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2019
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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 1996 TU Muenchen
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Derived rules
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*)
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open Option;
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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.induct_tac "opt" 1);
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by (ALLGOALS(Fast_tac));
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bind_thm("optionE", standard(result() RS disjE));
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(*
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goal Option.thy "opt=None | (? x.opt=Some(x))";
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by (option.induct_tac "opt" 1);
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by (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"option_cases";
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*)
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goal Option.thy "P(case opt of None => a | Some(x) => b(x)) = \
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\ ((opt = None --> P a) & (!x. opt = Some x --> P(b(x))))";
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by (option.induct_tac "opt" 1);
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by (Simp_tac 1);
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by (Asm_full_simp_tac 1);
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qed"expand_option_case";
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