Created
November 11, 2008 02:22
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convert let&named-let to lambda
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;; named-letの実装復習 | |
;; let, named-let | |
;; (let name ((var1 exp1) (var2 exp2) ...) body) | |
;; -> | |
;; ((lambda (var1 var2 ...) | |
;; (define name (lambda (var1 var2 ...) body)) | |
;; (name var1 var2 ...)) | |
;; exp1 exp2 ...) | |
;; -> | |
;; ((lambda (var1 var2 ...) | |
;; ((lambda (name) body) (lambda (var1 var2 ...) body)) | |
;; body) | |
;; exp1 exp2 ...) | |
(define (make-lambda parameters body) | |
(cons 'lambda (cons parameters body))) | |
(define (named-let? exp) | |
(symbol? (cadr exp))) | |
(define (let-bindings exp) | |
(if (named-let? exp) | |
(caddr exp) | |
(cadr exp))) | |
(define (let-name exp) | |
(cadr exp)) | |
(define (let-body exp) | |
(if (named-let? exp) | |
(cdddr exp) | |
(cddr exp))) | |
(define (let-vars exp) | |
(if (null? exp) | |
'() | |
(map car (let-bindings exp)))) | |
(define (let-exps exp env) | |
(if (null? exp) | |
'() | |
(map (lambda (x) (eval (cadr x) env)) | |
(let-bindings exp)))) | |
;; let式からlambda式への変換 | |
(define (let->combination exp env) | |
(if (named-let? exp) | |
(cons (make-lambda (let-vars exp) | |
(list | |
(list 'define (let-name exp) | |
(make-lambda (let-vars exp) | |
#?=(let-body exp))) | |
(cons (let-name exp) (let-vars exp)))) | |
(let-exps exp env)) | |
(cons (make-lambda (let-vars exp) | |
(let-body exp)) | |
(let-exps exp env)))) |
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