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24 lines
668 B
Plaintext
24 lines
668 B
Plaintext
(* Binary search
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A classical example. Searches a sorted array for a given value v.
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Consult <https://gitlab.inria.fr/why3/why3/-/blob/master/examples/binary_search.mlw>.
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*)
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module BinarySearch
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use import int.Int
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use import int.ComputerDivision
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use import ref.Ref
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use import array.Array
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let binary_search (a : array int) (v : int)
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requires { forall i1 i2 : int. 0 <= i1 < i2 < length a -> a[i1] <= a[i2] }
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ensures { 0 <= result <= length a }
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ensures { forall i: int. 0 <= i < result -> a[i] < v }
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ensures { result < length a -> a[result] >= v }
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=
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let l = ref (-1) in
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let u = ref (length a) in
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!u - !l (* TODO *)
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end
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