112 lines
3.7 KiB
Scheme
112 lines
3.7 KiB
Scheme
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(module lisp (run-lisp)
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(import scheme)
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(import chicken.base)
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(import matchable)
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(import srfi-1)
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(import util)
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(define (any-or fn ln thunk)
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(let loop ((ln ln))
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(if (null? ln)
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(thunk)
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(let ((result (fn (car ln))))
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(if result
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result
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(loop (cdr ln)))))))
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(define (run-lisp body)
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(define (lisp body environments lisp-exit)
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(define (reference symbol)
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(cdr (any-or (curry assoc symbol) (cons lisp-builtins environments) (thunk (lisp-exit (string-append "Undefined reference: " (symbol->string symbol)))))))
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(define (lisp-apply function args)
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(cond ((procedure? function)
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(apply function args))
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((list? function)
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(let ((function-arguments (car function))
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(function-body (cdr function)))
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(lisp function-body (cons (if (= (length function-arguments) (length args))
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(map cons function-arguments args)
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(lisp-exit "Wrong number of arguments to function")) environments) lisp-exit)))
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(else (lisp-exit "attempt to call atom"))))
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(define (lisp-eval body)
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(cond ((symbol? body) (reference body))
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((atom? body) body)
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((list? body) (lisp-apply (lisp-eval (car body)) (cdr body)))
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(else (lisp-exit "Unknown value type in evaluation."))))
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(define (bind name value)
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(set! environments (cons (let loop ((environment (car environments)))
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(if (null? environment)
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(list (cons name value))
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(if (eq? name (caar environment))
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(cons (cons name value) (cdr environment))
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(cons (car environment) (loop (cdr environment))))))
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(cdr environments))))
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(define lisp-builtins
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`((test . ,(lambda function-args
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(display "test function called")
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(newline)))
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(if . ,(lambda function-args
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(match function-args
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((e x y) (if (lisp-eval e)
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(lisp-eval x)
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(lisp-eval y)))
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(_ (lisp-exit "malformed if expression")))))
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(quote . ,(lambda function-args
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(match function-args
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((v) v)
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(_ (lisp-exit "malformed quote expression")))))
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(cons . ,(lambda function-args
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(match function-args
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((a b) (cons (lisp-eval a) (lisp-eval b)))
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(_ (lisp-exit "malformed cons expression")))))
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(car . ,(lambda function-args
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(match function-args
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((a) (let ((e (lisp-eval a)))
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(if (atom? e)
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(lisp-exit "tried to take car of atom")
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(car e))))
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(_ (lisp-exit "malformed car expression")))))
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(cdr . ,(lambda function-args
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(match function-args
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((a) (let ((e (lisp-eval a)))
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(if (atom? e)
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(lisp-exit "tried to take cdr of atom")
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(cdr e))))
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(_ (lisp-exit "malformed cdr expression")))))
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(atom . ,(lambda function-args
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(match function-args
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((a) (let ((e (lisp-eval a)))
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(atom? e)))
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(_ (lisp-exit "malformed atom expression")))))
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(eq . ,(lambda function-args
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(match function-args
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((a b) (let ((ea (eval a))
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(eb (eval b)))
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(equal? ea eb)))
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(_ (lisp-exit "malformed eq expression")))))
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(set . ,(lambda function-args
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(match function-args
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((a b) (let ((eb (eval b)))
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(if (symbol? a)
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(bind a b)
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(lisp-exit "tried to bind to non-symbol"))))
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(_ (lisp-exit "malformed set expression")))))
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(lambda . ,(lambda function-args
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(match function-args
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((args exp . exps)
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(if (and (list? args) (every symbol? args))
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(append (list args exp) exps)
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(lisp-exit "malformed lambda expression")))
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(_ (lisp-exit "malformed lambda expression")))))))
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(lisp-eval body))
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(call/cc (lambda (lisp-exit)
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(cons #t (lisp body (list (list)) (compose lisp-exit (curry cons #f))))))))
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