|
|
;; (make-char n) → Char value from Unicode codepoint n
|
|
;; (make-rational n d) → Rational value (auto-reduced by GCD; d=0 is an error)
|
|
;; (char->integer c) → Unicode codepoint of char c
|
|
;;
|
|
;; String utilities:
|
|
;; (escape-string s) → string with " and \ escaped
|
|
;; (sx-expr-source e) → unwrap SxExpr to its source string
|
|
;; (char-from-code n) → single-char string from codepoint n
|
|
;; (char-code s) → codepoint of first char in string s
|
|
;;
|
|
;; Reader macro registry:
|
|
;; (reader-macro-get name) → handler fn or nil
|
|
;; (reader-macro-set! name handler) → register a reader macro
|
|
;; --------------------------------------------------------------------------
|