78 lines
2.4 KiB
Scheme
78 lines
2.4 KiB
Scheme
(import (chicken string))
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(define (joy stack expression dict)
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(if (null? expression)
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(values stack dict)
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(if (string? (car expression))
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(receive (s e dict0)
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(joy-eval (car expression) stack (cdr expression) dict)
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(joy s e dict0))
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(joy (cons (car expression) stack) (cdr expression) dict))))
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(define (joy-eval symbol stack expression dict)
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(values (cons symbol stack) expression dict))
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(define (string-replace str from to)
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(string-intersperse (string-split str from #t) to))
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(define (tokenize str)
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(string-split
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(string-replace (string-replace str "]" " ] ") "[" " [ ")))
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(define (tokenator token)
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(cond ((string->number token) (string->number token))
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((string=? token "true") #t)
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((string=? token "false") #f)
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(else token)))
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(define (expect-right-bracket tokens acc)
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(if (null? tokens)
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(error "Missing closing bracket.")
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(expect-right-bracket-lookahead (car tokens) (cdr tokens) acc)))
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(define (expect-right-bracket-lookahead token tokens acc)
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(cond ((string=? token "]") (values acc tokens))
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((string=? token "[")
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(receive (sub_list rest) (expect-right-bracket tokens '())
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(receive (el rrest) (expect-right-bracket rest acc)
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(values (cons sub_list el) rrest))))
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(else
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(receive (el rest) (expect-right-bracket tokens acc)
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(values (cons (tokenator token) el) rest)))))
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(define (one-token-lookahead token tokens)
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(cond ((string=? token "]") (error "Extra closing bracket."))
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((string=? token "[") (expect-right-bracket tokens '()))
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(else (values (tokenator token) tokens))))
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(define (parse0 tokens acc)
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(if (null? tokens)
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acc
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(receive (term rest_of_tokens)
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(one-token-lookahead (car tokens) (cdr tokens))
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(cons term (parse0 rest_of_tokens acc)))))
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(define (parse tokens) (parse0 tokens '()))
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(define (text-to-expression text) (parse (tokenize text)))
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(define (joy-term-to-string term)
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(cond ((boolean? term) (if term "true" "false"))
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((number? term) (->string term))
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((list? term) (conc "[" (joy-expression-to-string term) "]"))
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(else term)))
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(define (joy-expression-to-string expr)
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(string-intersperse (map joy-term-to-string expr) " "))
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(define (doit text)
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(receive (stack dict)
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(joy '() (text-to-expression text) '())
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(joy-expression-to-string stack)))
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(display (doit "ab cd [[ ]] 234 [true] false"))
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(newline)
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