Theory Sorting

(*  Title:      HOL/ex/sorting.thy
    ID:         $Id: Sorting.thy,v 1.11 2005/04/22 15:32:03 paulson Exp $
    Author:     Tobias Nipkow
    Copyright   1994 TU Muenchen
*)

header{*Sorting: Basic Theory*}

theory Sorting
imports Main Multiset
begin

consts
  sorted1:: "('a => 'a => bool) => 'a list => bool"
  sorted :: "('a => 'a => bool) => 'a list => bool"

primrec
  "sorted1 le [] = True"
  "sorted1 le (x#xs) = ((case xs of [] => True | y#ys => le x y) &
                        sorted1 le xs)"

primrec
  "sorted le [] = True"
  "sorted le (x#xs) = ((∀y ∈ set xs. le x y) & sorted le xs)"


constdefs
  total  :: "('a => 'a => bool) => bool"
   "total r == (∀x y. r x y | r y x)"
  
  transf :: "('a => 'a => bool) => bool"
   "transf f == (∀x y z. f x y & f y z --> f x z)"



(* Equivalence of two definitions of `sorted' *)

lemma sorted1_is_sorted: "transf(le) ==> sorted1 le xs = sorted le xs";
apply(induct xs)
 apply simp
apply(simp split: list.split)
apply(unfold transf_def);
apply(blast)
done

lemma sorted_append [simp]:
 "sorted le (xs@ys) = 
  (sorted le xs & sorted le ys & (∀x ∈ set xs. ∀y ∈ set ys. le x y))"
by (induct xs, auto)

end