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theory Lemmas(* Title: HOL/IOA/NTP/Lemmas.thy ID: $Id: Lemmas.thy,v 1.6 2005/09/03 14:50:24 wenzelm Exp $ Author: Tobias Nipkow & Konrad Slind *) theory Lemmas imports Main begin end
theorem neg_flip:
(X = (¬ Y)) = ((¬ X) = Y)
theorem pred_suc:
0 < x ==> (x - 1 = y) = (x = Suc y)