src/HOL/Subst/AList.thy

added type constraint ::nat because 0 is now overloaded

(*  Title:      Subst/AList.thy
    ID:         $Id$
    Author:     Martin Coen, Cambridge University Computer Laboratory
    Copyright   1993  University of Cambridge

Association lists.
*)

AList = List + 

consts
  alist_rec  :: "[('a*'b)list, 'c, ['a, 'b, ('a*'b)list, 'c]=>'c] => 'c"
  assoc      :: "['a,'b,('a*'b) list] => 'b"

primrec
  "alist_rec [] c d = c"
  "alist_rec (p # al) c d = d (fst p) (snd p) al (alist_rec al c d)"

primrec
  "assoc v d [] = d"
  "assoc v d (p # al) = (if v = fst p then snd p else assoc v d al)"

end