Vertex.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 / Vertex.cs / 1305376 / Vertex.cs
                        
                        
                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner [....]
// @backupOwner [....] 
//--------------------------------------------------------------------- 

using System; 
using System.Collections.Generic;

namespace System.Data.Common.Utils.Boolean
{ 
    using System.Diagnostics;
    using System.Globalization; 
 
    /// 
    /// A node in a Reduced Ordered Boolean Decision Diagram. Reads as: 
    ///
    /// if 'Variable' then 'Then' else 'Else'
    ///
    /// Invariant: the Then and Else children must refer to 'deeper' variables, 
    /// or variables with a higher value. Otherwise, the graph is not 'Ordered'.
    /// All creation of vertices is mediated by the Solver class which ensures 
    /// each vertex is unique. Otherwise, the graph is not 'Reduced'. 
    /// 
    sealed class Vertex : IEquatable 
    {
        /// 
        /// Initializes a sink BDD node (zero or one)
        ///  
        private Vertex()
        { 
            this.Variable = int.MaxValue; 
            this.Children = new Vertex[] { };
        } 

        internal Vertex(int variable, Vertex[] children)
        {
            EntityUtil.BoolExprAssert(variable < int.MaxValue, 
                "exceeded number of supported variables");
 
            AssertConstructorArgumentsValid(variable, children); 

            this.Variable = variable; 
            this.Children = children;
        }

        [Conditional("DEBUG")] 
        private static void AssertConstructorArgumentsValid(int variable, Vertex[] children)
        { 
            Debug.Assert(null != children, "internal vertices must define children"); 
            Debug.Assert(2 <= children.Length, "internal vertices must have at least two children");
            Debug.Assert(0 < variable, "internal vertices must have 0 < variable"); 
            foreach (Vertex child in children)
            {
                Debug.Assert(variable < child.Variable, "children must have greater variable");
            } 
        }
 
        ///  
        /// Sink node representing the Boolean function '1' (true)
        ///  
        internal static readonly Vertex One = new Vertex();

        /// 
        /// Sink node representing the Boolean function '0' (false) 
        /// 
        internal static readonly Vertex Zero = new Vertex(); 
 
        /// 
        /// Gets the variable tested by this vertex. If this is a sink node, returns 
        /// int.MaxValue since there is no variable to test (and since this is a leaf,
        /// this non-existent variable is 'deeper' than any existing variable; the
        /// variable value is larger than any real variable)
        ///  
        internal readonly int Variable;
 
        ///  
        /// Note: do not modify elements.
        /// Gets the result when Variable evaluates to true. If this is a sink node, 
        /// returns null.
        /// 
        internal readonly Vertex[] Children;
 
        /// 
        /// Returns true if this is '1'. 
        ///  
        internal bool IsOne()
        { 
            return object.ReferenceEquals(Vertex.One, this);
        }

        ///  
        /// Returns true if this is '0'.
        ///  
        internal bool IsZero() 
        {
            return object.ReferenceEquals(Vertex.Zero, this); 
        }

        /// 
        /// Returns true if this is '0' or '1'. 
        /// 
        internal bool IsSink() 
        { 
            return Variable == int.MaxValue;
        } 

        public bool Equals(Vertex other)
        {
            return object.ReferenceEquals(this, other); 
        }
 
        public override bool Equals(object obj) 
        {
            Debug.Fail("used typed Equals"); 
            return base.Equals(obj);
        }

        public override int GetHashCode() 
        {
            return base.GetHashCode(); 
        } 

        public override string ToString() 
        {
            if (IsOne())
            {
                return "_1_"; 
            }
            if (IsZero()) 
            { 
                return "_0_";
            } 
            return String.Format(CultureInfo.InvariantCulture, "<{0}, {1}>", Variable, StringUtil.ToCommaSeparatedString(Children));
        }
    }
} 

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

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