added proof of idempotence, roughly after HOL/Subst/Unify.thy
(* Title: HOL/Imperative_HOL/Imperative_HOL.thy Author: John Matthews, Galois Connections; Alexander Krauss, Lukas Bulwahn & Florian Haftmann, TU Muenchen*)header {* Entry point into monadic imperative HOL *}theory Imperative_HOLimports Array Ref Mrecbeginend