author | clasohm |
Wed, 21 Jun 1995 15:12:40 +0200 | |
changeset 249 | 492493334e0f |
parent 48 | 21291189b51e |
permissions | -rw-r--r-- |
(* Title: HOL/ex/qsort.thy ID: $Id$ Author: Tobias Nipkow Copyright 1994 TU Muenchen Quicksort *) Qsort = Sorting + consts qsort :: "[['a,'a] => bool, 'a list] => 'a list" rules qsort_Nil "qsort(le,[]) = []" qsort_Cons "qsort(le,x#xs) = qsort(le,[y:xs . ~le(x,y)]) @ (x# qsort(le,[y:xs . le(x,y)]))" (* computational induction. The dependence of p on x but not xs is intentional. *) qsort_ind "[| P([]); !!x xs. [| P([y:xs . ~p(x,y)]); P([y:xs . p(x,y)]) |] ==> P(x#xs) |] ==> P(xs)" end