Mercurial > urweb
view src/order.sml @ 714:0f42461273cf
CHECK constraints
author | Adam Chlipala <adamc@hcoop.net> |
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date | Thu, 09 Apr 2009 15:30:15 -0400 |
parents | ffa18975e661 |
children |
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(* Copyright (c) 2008, Adam Chlipala * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * - Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * - Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * - The names of contributors may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. *) (* Utility code for implementing comparisons *) structure Order :> ORDER = struct fun join (o1, o2) = case o1 of EQUAL => o2 () | v => v fun joinL f (os1, os2) = case (os1, os2) of (nil, nil) => EQUAL | (nil, _) => LESS | (h1 :: t1, h2 :: t2) => join (f (h1, h2), fn () => joinL f (t1, t2)) | (_ :: _, nil) => GREATER fun joinO f (v1, v2) = case (v1, v2) of (NONE, NONE) => EQUAL | (NONE, _) => LESS | (_, NONE) => GREATER | (SOME v1, SOME v2) => f (v1, v2) end