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(* Title: Relation.ML
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ID: $Id$
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Authors: Riccardo Mattolini, Dip. Sistemi e Informatica
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Lawrence C Paulson, Cambridge University Computer Laboratory
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Copyright 1994 Universita' di Firenze
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Copyright 1993 University of Cambridge
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Functions represented as relations in HOL Set Theory
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*)
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val RSLIST = curry (op MRS);
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open Relation;
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goalw Relation.thy [converse_def] "!!a b r. <a,b>:r ==> <b,a>:converse(r)";
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by (simp_tac prod_ss 1);
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by (fast_tac set_cs 1);
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qed "converseI";
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goalw Relation.thy [converse_def] "!!a b r. <a,b> : converse(r) ==> <b,a> : r";
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by (fast_tac comp_cs 1);
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qed "converseD";
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qed_goalw "converseE" Relation.thy [converse_def]
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"[| yx : converse(r); \
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\ !!x y. [| yx=<y,x>; <x,y>:r |] ==> P \
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\ |] ==> P"
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(fn [major,minor]=>
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[ (rtac (major RS CollectE) 1),
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(REPEAT (eresolve_tac [bexE,exE, conjE, minor] 1)),
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(hyp_subst_tac 1),
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(assume_tac 1) ]);
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val converse_cs = comp_cs addSIs [converseI]
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addSEs [converseD,converseE];
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qed_goalw "Domain_iff" Relation.thy [Domain_def]
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"a: Domain(r) = (EX y. <a,y>: r)"
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(fn _=> [ (fast_tac comp_cs 1) ]);
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qed_goal "DomainI" Relation.thy "!!a b r. <a,b>: r ==> a: Domain(r)"
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(fn _ => [ (etac (exI RS (Domain_iff RS iffD2)) 1) ]);
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qed_goal "DomainE" Relation.thy
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"[| a : Domain(r); !!y. <a,y>: r ==> P |] ==> P"
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(fn prems=>
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[ (rtac (Domain_iff RS iffD1 RS exE) 1),
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(REPEAT (ares_tac prems 1)) ]);
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qed_goalw "RangeI" Relation.thy [Range_def] "!!a b r.<a,b>: r ==> b : Range(r)"
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(fn _ => [ (etac (converseI RS DomainI) 1) ]);
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qed_goalw "RangeE" Relation.thy [Range_def]
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"[| b : Range(r); !!x. <x,b>: r ==> P |] ==> P"
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(fn major::prems=>
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[ (rtac (major RS DomainE) 1),
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(resolve_tac prems 1),
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(etac converseD 1) ]);
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(*** Image of a set under a function/relation ***)
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qed_goalw "Image_iff" Relation.thy [Image_def]
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"b : r^^A = (? x:A. <x,b>:r)"
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(fn _ => [ fast_tac (comp_cs addIs [RangeI]) 1 ]);
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qed_goal "Image_singleton_iff" Relation.thy
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"(b : r^^{a}) = (<a,b>:r)"
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(fn _ => [ rtac (Image_iff RS trans) 1,
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fast_tac comp_cs 1 ]);
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qed_goalw "ImageI" Relation.thy [Image_def]
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"!!a b r. [| <a,b>: r; a:A |] ==> b : r^^A"
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(fn _ => [ (REPEAT (ares_tac [CollectI,RangeI,bexI] 1)),
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(resolve_tac [conjI ] 1),
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(resolve_tac [RangeI] 1),
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(REPEAT (fast_tac set_cs 1))]);
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qed_goalw "ImageE" Relation.thy [Image_def]
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"[| b: r^^A; !!x.[| <x,b>: r; x:A |] ==> P |] ==> P"
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(fn major::prems=>
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[ (rtac (major RS CollectE) 1),
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(safe_tac set_cs),
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(etac RangeE 1),
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(rtac (hd prems) 1),
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(REPEAT (etac bexE 1 ORELSE ares_tac prems 1)) ]);
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qed_goal "Image_subset" Relation.thy
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"!!A B r. r <= Sigma(A,%x.B) ==> r^^C <= B"
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(fn _ =>
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[ (rtac subsetI 1),
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(REPEAT (eresolve_tac [asm_rl, ImageE, subsetD RS SigmaD2] 1)) ]);
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val rel_cs = converse_cs addSIs [converseI]
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addIs [ImageI, DomainI, RangeI]
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addSEs [ImageE, DomainE, RangeE];
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val rel_eq_cs = rel_cs addSIs [equalityI];
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