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/*@ lemma mean_1 : \forall int x, int y; x <= y ==> x <= (x+y)/2 <= y; */
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@ n >= 0 && \valid_range(t,0,n-1) &&
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@ \forall int k1, int k2; 0 <= k1 <= k2 <= n-1 ==> t[k1] <= t[k2];
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@ (\result >= 0 && t[\result] == v) ||
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@ (\result == -1 && \forall int k; 0 <= k < n ==> t[k] != v);
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int binary_search(int* t, int n, int v) {
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int l = 0, u = n-1, p = -1;
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@ 0 <= l && u <= n-1 && -1 <= p <= n-1
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@ && (p == -1 ==> \forall int k; 0 <= k < n ==> t[k] == v ==> l <= k <= u)
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@ && (p >= 0 ==> t[p]==v);
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//@ assert l <= m <= u;
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compile-command: "PPCHOME=../.. LC_ALL=C make binary_search"