(* Title: Sequents/LK/Propositional.thy
Author: Lawrence C Paulson, Cambridge University Computer Laboratory
Copyright 1992 University of Cambridge
*)
section \<open>Classical sequent calculus: examples with propositional connectives\<close>
theory Propositional
imports "../LK"
begin
text "absorptive laws of \ and \"
lemma "\ P \ P \ P"
by fast_prop
lemma "\ P \ P \ P"
by fast_prop
text "commutative laws of \ and \"
lemma "\ P \ Q \ Q \ P"
by fast_prop
lemma "\ P \ Q \ Q \ P"
by fast_prop
text "associative laws of \ and \"
lemma "\ (P \ Q) \ R \ P \ (Q \ R)"
by fast_prop
lemma "\ (P \ Q) \ R \ P \ (Q \ R)"
by fast_prop
text "distributive laws of \ and \"
lemma "\ (P \ Q) \ R \ (P \ R) \ (Q \ R)"
by fast_prop
lemma "\ (P \ Q) \ R \ (P \ R) \ (Q \ R)"
by fast_prop
text "Laws involving implication"
lemma "\ (P \ Q \ R) \ (P \ R) \ (Q \ R)"
by fast_prop
lemma "\ (P \ Q \ R) \ (P \ (Q \ R))"
by fast_prop
lemma "\ (P \ Q \ R) \ (P \ Q) \ (P \ R)"
by fast_prop
text "Classical theorems"
lemma "\ P \ Q \ P \ \ P \ Q"
by fast_prop
lemma "\ (P \ Q) \ (\ P \ R) \ (P \ Q \ R)"
by fast_prop
lemma "\ P \ Q \ \ P \ R \ (P \ Q) \ (\ P \ R)"
by fast_prop
lemma "\ (P \ Q) \ (P \ R) \ (P \ Q \ R)"
by fast_prop
(*If and only if*)
lemma "\ (P \ Q) \ (Q \ P)"
by fast_prop
lemma "\ \ (P \ \ P)"
by fast_prop
(*Sample problems from
F. J. Pelletier,
Seventy-Five Problems for Testing Automatic Theorem Provers,
J. Automated Reasoning 2 (1986), 191-216.
Errata, JAR 4 (1988), 236-236.
*)
(*1*)
lemma "\ (P \ Q) \ (\ Q \ \ P)"
by fast_prop
(*2*)
lemma "\ \ \ P \ P"
by fast_prop
(*3*)
lemma "\ \ (P \ Q) \ (Q \ P)"
by fast_prop
(*4*)
lemma "\ (\ P \ Q) \ (\ Q \ P)"
by fast_prop
(*5*)
lemma "\ ((P \ Q) \ (P \ R)) \ (P \ (Q \ R))"
by fast_prop
(*6*)
lemma "\ P \ \ P"
by fast_prop
(*7*)
lemma "\ P \ \ \ \ P"
by fast_prop
(*8. Peirce's law*)
lemma "\ ((P \ Q) \ P) \ P"
by fast_prop
(*9*)
lemma "\ ((P \ Q) \ (\ P \ Q) \ (P \ \ Q)) \ \ (\ P \ \ Q)"
by fast_prop
(*10*)
lemma "Q \ R, R \ P \ Q, P \ (Q \ R) \ P \ Q"
by fast_prop
(*11. Proved in each direction (incorrectly, says Pelletier!!) *)
lemma "\ P \ P"
by fast_prop
(*12. "Dijkstra's law"*)
lemma "\ ((P \ Q) \ R) \ (P \ (Q \ R))"
by fast_prop
(*13. Distributive law*)
lemma "\ P \ (Q \ R) \ (P \ Q) \ (P \ R)"
by fast_prop
(*14*)
lemma "\ (P \ Q) \ ((Q \ \ P) \ (\ Q \ P))"
by fast_prop
(*15*)
lemma "\ (P \ Q) \ (\ P \ Q)"
by fast_prop
(*16*)
lemma "\ (P \ Q) \ (Q \ P)"
by fast_prop
(*17*)
lemma "\ ((P \ (Q \ R)) \ S) \ ((\ P \ Q \ S) \ (\ P \ \ R \ S))"
by fast_prop
end
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