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//---------------------------------------------------------------------
// <copyright file="DomainConstraint.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
namespace System.Data.Common.Utils.Boolean
{
/// <summary>
/// Represents a variable with finite domain, e.g., c in {1, 2, 3}
/// </summary>
/// <typeparam name="T_Element">Type of domain variables (int in the above example).</typeparam>
/// <typeparam name="T_Variable">Type of the identifier (c above -- it need not be int).</typeparam>
internal class DomainVariable<T_Variable, T_Element>
{
private readonly T_Variable _identifier;
private readonly Set<T_Element> _domain;
private readonly int _hashCode;
private readonly IEqualityComparer<T_Variable> _identifierComparer;
/// <summary>
/// Constructs a new domain variable.
/// </summary>
/// <param name="identifier">Identifier </param>
/// <param name="domain">Domain of variable.</param>
/// <param name="identifierComparer">Comparer of identifier</param>
internal DomainVariable(T_Variable identifier, Set<T_Element> domain, IEqualityComparer<T_Variable> identifierComparer)
{
Debug.Assert(null != identifier && null != domain);
_identifier = identifier;
_domain = domain.AsReadOnly();
_identifierComparer = identifierComparer ?? EqualityComparer<T_Variable>.Default;
int domainHashCode = _domain.GetElementsHashCode();
int identifierHashCode = _identifierComparer.GetHashCode(_identifier);
_hashCode = domainHashCode ^ identifierHashCode;
}
internal DomainVariable(T_Variable identifier, Set<T_Element> domain) : this(identifier, domain, null) { }
/// <summary>
/// Gets the variable.
/// </summary>
internal T_Variable Identifier { get { return _identifier; } }
/// <summary>
/// Gets the domain of this variable.
/// </summary>
internal Set<T_Element> Domain { get { return _domain; } }
public override int GetHashCode()
{
return _hashCode;
}
public override bool Equals(object obj)
{
if (Object.ReferenceEquals(this, obj)) { return true; }
DomainVariable<T_Variable, T_Element> other = obj as DomainVariable<T_Variable, T_Element>;
if (null == other) { return false; }
if (_hashCode != other._hashCode) { return false; }
return (_identifierComparer.Equals(_identifier, other._identifier) && _domain.SetEquals(other._domain));
}
public override string ToString()
{
return StringUtil.FormatInvariant("{0}{{{1}}}",
_identifier.ToString(), _domain);
}
}
/// <summary>
/// Represents a constraint of the form:
///
/// Var1 in Range
/// </summary>
/// <typeparam name="T_Element">Type of range elements.</typeparam>
/// <typeparam name="T_Variable">Type of the variable.</typeparam>
internal class DomainConstraint<T_Variable, T_Element>
{
private readonly DomainVariable<T_Variable, T_Element> _variable;
private readonly Set<T_Element> _range;
private readonly int _hashCode;
/// <summary>
/// Constructs a new constraint for the given variable and range.
/// </summary>
/// <param name="variable">Variable in constraint.</param>
/// <param name="range">Range of constraint.</param>
internal DomainConstraint(DomainVariable<T_Variable, T_Element> variable, Set<T_Element> range)
{
Debug.Assert(null != variable && null != range);
_variable = variable;
_range = range.AsReadOnly();
_hashCode = _variable.GetHashCode() ^ _range.GetElementsHashCode();
}
/// <summary>
/// Constructor supporting a singleton range domain constraint
/// </summary>
internal DomainConstraint(DomainVariable<T_Variable, T_Element> variable, T_Element element)
: this(variable, new Set<T_Element>(new T_Element[] { element }).MakeReadOnly())
{
}
/// <summary>
/// Gets the variable for this constraint.
/// </summary>
internal DomainVariable<T_Variable, T_Element> Variable { get { return _variable; } }
/// <summary>
/// Get the range for this constraint.
/// </summary>
internal Set<T_Element> Range { get { return _range; } }
/// <summary>
/// Inverts this constraint (this iff. !result)
/// !(Var in Range) iff. Var in (Var.Domain - Range)
/// </summary>
/// <returns></returns>
internal DomainConstraint<T_Variable, T_Element> InvertDomainConstraint()
{
return new DomainConstraint<T_Variable, T_Element>(_variable,
_variable.Domain.Difference(_range).AsReadOnly());
}
public override bool Equals(object obj)
{
if (Object.ReferenceEquals(this, obj)) { return true; }
DomainConstraint<T_Variable, T_Element> other = obj as DomainConstraint<T_Variable, T_Element>;
if (null == other) { return false; }
if (_hashCode != other._hashCode) { return false; }
return (_range.SetEquals(other._range) && _variable.Equals(other._variable));
}
public override int GetHashCode()
{
return _hashCode;
}
public override string ToString()
{
return StringUtil.FormatInvariant("{0} in [{1}]",
_variable, _range);
}
}
}
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