113 lines
2.8 KiB
Scheme
113 lines
2.8 KiB
Scheme
; Copyright (c) 1993, 1994 Richard Kelsey and Jonathan Rees. See file COPYING.
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; Miniature evaluator.
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(define (eval form package)
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(evil form package))
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(define (evil exp env)
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(cond ((symbol? exp) (env exp))
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((not (pair? exp)) exp)
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((eq? (car exp) 'quote) (cadr exp))
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((eq? (car exp) 'lambda)
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(lambda args
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(evil-begin (cddr exp) (bind (cadr exp) args env))))
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((eq? (car exp) 'if)
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(evil (if (evil (cadr exp) env)
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(caddr exp)
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(cadddr exp))
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env))
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((eq? (car exp) 'define)
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(let* ((pat (cadr exp))
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(lhs (if (pair? pat) (car pat) pat))
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(rhs (if (pair? pat)
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`(lambda ,(cdr pat) ,@(cddr exp))
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(caddr exp))))
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((env '%%define%%) lhs (evil rhs env))))
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(else
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(apply (evil (car exp) env)
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(map (lambda (arg) (evil arg env)) (cdr exp))))))
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(define (evil-begin exp-list env)
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(if (null? (cdr exp-list))
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(evil (car exp-list) env)
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(begin (evil (car exp-list) env)
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(evil-begin (cdr exp-list) env))))
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(define (bind names vals env)
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(let ((alist (map cons names vals)))
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(lambda (name)
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(let ((probe (assq name alist)))
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(if probe (cdr probe) (env name))))))
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; Initial package
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(define (initial-package name)
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(let ((probe (assq name *initial-bindings*)))
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(if probe (cdr probe) (error "unbound" name))))
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(define (define-initial name val)
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(let ((probe (assq name *initial-bindings*)))
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(if probe
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(set-cdr! probe val)
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(set! *initial-bindings*
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(cons (cons name val) *initial-bindings*)))))
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(define *initial-bindings*
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(list (cons '%%define%% define-initial)))
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(define-syntax define-initial-stuff
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(syntax-rules ()
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((define-initial-stuff ?name ...)
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(for-each define-initial
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'(?name ...)
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(list ?name ...)))))
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(define-initial-stuff
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cons car cdr + - * / < = > list map append reverse
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make-vector vector-ref vector-set! vector-length
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apply)
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; LOAD
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(define (load filename)
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(load-into filename (interaction-environment)))
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(define (load-into filename env)
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(call-with-input-file filename
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(lambda (port)
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(let loop ()
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(let ((form (read port)))
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(cond ((eof-object? form))
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(else
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(eval form env)
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(loop))))))))
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(define load-quietly load-into) ; For scsh.
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(define (eval-from-file forms env filename)
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(for-each (lambda (form) (eval form env)) forms))
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(define (eval-scanned-forms forms env filename)
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(for-each (lambda (form) (eval form env)) forms))
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; Interaction environment
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(define (set-interaction-environment! package)
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(set! *interaction-environment* package))
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(define (interaction-environment)
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*interaction-environment*)
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(define *interaction-environment* initial-package)
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(define (set-scheme-report-environment! n package)
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(set! *scheme-report-environment* package))
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(define (scheme-report-environment n)
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*scheme-report-environment*)
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(define *scheme-report-environment* #f)
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