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Long tut alpha equivalence #112

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Long tut alpha equivalence #112

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e318627
supply missing `in` metafunction
haroldcarr Jul 4, 2017
730e371
removed unnecessary Lambda/n - fix test to conform to SD
haroldcarr Jul 4, 2017
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13 changes: 5 additions & 8 deletions redex-doc/redex/scribblings/long-tut/mon-aft.scrbl
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Original file line number Diff line number Diff line change
Expand Up @@ -207,7 +207,10 @@ Here are two more metafunctions that use patterns in interesting ways:
(where #false (in x (x_1 ...)))]
[(subtract1 (x ...) x_1) (x ...)])


(define-metafunction Lambda
in : x (x ...) -> boolean
[(in x (x_1 ... x x_2 ...)) #true]
[(in x (x_1 ...)) #false])

))
@;%
Expand Down Expand Up @@ -319,15 +322,9 @@ Now α equivalence is straightforward:
(racketblock
;; (=α e_1 e_2) determines whether e_1 and e_2 are α equivalent

(define-extended-language Lambda/n Lambda
(e ::= .... n)
(n ::= natural))

(define in-Lambda/n? (redex-match? Lambda/n e))

(module+ test
(test-equal (term (=α (lambda (x) x) (lambda (y) y))) #true)
(test-equal (term (=α (lambda (x) (x 1)) (lambda (y) (y 1)))) #true)
(test-equal (term (=α (lambda (x) (x x)) (lambda (y) (y y)))) #true)
(test-equal (term (=α (lambda (x) x) (lambda (y) z))) #false))

(define-metafunction SD
Expand Down