mirror of
https://github.com/kanaka/mal.git
synced 2024-11-11 00:52:44 +03:00
84 lines
2.9 KiB
Scheme
84 lines
2.9 KiB
Scheme
(import (scheme base))
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(import (scheme write))
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(import (lib util))
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(import (lib reader))
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(import (lib printer))
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(import (lib types))
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(import (lib env))
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(define (READ input)
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(read-str input))
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(define (eval-ast ast env)
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(let ((type (and (mal-object? ast) (mal-type ast)))
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(value (and (mal-object? ast) (mal-value ast))))
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(case type
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((symbol) (env-get env value))
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((list) (mal-list (map (lambda (item) (EVAL item env)) value)))
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((vector) (mal-vector (vector-map (lambda (item) (EVAL item env)) value)))
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((map) (mal-map (alist-map (lambda (key value) (cons key (EVAL value env))) value)))
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(else ast))))
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(define (EVAL ast env)
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(let ((type (and (mal-object? ast) (mal-type ast))))
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(if (not (eq? type 'list))
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(eval-ast ast env)
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(let ((items (mal-value ast)))
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(if (null? items)
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ast
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(case (mal-value (car items))
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((def!)
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(let ((symbol (mal-value (cadr items)))
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(value (EVAL (list-ref items 2) env)))
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(env-set env symbol value)
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value))
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((let*)
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(let* ((env* (make-env env))
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(binds (mal-value (cadr items)))
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(binds (if (vector? binds) (vector->list binds) binds))
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(form (list-ref items 2)))
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(let loop ((binds binds))
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(when (pair? binds)
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(let ((key (mal-value (car binds))))
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(when (null? (cdr binds))
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(error "unbalanced list"))
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(let ((value (EVAL (cadr binds) env*)))
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(env-set env* key value)
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(loop (cddr binds))))))
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(EVAL form env*)))
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(else
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(let* ((items (mal-value (eval-ast ast env)))
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(op (car items))
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(ops (cdr items)))
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(apply op ops)))))))))
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(define (PRINT ast)
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(pr-str ast #t))
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(define repl-env (make-env #f))
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(env-set repl-env '+ (lambda (a b) (mal-number (+ (mal-value a) (mal-value b)))))
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(env-set repl-env '- (lambda (a b) (mal-number (- (mal-value a) (mal-value b)))))
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(env-set repl-env '* (lambda (a b) (mal-number (* (mal-value a) (mal-value b)))))
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(env-set repl-env '/ (lambda (a b) (mal-number (/ (mal-value a) (mal-value b)))))
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(define (rep input)
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(PRINT (EVAL (READ input) repl-env)))
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(define (main)
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(let loop ()
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(let ((input (readline "user> ")))
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(when input
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(guard
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(ex ((error-object? ex)
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(when (not (memv 'empty-input (error-object-irritants ex)))
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(display "[error] ")
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(display (error-object-message ex))
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(newline))))
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(display (rep input))
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(newline))
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(loop))))
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(newline))
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(main)
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