src/HOL/Univ.thy
author paulson
Mon Dec 07 18:26:25 1998 +0100 (1998-12-07)
changeset 6019 0e55c2fb2ebb
parent 5978 fa2c2dd74f8c
child 7014 11ee650edcd2
permissions -rw-r--r--
tidying
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(*  Title:      HOL/Univ.thy
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1993  University of Cambridge
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Declares the type 'a node, a subtype of (nat=>nat) * ('a+nat)
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Defines "Cartesian Product" and "Disjoint Sum" as set operations.
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Could <*> be generalized to a general summation (Sigma)?
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*)
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Univ = Arith + Sum +
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(** lists, trees will be sets of nodes **)
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global
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typedef (Node)
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  'a node = "{p. EX f x k. p = (f::nat=>nat, x::'a+nat) & f(k)=0}"
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types
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  'a item = 'a node set
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consts
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  apfst     :: "['a=>'c, 'a*'b] => 'c*'b"
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  Push      :: [nat, nat=>nat] => (nat=>nat)
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  Push_Node :: [nat, 'a node] => 'a node
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  ndepth    :: 'a node => nat
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  Atom      :: "('a+nat) => 'a item"
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  Leaf      :: 'a => 'a item
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  Numb      :: nat => 'a item
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  Scons     :: ['a item, 'a item]=> 'a item
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  In0,In1   :: 'a item => 'a item
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  ntrunc    :: [nat, 'a item] => 'a item
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  "<*>"  :: ['a item set, 'a item set]=> 'a item set (infixr 80)
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  "<+>"  :: ['a item set, 'a item set]=> 'a item set (infixr 70)
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  Split  :: [['a item, 'a item]=>'b, 'a item] => 'b
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  Case   :: [['a item]=>'b, ['a item]=>'b, 'a item] => 'b
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  "<**>" :: "[('a item * 'a item)set, ('a item * 'a item)set] 
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           => ('a item * 'a item)set" (infixr 80)
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  "<++>" :: "[('a item * 'a item)set, ('a item * 'a item)set] 
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           => ('a item * 'a item)set" (infixr 70)
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local
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defs
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  Push_Node_def  "Push_Node == (%n x. Abs_Node (apfst (Push n) (Rep_Node x)))"
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  (*crude "lists" of nats -- needed for the constructions*)
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  apfst_def  "apfst == (%f (x,y). (f(x),y))"
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  Push_def   "Push == (%b h. nat_case (Suc b) h)"
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  (** operations on S-expressions -- sets of nodes **)
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  (*S-expression constructors*)
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  Atom_def   "Atom == (%x. {Abs_Node((%k.0, x))})"
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  Scons_def  "Scons M N == (Push_Node(0) `` M) Un (Push_Node(Suc(0)) `` N)"
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  (*Leaf nodes, with arbitrary or nat labels*)
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  Leaf_def   "Leaf == Atom o Inl"
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  Numb_def   "Numb == Atom o Inr"
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  (*Injections of the "disjoint sum"*)
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  In0_def    "In0(M) == Scons (Numb 0) M"
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  In1_def    "In1(M) == Scons (Numb 1) M"
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  (*the set of nodes with depth less than k*)
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  ndepth_def "ndepth(n) == (%(f,x). LEAST k. f(k)=0) (Rep_Node n)"
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  ntrunc_def "ntrunc k N == {n. n:N & ndepth(n)<k}"
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  (*products and sums for the "universe"*)
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  uprod_def  "A<*>B == UN x:A. UN y:B. { Scons x y }"
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  usum_def   "A<+>B == In0``A Un In1``B"
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  (*the corresponding eliminators*)
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  Split_def  "Split c M == @u. ? x y. M = Scons x y & u = c x y"
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  Case_def   "Case c d M == @u.  (? x . M = In0(x) & u = c(x)) 
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                              | (? y . M = In1(y) & u = d(y))"
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  (** equality for the "universe" **)
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  dprod_def  "r<**>s == UN (x,x'):r. UN (y,y'):s. {(Scons x y, Scons x' y')}"
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  dsum_def   "r<++>s == (UN (x,x'):r. {(In0(x),In0(x'))}) Un 
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                        (UN (y,y'):s. {(In1(y),In1(y'))})"
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end