src/HOL/MiniML/Maybe.ML
author nipkow
Mon, 11 Dec 1995 11:24:51 +0100
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open Maybe;
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(* constructor laws for bind *)
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goalw thy [bind_def] "(Ok s) bind f = (f s)";
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by (Simp_tac 1);
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qed "bind_Ok";
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goalw thy [bind_def] "Fail bind f = Fail";
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by (Simp_tac 1);
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qed "bind_Fail";
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Addsimps [bind_Ok,bind_Fail];
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(* expansion of bind *)
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goal thy
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  "P(res bind f) = ((res = Fail --> P Fail) & (!s. res = Ok s --> P(f s)))";
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by (maybe.induct_tac "res" 1);
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by (fast_tac (HOL_cs addss !simpset) 1);
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by (Asm_simp_tac 1);
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qed "expand_bind";