Clause.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Common / Utils / Boolean / Clause.cs / 1305376 / Clause.cs
                        
                        
                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner [....]
// @backupOwner [....] 
//--------------------------------------------------------------------- 

using System; 
using System.Collections.Generic;
using System.Text;
using System.Globalization;
using System.Collections.ObjectModel; 
using System.Diagnostics;
using System.Linq; 
 
namespace System.Data.Common.Utils.Boolean
{ 
    /// 
    /// Base class for clauses, which are (constrained) combinations of literals.
    /// 
    /// Type of normal form literal. 
    internal abstract class Clause : NormalFormNode
    { 
        private readonly Set> _literals; 
        private readonly int _hashCode;
 
        /// 
        /// Initialize a new clause.
        /// 
        /// Literals contained in the clause. 
        /// Type of expression tree to produce from literals.
        protected Clause(Set> literals, ExprType treeType) 
            : base(ConvertLiteralsToExpr(literals, treeType)) 
        {
            _literals = literals.AsReadOnly(); 
            _hashCode = _literals.GetElementsHashCode();
        }

        ///  
        /// Gets the literals contained in this clause.
        ///  
        internal Set> Literals 
        {
            get { return _literals; } 
        }

        // Given a collection of literals and a tree type, returns an expression of the given type.
        private static BoolExpr ConvertLiteralsToExpr(Set> literals, ExprType treeType) 
        {
            bool isAnd = ExprType.And == treeType; 
            Debug.Assert(isAnd || ExprType.Or == treeType); 

            IEnumerable> literalExpressions = literals.Select( 
                new Func, BoolExpr>(ConvertLiteralToExpression));

            if (isAnd)
            { 
                return new AndExpr(literalExpressions);
            } 
            else 
            {
                return new OrExpr(literalExpressions); 
            }
        }

        // Given a literal, returns its logical equivalent expression. 
        private static BoolExpr ConvertLiteralToExpression(Literal literal)
        { 
            return literal.Expr; 
        }
 
        public override string ToString()
        {
            StringBuilder builder = new StringBuilder();
            builder.Append("Clause{"); 
            builder.Append(_literals);
            return builder.Append("}").ToString(); 
        } 

        public override int GetHashCode() 
        {
            return _hashCode;
        }
 
        public override bool Equals(object obj)
        { 
            Debug.Fail("call typed Equals"); 
            return base.Equals(obj);
        } 
    }

    /// 
    /// A DNF clause is of the form: 
    ///
    ///     Literal1 . Literal2 . ... 
    /// 
    /// Each literal is of the form:
    /// 
    ///     Term
    ///
    /// or
    /// 
    ///     !Term
    ///  
    /// Type of normal form literal. 
    internal sealed class DnfClause : Clause,
        IEquatable> 
    {
        /// 
        /// Initialize a DNF clause.
        ///  
        /// Literals in clause.
        internal DnfClause(Set> literals) 
            : base(literals, ExprType.And) 
        {
        } 

        public bool Equals(DnfClause other)
        {
            return null != other && 
                other.Literals.SetEquals(Literals);
        } 
    } 

    ///  
    /// A CNF clause is of the form:
    ///
    ///     Literal1 + Literal2 . ...
    /// 
    /// Each literal is of the form:
    /// 
    ///     Term 
    ///
    /// or 
    ///
    ///     !Term
    /// 
    /// Type of normal form literal. 
    internal sealed class CnfClause : Clause,
        IEquatable> 
    { 
        /// 
        /// Initialize a CNF clause. 
        /// 
        /// Literals in clause.
        internal CnfClause(Set> literals)
            : base(literals, ExprType.Or) 
        {
        } 
 
        public bool Equals(CnfClause other)
        { 
            return null != other &&
                other.Literals.SetEquals(Literals);
        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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Clause.cs source code in C# .NET

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