src/ZF/Fixedpt.thy
author clasohm
Tue Feb 06 12:27:17 1996 +0100 (1996-02-06)
changeset 1478 2b8c2a7547ab
parent 1401 0c439768f45c
child 2469 b50b8c0eec01
permissions -rw-r--r--
expanded tabs
     1 (*  Title:      ZF/fixedpt.thy
     2     ID:         $Id$
     3     Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
     4     Copyright   1992  University of Cambridge
     5 
     6 Least and greatest fixed points
     7 *)
     8 
     9 Fixedpt = ZF + "domrange" +
    10 consts
    11   bnd_mono    :: [i,i=>i]=>o
    12   lfp, gfp    :: [i,i=>i]=>i
    13 
    14 defs
    15   (*monotone operator from Pow(D) to itself*)
    16   bnd_mono_def 
    17       "bnd_mono(D,h) == h(D)<=D & (ALL W X. W<=X --> X<=D --> h(W) <= h(X))"
    18 
    19   lfp_def     "lfp(D,h) == Inter({X: Pow(D). h(X) <= X})"
    20 
    21   gfp_def     "gfp(D,h) == Union({X: Pow(D). X <= h(X)})"
    22 
    23 end