56 lines
1.7 KiB
Plaintext
56 lines
1.7 KiB
Plaintext
; Fieldtest — canonical-type-names, axis 4: canonical happy path.
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;
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; Reduce a list of Int to a 'sign profile': for each element, print
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; -1, 0, or +1 according to its compare-to-zero result. Exercises:
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; - cross-module reference to prelude.Ordering at use site
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; - pattern match against prelude.Ordering's three constructors LT/EQ/GT
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; - returning a freshly chosen Int from each arm
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; - simple recursion over a local List ADT
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;
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; Expected stdout (one per line):
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; -1 ; signum -3
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; 0 ; signum 0
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; 1 ; signum 7
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; -1 ; signum -1
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; 1 ; signum 2
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(module ct_1_ordering_signum
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(data IntList
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(doc "Local Int-list ADT; nothing fancy.")
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(ctor INil)
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(ctor ICons (con Int) (con IntList)))
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(fn signum
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(doc "Map an Int to -1/0/+1 via prelude.compare. Returns the sign as an Int.")
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(type (fn-type (params (con Int)) (ret (con Int))))
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(params n)
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(body
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(match (app compare n 0)
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(case (pat-ctor LT) (app - 0 1))
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(case (pat-ctor EQ) 0)
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(case (pat-ctor GT) 1))))
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(fn drain
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(doc "Print signum of every element of xs, in list order.")
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(type (fn-type (params (con IntList)) (ret (con Unit)) (effects IO)))
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(params xs)
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(body
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(match xs
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(case (pat-ctor INil) (lit-unit))
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(case (pat-ctor ICons h t)
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(seq (do io/print_int (app signum h))
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(tail-app drain t))))))
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(fn main
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(type (fn-type (params) (ret (con Unit)) (effects IO)))
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(params)
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(body
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(app drain
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(term-ctor IntList ICons (app - 0 3)
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(term-ctor IntList ICons 0
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(term-ctor IntList ICons 7
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(term-ctor IntList ICons (app - 0 1)
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(term-ctor IntList ICons 2
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(term-ctor IntList INil))))))))))
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