Theory Pointer_ExamplesAbort

theory Pointer_ExamplesAbort
imports HeapSyntaxAbort
(*  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 ∧ List tl q Qs ∧ set Ps ∩ set Qs = {}}
WHILE p ≠ Null
INV {∃ps qs. List tl p ps ∧ List tl q qs ∧ set ps ∩ set qs = {} ∧
rev ps @ qs = rev Ps @ Qs}
DO r := p; (p ≠ Null -> 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