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//---------------------------------------------------------------------
// <copyright file="Literal.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Text;
using System.Globalization;
using System.Collections.ObjectModel;
using System.Diagnostics;
namespace System.Data.Common.Utils.Boolean
{
/// <summary>
/// Represents a literal in a normal form expression of the form:
///
/// Term
///
/// or
///
/// !Term
/// </summary>
/// <typeparam name="T_Identifier"></typeparam>
internal sealed class Literal<T_Identifier> : NormalFormNode<T_Identifier>,
IEquatable<Literal<T_Identifier>>
{
private readonly TermExpr<T_Identifier> _term;
private readonly bool _isTermPositive;
/// <summary>
/// Initialize a new literal.
/// </summary>
/// <param name="term">Term</param>
/// <param name="isTermPositive">Sign of term</param>
internal Literal(TermExpr<T_Identifier> term, bool isTermPositive)
: base(isTermPositive ? (BoolExpr<T_Identifier>)term : (BoolExpr<T_Identifier>)new NotExpr<T_Identifier>(term))
{
Debug.Assert(null != term);
_term = term;
_isTermPositive = isTermPositive;
}
/// <summary>
/// Gets literal term.
/// </summary>
internal TermExpr<T_Identifier> Term
{
get { return _term; }
}
/// <summary>
/// Gets sign of term.
/// </summary>
internal bool IsTermPositive
{
get { return _isTermPositive; }
}
/// <summary>
/// Creates a negated version of this literal.
/// </summary>
/// <returns>!this</returns>
internal Literal<T_Identifier> MakeNegated()
{
return IdentifierService<T_Identifier>.Instance.NegateLiteral(this);
}
public override string ToString()
{
return StringUtil.FormatInvariant("{0}{1}",
_isTermPositive ? String.Empty : "!",
_term);
}
public override bool Equals(object obj)
{
Debug.Fail("use typed Equals");
return Equals(obj as Literal<T_Identifier>);
}
public bool Equals(Literal<T_Identifier> other)
{
return null != other &&
other._isTermPositive == _isTermPositive &&
other._term.Equals(_term);
}
public override int GetHashCode()
{
return _term.GetHashCode();
}
}
}
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