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(* Title: ZF/OrderArith.thy


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ID: $Id$


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Author: Lawrence C Paulson, Cambridge University Computer Laboratory


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Copyright 1994 University of Cambridge


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Towards ordinal arithmetic


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*)


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OrderArith = Order + Sum +


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consts


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radd, rmult :: "[i,i,i,i]=>i"


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rvimage :: "[i,i,i]=>i"


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rules


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(*disjoint sum of two relations; underlies ordinal addition*)


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radd_def "radd(A,r,B,s) == \


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\ {z: (A+B) * (A+B). \


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\ (EX x y. z = <Inl(x), Inr(y)>)  \


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\ (EX x' x. z = <Inl(x'), Inl(x)> & <x',x>:r)  \


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\ (EX y' y. z = <Inr(y'), Inr(y)> & <y',y>:s)}"


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(*lexicographic product of two relations; underlies ordinal multiplication*)


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rmult_def "rmult(A,r,B,s) == \


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\ {z: (A*B) * (A*B). \


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\ EX x' y' x y. z = <<x',y'>, <x,y>> & \


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\ (<x',x>: r  (x'=x & <y',y>: s))}"


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(*inverse image of a relation*)


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rvimage_def "rvimage(A,f,r) == {z: A*A. EX x y. z = <x,y> & <f`x,f`y>: r}"


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end
