30 lines
884 B
Scheme
30 lines
884 B
Scheme
#lang racket
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(require racket/fixnum)
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(provide explicate-control)
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(define (explicate-control sexp)
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(match sexp
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[`(program ,info ,exp)
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`(program ,info ((start . ,(explicate-control-tail exp))))]))
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; after a remove-complex-opera*, all expressions
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; are compatible with C0
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(define (explicate-control-tail exp)
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(match exp
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[(? fixnum?) `(return ,exp)]
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[(? symbol?) `(return ,exp)]
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[`(read) `(return ,exp)]
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[`(- ,e) `(return ,exp)]
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[`(+ ,e1 ,e2) `(return ,exp)]
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[`(let ([,var ,rexp]) ,body)
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(explicate-control-assign var rexp (explicate-control-tail body))]))
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; stmt := (assign var exp)
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; tail := (return exp) / (seq stmt tail)
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(define (explicate-control-assign var exp c0-body) `()
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(match exp
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[`(let ([,v ,x]) ,b) (explicate-control-assign v x (explicate-control-assign var b c0-body))]
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[_ `(seq (assign ,var ,exp) ,c0-body)]))
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