(* Title: HOL/Hoare/Pointer_ExamplesAbort.thy
Author: Tobias Nipkow
Copyright 2002 TUM
Examples of verifications of pointer programs
*)
theory Pointer_ExamplesAbort imports HeapSyntaxAbort begin
section "Verifications"
subsection "List reversal"
text "Interestingly, this proof is the same as for the unguarded program:"
lemma "VARS tl p q r
{List tl p Ps \<and> List tl q Qs \<and> set Ps \<inter> set Qs = {}}
WHILE p \<noteq> Null
INV {\<exists>ps qs. List tl p ps \<and> List tl q qs \<and> set ps \<inter> set qs = {} \<and>
rev ps @ qs = rev Ps @ Qs}
DO r := p; (p \<noteq> Null \<rightarrow> p := p^.tl); r^.tl := q; q := r OD
{List tl q (rev Ps @ Qs)}"
apply vcg_simp
apply fastforce
apply(fastforce intro:notin_List_update[THEN iffD2])
apply fastforce
done
end