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//
// NullExpr.cs
//
// Authors:
// Alexander Chebaturkin (chebaturkin@gmail.com)
//
// Copyright (C) 2011 Alexander Chebaturkin
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Collections.Generic;
using Mono.CodeContracts.Static.ControlFlow;
using Mono.CodeContracts.Static.DataStructures;
namespace Mono.CodeContracts.Static.Analysis.ExpressionAnalysis.Expressions {
sealed class NullExpr<TSymbolicValue> : Expr<TSymbolicValue> where TSymbolicValue : IEquatable<TSymbolicValue> {
public static readonly Expr<TSymbolicValue> Instance = new NullExpr<TSymbolicValue> ();
private NullExpr ()
{
}
#region Overrides of Expression
public override IEnumerable<TSymbolicValue> Variables
{
get { yield break; }
}
public override Result Decode<Data, Result, Visitor> (APC pc, TSymbolicValue dest, Visitor visitor, Data data)
{
return visitor.LoadNull (pc, dest, data);
}
public override Expr<TSymbolicValue> Substitute (IImmutableMap<TSymbolicValue, Sequence<TSymbolicValue>> substitutions)
{
return this;
}
public override bool IsContained (IImmutableSet<TSymbolicValue> candidates)
{
return false;
}
public override bool Contains (TSymbolicValue symbol)
{
return false;
}
public override string ToString ()
{
return "Null()";
}
public override bool Equals (Expr<TSymbolicValue> other)
{
return other == this;
}
#endregion
}
}
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