(* Title: HOL/IOA/NTP/Packet.thy ID: $Id: Packet.thy,v 1.7 2007/10/21 12:21:51 wenzelm Exp $ Author: Tobias Nipkow & Konrad Slind *) theory Packet imports Multiset begin types 'msg packet = "bool * 'msg" definition hdr :: "'msg packet => bool" where "hdr == fst" definition msg :: "'msg packet => 'msg" where "msg == snd" text {* Instantiation of a tautology? *} lemma eq_packet_imp_eq_hdr: "!x. x = packet --> hdr(x) = hdr(packet)" by simp declare hdr_def [simp] msg_def [simp] end
lemma eq_packet_imp_eq_hdr:
∀x. x = packet --> hdr x = hdr packet