Sentence.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Common / Utils / Boolean / Sentence.cs / 1305376 / Sentence.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
{ 
    /// 
    /// Abstract base class for nodes in normal form expressions, e.g. Conjunctive Normal Form
    /// sentences.
    ///  
    /// Type of expression leaf term identifiers.
    internal abstract class NormalFormNode 
    { 
        private readonly BoolExpr _expr;
 
        /// 
        /// Initialize a new normal form node representing the given expression. Caller must
        /// ensure the expression is logically equivalent to the node.
        ///  
        /// Expression logically equivalent to this node.
        protected NormalFormNode(BoolExpr expr) { _expr = expr.Simplify(); } 
 
        /// 
        /// Gets an expression that is logically equivalent to this node. 
        /// 
        internal BoolExpr Expr { get { return _expr; } }

        ///  
        /// Utility method for delegation that return the expression corresponding to a given
        /// normal form node. 
        ///  
        /// Type of node
        /// Node to examine. 
        /// Equivalent Boolean expression for the given node.
        protected static BoolExpr ExprSelector(T_NormalFormNode node)
            where T_NormalFormNode : NormalFormNode
        { 
            return node._expr;
        } 
    } 

    ///  
    /// Abstract base class for normal form sentences (CNF and DNF)
    /// 
    /// Type of expression leaf term identifiers.
    /// Type of clauses in the sentence. 
    internal abstract class Sentence : NormalFormNode
        where T_Clause : Clause, IEquatable 
    { 
        private readonly Set _clauses;
 
        /// 
        /// Initialize a sentence given the appropriate sentence clauses. Produces
        /// an equivalent expression by composing the clause expressions using
        /// the given tree type. 
        /// 
        /// Sentence clauses 
        /// Tree type for sentence (and generated expression) 
        protected Sentence(Set clauses, ExprType treeType)
            : base(ConvertClausesToExpr(clauses, treeType)) 
        {
            _clauses = clauses.AsReadOnly();
        }
 
        // Produces an expression equivalent to the given clauses by composing the clause
        // expressions using the given tree type. 
        private static BoolExpr ConvertClausesToExpr(Set clauses, ExprType treeType) 
        {
            bool isAnd = ExprType.And == treeType; 
            Debug.Assert(isAnd || ExprType.Or == treeType);

            IEnumerable> clauseExpressions =
                clauses.Select(new Func>(ExprSelector)); 

            if (isAnd) 
            { 
                return new AndExpr(clauseExpressions);
            } 
            else
            {
                return new OrExpr(clauseExpressions);
            } 
        }
 
        public override string ToString() 
        {
            StringBuilder builder = new StringBuilder(); 
            builder.Append("Sentence{");
            builder.Append(_clauses);
            return builder.Append("}").ToString();
        } 
    }
 
    ///  
    /// Represents a sentence in disjunctive normal form, e.g.:
    /// 
    ///     Clause1 + Clause2 . ...
    ///
    /// Where each DNF clause is of the form:
    /// 
    ///     Literal1 . Literal2 . ...
    /// 
    /// Each literal is of the form: 
    ///
    ///     Term 
    ///
    /// or
    ///
    ///     !Term 
    /// 
    /// Type of expression leaf term identifiers. 
    internal sealed class DnfSentence : Sentence> 
    {
        // Initializes a new DNF sentence given its clauses. 
        internal DnfSentence(Set> clauses)
            : base(clauses, ExprType.Or)
        {
        } 
    }
 
    ///  
    /// Represents a sentence in conjunctive normal form, e.g.:
    /// 
    ///     Clause1 . Clause2 . ...
    ///
    /// Where each DNF clause is of the form:
    /// 
    ///     Literal1 + Literal2 + ...
    /// 
    /// Each literal is of the form: 
    ///
    ///     Term 
    ///
    /// or
    ///
    ///     !Term 
    /// 
    /// Type of expression leaf term identifiers. 
    internal sealed class CnfSentence : Sentence> 
    {
        // Initializes a new CNF sentence given its clauses. 
        internal CnfSentence(Set> clauses)
            : base(clauses, ExprType.And)
        {
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

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