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(* Title: Option.ML
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ID: $Id$
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Author: Tobias Nipkow
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Copyright 1994 TU Muenchen
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Derived rules
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*)
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Addsimps [Let_def];
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val [prem] = goal Option.thy "P(opt) ==> P(None) | (? x. P(Some(x)))";
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br (prem RS rev_mp) 1;
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by (Option.option.induct_tac "opt" 1);
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by (ALLGOALS(fast_tac HOL_cs));
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val optE = store_thm("optE", standard(result() RS disjE));
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goal Option.thy "x=None | (? y.x=Some(y))";
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by (Option.option.induct_tac "x" 1);
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by (Asm_full_simp_tac 1);
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by (rtac disjI2 1);
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by (rtac exI 1);
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by (Asm_full_simp_tac 1);
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qed"opt_cases";
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