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4_22.scm
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4_22.scm
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(load "ch4-analyzingmceval.scm")
(define (let? exp)
(tagged-list? exp 'let))
(define (let-bindings exp)
(cadr exp))
(define (let-body exp)
(cddr exp))
(define (analyze-let exp)
(let ((binds (let-bindings exp))
(body (let-body exp)))
(expand-let binds body)))
(define (let-vars bindings)
(map car bindings))
(define (let-values bindings)
(map cadr bindings))
(define (expand-let bindings body)
(append (list (make-lambda (let-vars bindings) body))
(let-values bindings)))
(define (analyze exp)
(cond ((self-evaluating? exp)
(analyze-self-evaluating exp))
((quoted? exp) (analyze-quoted exp))
((variable? exp) (analyze-variable exp))
((assignment? exp) (analyze-assignment exp))
((definition? exp) (analyze-definition exp))
((if? exp) (analyze-if exp))
((lambda? exp) (analyze-lambda exp))
((begin? exp) (analyze-sequence (begin-actions exp)))
((cond? exp) (analyze (cond->if exp)))
((let? exp) (analyze (analyze-let exp)))
((application? exp) (analyze-application exp))
(else
(error "Unknown expression type -- ANALYZE" exp))))
; test
;(define the-global-environment (setup-environment))
;(eval '(let ((a 1) (b 2)) (set! a 3) (+ a b)) the-global-environment)