7491e172ea
The eopl language is now racket-based rather than mzscheme-based. This test-suite, which was originally distributed on the book's web-site has been re-written in the new language. Changes include dropping all drscheme-init.scm and top.scm files. Remaining files were renamed to use the .rkt extension and edited to use the #lang syntax (instead of modulue). Require and provide forms were changed to reflect racket's syntax instead of mzscheme's (eg, only-in vs. only). Several occurrences of one-armed ifs were changed to use when and unless. All tests have been run successfully.
62 lines
1.9 KiB
Racket
Executable File
62 lines
1.9 KiB
Racket
Executable File
#lang eopl
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(require "data-structures.rkt")
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(provide init-env empty-env extend-env apply-env)
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;;;;;;;;;;;;;;;; initial environment ;;;;;;;;;;;;;;;;
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;; init-env : () -> Env
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;; usage: (init-env) = [i=1, v=5, x=10]
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;; (init-env) builds an environment in which i is bound to the
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;; expressed value 1, v is bound to the expressed value 5, and x is
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;; bound to the expressed value 10.
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;; Page: 69
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(define init-env
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(lambda ()
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(extend-env
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'i (num-val 1)
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(extend-env
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'v (num-val 5)
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(extend-env
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'x (num-val 10)
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(empty-env))))))
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;;;;;;;;;;;;;;;; environment constructors and observers ;;;;;;;;;;;;;;;;
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(define apply-env
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(lambda (env search-sym)
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(cases environment env
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(empty-env ()
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(eopl:error 'apply-env "No binding for ~s" search-sym))
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(extend-env (bvar bval saved-env)
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(if (eqv? search-sym bvar)
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bval
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(apply-env saved-env search-sym)))
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(extend-env-rec* (p-names b-vars p-bodies saved-env)
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(cond
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((location search-sym p-names)
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=> (lambda (n)
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(proc-val
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(procedure
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(list-ref b-vars n)
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(list-ref p-bodies n)
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env))))
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(else (apply-env saved-env search-sym)))))))
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;; location : Sym * Listof(Sym) -> Maybe(Int)
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;; (location sym syms) returns the location of sym in syms or #f is
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;; sym is not in syms. We can specify this as follows:
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;; if (memv sym syms)
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;; then (list-ref syms (location sym syms)) = sym
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;; else (location sym syms) = #f
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(define location
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(lambda (sym syms)
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(cond
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((null? syms) #f)
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((eqv? sym (car syms)) 0)
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((location sym (cdr syms))
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=> (lambda (n)
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(+ n 1)))
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(else #f))))
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