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(* Title: HOL/Hoare/ExamplesAbort.thy
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ID: $Id$
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Author: Tobias Nipkow
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Copyright 1998 TUM
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Some small examples for programs that may abort.
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Currently only show the absence of abort.
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*)
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13856
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theory ExamplesAbort = HoareAbort:
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syntax guarded_com :: "'bool \<Rightarrow> 'a com \<Rightarrow> 'a com" ("_ \<rightarrow> _" 60)
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translations "P \<rightarrow> c" == "IF P THEN c ELSE Abort FI"
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lemma "VARS x y z::nat
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{y = z & z \<noteq> 0} z \<noteq> 0 \<rightarrow> x := y div z {x = 1}"
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by vcg_simp
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lemma "VARS (a::int list) i
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{True}
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i := 0;
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WHILE i < length a
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INV {i <= length a}
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DO i < length a \<rightarrow> a := a[i := 7];
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i := i+1
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OD
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{True}"
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apply vcg_simp
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apply arith
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done
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end
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