(* Title: HOL/WF_Rel
ID: $Id$
Author: Konrad Slind
Copyright 1995 TU Munich
Derived WF relations: inverse image, lexicographic product, measure, ...
The simple relational product, in which (x',y')<(x,y) iff x'<x and y'<y, is a
subset of the lexicographic product, and therefore does not need to be defined
separately.
*)
WF_Rel = Finite +
(* actually belongs to Finite.thy *)
instance "*" :: (finite,finite) finite (finite_Prod)
consts
less_than :: "(nat*nat)set"
inv_image :: "('b * 'b)set => ('a => 'b) => ('a * 'a)set"
measure :: "('a => nat) => ('a * 'a)set"
lex_prod :: "[('a*'a)set, ('b*'b)set] => (('a*'b)*('a*'b))set"
(infixr "<*lex*>" 80)
finite_psubset :: "('a set * 'a set) set"
defs
less_than_def "less_than == trancl pred_nat"
inv_image_def "inv_image r f == {(x,y). (f(x), f(y)) : r}"
measure_def "measure == inv_image less_than"
lex_prod_def "ra <*lex*> rb == {((a,b),(a',b')) | a a' b b'.
((a,a') : ra | a=a' & (b,b') : rb)}"
(* finite proper subset*)
finite_psubset_def "finite_psubset == {(A,B). A < B & finite B}"
end