canonical 'cases'/'induct' rules for n-tuples (n=3..7)
(really belongs to theory Product_Type, but doesn't work there yet)
(* Title: ZF/qpair.thy
ID: $Id$
Author: Lawrence C Paulson, Cambridge University Computer Laboratory
Copyright 1993 University of Cambridge
Quine-inspired ordered pairs and disjoint sums, for non-well-founded data
structures in ZF. Does not precisely follow Quine's construction. Thanks
to Thomas Forster for suggesting this approach!
W. V. Quine, On Ordered Pairs and Relations, in Selected Logic Papers,
1966.
*)
QPair = Sum +
consts
QPair :: [i, i] => i ("<(_;/ _)>")
qfst,qsnd :: i => i
qsplit :: [[i, i] => 'a, i] => 'a::logic (*for pattern-matching*)
qconverse :: i => i
QSigma :: [i, i => i] => i
"<+>" :: [i,i]=>i (infixr 65)
QInl,QInr :: i=>i
qcase :: [i=>i, i=>i, i]=>i
syntax
"@QSUM" :: [idt, i, i] => i ("(3QSUM _:_./ _)" 10)
"<*>" :: [i, i] => i (infixr 80)
translations
"QSUM x:A. B" => "QSigma(A, %x. B)"
"A <*> B" => "QSigma(A, _K(B))"
defs
QPair_def "<a;b> == a+b"
qfst_def "qfst(p) == THE a. EX b. p=<a;b>"
qsnd_def "qsnd(p) == THE b. EX a. p=<a;b>"
qsplit_def "qsplit(c,p) == c(qfst(p), qsnd(p))"
qconverse_def "qconverse(r) == {z. w:r, EX x y. w=<x;y> & z=<y;x>}"
QSigma_def "QSigma(A,B) == UN x:A. UN y:B(x). {<x;y>}"
qsum_def "A <+> B == ({0} <*> A) Un ({1} <*> B)"
QInl_def "QInl(a) == <0;a>"
QInr_def "QInr(b) == <1;b>"
qcase_def "qcase(c,d) == qsplit(%y z. cond(y, d(z), c(z)))"
end
ML
val print_translation =
[("QSigma", dependent_tr' ("@QSUM", "op <*>"))];