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(* Title: HOL/Induct/Sexp.thy
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ID: $Id$
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Author: Lawrence C Paulson, Cambridge University Computer Laboratory
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Copyright 1992 University of Cambridge
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S-expressions, general binary trees for defining recursive data
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structures by hand.
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*)
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10212
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Sexp = Datatype_Universe + Inductive +
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consts
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sexp :: 'a item set
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sexp_case :: "['a=>'b, nat=>'b, ['a item, 'a item]=>'b,
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'a item] => 'b"
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sexp_rec :: "['a item, 'a=>'b, nat=>'b,
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['a item, 'a item, 'b, 'b]=>'b] => 'b"
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pred_sexp :: "('a item * 'a item)set"
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inductive sexp
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intrs
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LeafI "Leaf(a): sexp"
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NumbI "Numb(i): sexp"
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SconsI "[| M: sexp; N: sexp |] ==> Scons M N : sexp"
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defs
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sexp_case_def
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"sexp_case c d e M == @ z. (? x. M=Leaf(x) & z=c(x))
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| (? k. M=Numb(k) & z=d(k))
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| (? N1 N2. M = Scons N1 N2 & z=e N1 N2)"
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pred_sexp_def
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"pred_sexp == UN M: sexp. UN N: sexp. {(M, Scons M N), (N, Scons M N)}"
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sexp_rec_def
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"sexp_rec M c d e == wfrec pred_sexp
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(%g. sexp_case c d (%N1 N2. e N1 N2 (g N1) (g N2))) M"
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end
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