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(* Title: FOL/ex/Foundation.ML
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ID: $Id$
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Author: Lawrence C Paulson, Cambridge University Computer Laboratory
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Copyright 1991 University of Cambridge
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*)
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header "Intuitionistic FOL: Examples from The Foundation of a Generic Theorem Prover"
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theory Foundation
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imports IFOL
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begin
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lemma "A&B --> (C-->A&C)"
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apply (rule impI)
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apply (rule impI)
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apply (rule conjI)
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prefer 2 apply assumption
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apply (rule conjunct1)
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apply assumption
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done
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text {*A form of conj-elimination*}
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lemma
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assumes "A & B"
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and "A ==> B ==> C"
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shows C
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apply (rule prems)
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apply (rule conjunct1)
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apply (rule prems)
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apply (rule conjunct2)
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apply (rule prems)
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done
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lemma
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assumes "!!A. ~ ~A ==> A"
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shows "B | ~B"
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apply (rule prems)
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apply (rule notI)
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apply (rule_tac P = "~B" in notE)
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apply (rule_tac [2] notI)
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apply (rule_tac [2] P = "B | ~B" in notE)
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prefer 2 apply assumption
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apply (rule_tac [2] disjI1)
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prefer 2 apply assumption
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apply (rule notI)
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apply (rule_tac P = "B | ~B" in notE)
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apply assumption
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apply (rule disjI2)
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apply assumption
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done
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lemma
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assumes "!!A. ~ ~A ==> A"
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shows "B | ~B"
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apply (rule prems)
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apply (rule notI)
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apply (rule notE)
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apply (rule_tac [2] notI)
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apply (erule_tac [2] notE)
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apply (erule_tac [2] disjI1)
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apply (rule notI)
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apply (erule notE)
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apply (erule disjI2)
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done
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lemma
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assumes "A | ~A"
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and "~ ~A"
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shows A
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apply (rule disjE)
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apply (rule prems)
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apply assumption
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apply (rule FalseE)
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apply (rule_tac P = "~A" in notE)
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apply (rule prems)
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apply assumption
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done
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subsection "Examples with quantifiers"
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lemma
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assumes "ALL z. G(z)"
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shows "ALL z. G(z)|H(z)"
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apply (rule allI)
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apply (rule disjI1)
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apply (rule prems [THEN spec])
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done
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lemma "ALL x. EX y. x=y"
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apply (rule allI)
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apply (rule exI)
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apply (rule refl)
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done
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lemma "EX y. ALL x. x=y"
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apply (rule exI)
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apply (rule allI)
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apply (rule refl)?
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oops
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text {* Parallel lifting example. *}
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lemma "EX u. ALL x. EX v. ALL y. EX w. P(u,x,v,y,w)"
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apply (rule exI allI)
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apply (rule exI allI)
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apply (rule exI allI)
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apply (rule exI allI)
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apply (rule exI allI)
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oops
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lemma
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assumes "(EX z. F(z)) & B"
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shows "EX z. F(z) & B"
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apply (rule conjE)
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apply (rule prems)
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apply (rule exE)
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apply assumption
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apply (rule exI)
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apply (rule conjI)
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apply assumption
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apply assumption
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done
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text {* A bigger demonstration of quantifiers -- not in the paper. *}
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lemma "(EX y. ALL x. Q(x,y)) --> (ALL x. EX y. Q(x,y))"
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apply (rule impI)
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apply (rule allI)
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apply (rule exE, assumption)
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apply (rule exI)
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apply (rule allE, assumption)
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apply assumption
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done
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end
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