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(* Title: ZF/Coind/Types.thy
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ID: $Id$
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Author: Jacob Frost, Cambridge University Computer Laboratory
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Copyright 1995 University of Cambridge
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*)
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Types = Language +
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consts
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Ty :: i (* Datatype of types *)
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TyConst :: i (* Abstract type of type constants *)
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datatype <= "univ(TyConst)"
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"Ty" = t_const("tc:TyConst")
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| t_fun("t1:Ty","t2:Ty")
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(* Definition of type environments and associated operators *)
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consts
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TyEnv :: i
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datatype <= "univ(Ty Un ExVar)"
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"TyEnv" = te_emp
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| te_owr("te:TyEnv","x:ExVar","t:Ty")
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consts
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te_dom :: i => i
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te_app :: [i,i] => i
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primrec (*domain of the type environment*)
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"te_dom (te_emp) = 0"
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"te_dom(te_owr(te,x,v)) = te_dom(te) Un {x}"
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primrec (*lookup up identifiers in the type environment*)
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"te_app (te_emp,x) = 0"
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"te_app (te_owr(te,y,t),x) = if(x=y, t, te_app(te,x))"
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end
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