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//
// FlatDomain.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.IO;
namespace Mono.CodeContracts.Static.Lattices {
/// <summary>
/// Represents domain, where abstract values are disjunct, and their join/meet turns into Top/Bottom respectively
/// </summary>
/// <example>
/// Top
/// / | \
/// v1 v2 v3
/// \ | /
/// Bot
/// </example>
/// <typeparam name="T"></typeparam>
public struct FlatDomain<T> : IAbstractDomain<FlatDomain<T>>, IEquatable<FlatDomain<T>>
where T : IEquatable<T> {
public static readonly FlatDomain<T> BottomValue = new FlatDomain<T> (DomainKind.Bottom);
public static readonly FlatDomain<T> TopValue = new FlatDomain<T> (DomainKind.Top);
public readonly T Value;
readonly DomainKind state;
FlatDomain (DomainKind state)
{
this.state = state;
Value = default(T);
}
public FlatDomain (T value)
{
state = DomainKind.Normal;
Value = value;
}
public static implicit operator FlatDomain<T> (T value)
{
return new FlatDomain<T> (value);
}
#region Implementation of IAbstractDomain<FlatDomain<T>>
public FlatDomain<T> Top { get { return TopValue; } }
public FlatDomain<T> Bottom { get { return BottomValue; } }
public bool IsTop { get { return state == DomainKind.Top; } }
public bool IsBottom { get { return state == DomainKind.Bottom; } }
public FlatDomain<T> Join (FlatDomain<T> that, bool widening, out bool weaker)
{
if (IsTop || that.IsBottom) {
weaker = false;
return this;
}
if (that.IsTop) {
weaker = !IsTop;
return that;
}
if (IsBottom) {
weaker = !that.IsBottom;
return that;
}
if (Value.Equals (that.Value)) {
weaker = false;
return that;
}
weaker = true;
return TopValue;
}
public FlatDomain<T> Widen (FlatDomain<T> that)
{
// no widening - it's finite lattice
return Join (that);
}
public FlatDomain<T> Join (FlatDomain<T> that)
{
FlatDomain<T> result;
if (this.TryTrivialJoin (that, out result))
return result;
// this and that must be normal here
return Value.Equals (that.Value) ? this : TopValue;
}
public FlatDomain<T> Meet (FlatDomain<T> that)
{
FlatDomain<T> result;
if (this.TryTrivialMeet (that, out result))
return result;
return Value.Equals (that.Value) ? this : BottomValue;
}
public bool LessEqual (FlatDomain<T> that)
{
bool result;
if (this.TryTrivialLessEqual (that, out result))
return result;
return Value.Equals (that.Value);
}
public FlatDomain<T> ImmutableVersion ()
{
return this;
}
public FlatDomain<T> Clone ()
{
return this;
}
public void Dump (TextWriter tw)
{
if (IsTop)
tw.WriteLine ("Top");
else if (IsBottom)
tw.WriteLine (this.BottomSymbolIfAny ());
else
tw.WriteLine ("<{0}>", Value);
}
public override string ToString ()
{
if (IsTop)
return "Top";
if (IsBottom)
return this.BottomSymbolIfAny ();
return string.Format ("<{0}>", Value);
}
#endregion
public bool Equals (FlatDomain<T> that)
{
if (!this.IsNormal ())
return state == that.state;
return that.IsNormal () && Value.Equals (that.Value);
}
}
enum DomainKind {
Normal = 0,
Top,
Bottom
}
}
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