src/HOL/MiniML/Maybe.ML
author nipkow
Fri, 17 Jan 1997 18:32:24 +0100
changeset 2523 0ccea141409b
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child 2525 477c05586286
permissions -rw-r--r--
Updated documentation pointers.
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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";
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goal Maybe.thy
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  "((m bind f) = Fail) = ((m=Fail) | (? p. m = Ok p & f p = Fail))";
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by (simp_tac (!simpset setloop (split_tac [expand_bind])) 1);
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qed "bind_eq_Fail";
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Addsimps [bind_eq_Fail];