Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Common / Utils / Boolean / NegationPusher.cs / 1305376 / NegationPusher.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // // // @owner [....] // @backupOwner [....] //--------------------------------------------------------------------- using System; using System.Collections.Generic; using System.Text; using System.Diagnostics; using System.Linq; namespace System.Data.Common.Utils.Boolean { // Top-down push-down of negation in Boolean expressions. // - !(A or B) iff. !A and !B // - !(A and B) iff. !A or !B // - !!A iff. A // Uses two visitor classes: one to handle negated subtrees (essentially creates // an inverted tree) and one to handle non-negated subtrees (replicates until it // encounters NotExpr) internal static class NegationPusher { internal static BoolExpr> EliminateNot (BoolExpr > expression) { return expression.Accept(NonNegatedDomainConstraintTreeVisitor .Instance); } private class NonNegatedTreeVisitor : BasicVisitor { internal static readonly NonNegatedTreeVisitor Instance = new NonNegatedTreeVisitor (); protected NonNegatedTreeVisitor() { } internal override BoolExpr VisitNot(NotExpr expression) { return expression.Child.Accept(NegatedTreeVisitor .Instance); } } private class NegatedTreeVisitor : Visitor > { internal static readonly NegatedTreeVisitor Instance = new NegatedTreeVisitor (); protected NegatedTreeVisitor() { } internal override BoolExpr VisitTrue(TrueExpr expression) { return FalseExpr .Value; } internal override BoolExpr VisitFalse(FalseExpr expression) { return TrueExpr .Value; } internal override BoolExpr VisitTerm(TermExpr expression) { return new NotExpr (expression); } internal override BoolExpr VisitNot(NotExpr expression) { return expression.Child.Accept(NonNegatedTreeVisitor .Instance); } internal override BoolExpr VisitAnd(AndExpr expression) { return new OrExpr (expression.Children.Select(child => child.Accept(this))); } internal override BoolExpr VisitOr(OrExpr expression) { return new AndExpr (expression.Children.Select(child => child.Accept(this))); } } private class NonNegatedDomainConstraintTreeVisitor : NonNegatedTreeVisitor > { internal new static readonly NonNegatedDomainConstraintTreeVisitor Instance = new NonNegatedDomainConstraintTreeVisitor (); private NonNegatedDomainConstraintTreeVisitor() { } internal override BoolExpr > VisitNot(NotExpr > expression) { return expression.Child.Accept(NegatedDomainConstraintTreeVisitor .Instance); } } private class NegatedDomainConstraintTreeVisitor : NegatedTreeVisitor > { internal new static readonly NegatedDomainConstraintTreeVisitor Instance = new NegatedDomainConstraintTreeVisitor (); private NegatedDomainConstraintTreeVisitor() { } internal override BoolExpr > VisitNot(NotExpr > expression) { return expression.Child.Accept(NonNegatedDomainConstraintTreeVisitor .Instance); } internal override BoolExpr > VisitTerm(TermExpr > expression) { return new TermExpr >(expression.Identifier.InvertDomainConstraint()); } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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