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Added length function

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William J. Bowman 2016-01-19 11:10:58 -05:00
parent b0a5f3fc09
commit 3a644fae90
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1 changed files with 9 additions and 1 deletions
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10
cur-lib/cur/stdlib/list.rkt
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@ -8,7 +8,8 @@
List List
nil nil
cons cons
list-ref) list-ref
length)
(data List : (-> (A : Type) Type) (data List : (-> (A : Type) Type)
(nil : (-> (A : Type) (List A))) (nil : (-> (A : Type) (List A)))
@ -23,3 +24,10 @@
[z (some A a)] [z (some A a)]
[(s (n-1 : Nat)) [(s (n-1 : Nat))
((recur rest) n-1)]))])) ((recur rest) n-1)]))]))
(define (length (A : Type) (ls : (List A)))
(match ls
[(nil (A : Type))
z]
[(cons (A : Type) (a : A) (rest : (List A)))
(s (recur rest))]))