91 lines
2.0 KiB
Racket
91 lines
2.0 KiB
Racket
#lang racket/base
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(provide (all-defined-out))
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;; expression selectors
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(define (self-evaluating? exp)
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(cond
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[(number? exp) #t]
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[(string? exp) #t]
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[else #f]))
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(define (variable? exp) (symbol? exp))
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(define (quoted? exp) (tagged-list? exp 'quote))
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(define (text-of-quotation exp) (cadr exp))
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(define (tagged-list? exp tag)
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(if (pair? exp)
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(eq? (car exp) tag)
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#f))
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(define (assignment? exp)
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(tagged-list? exp 'set!))
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(define (assignment-variable exp) (cadr exp))
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(define (assignment-value exp) (caddr exp))
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(define (definition? exp)
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(tagged-list? exp 'define))
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(define (definition-variable exp)
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(if (symbol? (cadr exp))
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(cadr exp)
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(caadr exp)))
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(define (definition-value exp)
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(if (symbol? (cadr exp))
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(caddr exp)
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(make-lambda (cdadr exp)
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(cddr exp))))
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(define (lambda? exp)
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(tagged-list? exp 'lambda))
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(define (lambda-parameters exp) (cadr exp))
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(define (lambda-body exp) (cddr exp))
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(define (make-lambda parameters body)
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(cons 'lambda (cons parameters body)))
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(define (if? exp)
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(tagged-list? exp 'if))
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(define (if-predicate exp)
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(cadr exp))
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(define (if-consequent exp)
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(caddr exp))
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(define (if-alternative exp)
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(if (not (null? (cdddr exp)))
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(cadddr exp)
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'false))
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(define (begin? exp)
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(tagged-list? exp 'begin))
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(define (begin-actions exp) (cdr exp))
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(define (last-exp? seq) (null? (cdr seq)))
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(define (first-exp seq) (car seq))
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(define (rest-exps seq) (cdr seq))
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(define (application? exp) (pair? exp))
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(define (operator exp) (car exp))
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(define (operands exp) (cdr exp))
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;; instruction sequences
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(define-struct instruction-sequence (needs modifies statements) #:transparent)
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(define empty-instruction-sequence (make-instruction-sequence '() '() '()))
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(define (make-label l)
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(gensym l))
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(define (registers-needed s)
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(if (symbol? s) '() (instruction-sequence-needs s)))
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(define (registers-modified s)
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(if (symbol? s) '() (instruction-sequence-modifies s)))
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(define (statements s)
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(if (symbol? s) (list s) (instruction-sequence-statements s)))
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