Created
November 13, 2013 13:44
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EoPL Ex.2.18
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(add-load-path "../../define-datatype") | |
(load "define-datatype") | |
(define-datatype environment environment? | |
(empty-env-record) | |
(extended-env-record | |
(syms (list-of symbol?)) | |
(vals (list-of scheme-value?)) | |
(env environment?))) | |
(define scheme-value? (lambda (v) #t)) | |
(define empty-env | |
(lambda () | |
(empty-env-record))) | |
(define extend-env | |
(lambda (syms vals env) | |
(extended-env-record syms vals env))) | |
(define apply-env | |
(lambda (env sym) | |
(cases environment env | |
(empty-env-record () | |
(eopl:error 'apply-env "No binding for ~s" sym)) | |
(extended-env-record (syms vals env) | |
(let ((pos (list-find-position sym syms))) | |
(if (number? pos) | |
(list-ref vals pos) | |
(apply-env env sym))))))) | |
(define environment-to-list | |
(lambda (env) | |
(cases environment env | |
(empty-env-record () | |
'(empty-env-record)) | |
(extended-env-record (syms vals env) | |
(list 'extended-env-record syms vals (environment-to-list env)))))) |
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