/// <summary>
/// Creates a leaf with LeafCondition pred.
/// If simplify=true, checks if pred is unsat (returns False) or valid (returns True).
/// Assumes that if simplify=false then pred is neither unsat nor valid.
/// </summary>
public BDG <T, S> MkLeaf(T pred, bool simplify = false)
{
BDG <T, S> val;
if (simplify)
{
if (!MkLeafCache1.TryGetValue(pred, out val))
{
if (!leafAlgebra.IsSatisfiable(pred))
{
val = _False;
}
else if (!leafAlgebra.IsSatisfiable(leafAlgebra.MkNot(pred)))
{
val = _True;
}
else
{
val = new BDG <T, S>(this, default(S), pred, null, null);
}
MkLeafCache1[pred] = val;
}
}
else
{
if (!MkLeafCache2.TryGetValue(pred, out val))
{
val = new BDG <T, S>(this, default(S), pred, null, null);
MkLeafCache2[pred] = val;
}
}
return(val);
}
internal BDG(CartesianAlgebra <T, S> alg,
S nodePred, T leafPred, BDG <T, S> tCase, BDG <T, S> fCase)
{
this.algebra = alg;
this.BranchCondition = nodePred;
this.LeafCondition = leafPred;
this.TrueCase = tCase;
this.FalseCase = fCase;
this.Depth = (tCase == null ? 0 : Math.Max(tCase.Depth, fCase.Depth) + 1);
}
public CartesianAlgebra(IBooleanAlgebra <T> leafAlg, IBooleanAlgebra <S> nodeAlg)
{
this.leafAlgebra = leafAlg;
this.nodeAlgebra = nodeAlg;
this._True = new BDG <T, S>(this, default(S), leafAlg.True, null, null);
this._False = new BDG <T, S>(this, default(S), leafAlg.False, null, null);
MkLeafCache1[leafAlg.True] = _True;
MkLeafCache2[leafAlg.True] = _True;
MkLeafCache1[leafAlg.False] = _False;
MkLeafCache2[leafAlg.False] = _False;
MkNotCache[_True] = _False;
MkNotCache[_False] = _True;
this.mintermGenerator = new MintermGenerator <IMonadicPredicate <T, S> >(this);
}
public IMonadicPredicate <T, S> MkAnd(IMonadicPredicate <T, S> predicate1, IMonadicPredicate <T, S> predicate2)
{
//using Depth as a heuristic
BDG <T, S> p1 = (BDG <T, S>)predicate1;
BDG <T, S> p2 = (BDG <T, S>)predicate2;
if (p1.Depth <= p2.Depth)
{
return(p2.MkAnd(p1));
}
else
{
return(p1.MkAnd(p2));
}
}
/// <summary>
/// Assumes that pred is sat and ~pred is sat
/// </summary>
internal BDG <T, S> MkNode(S pred, BDG <T, S> t, BDG <T, S> f)
{
if (t == f)
{
return(t);
}
BDG <T, S> val;
var key = new Tuple <S, BDG <T, S>, BDG <T, S> >(pred, t, f);
if (!MkNodeCache.TryGetValue(key, out val))
{
val = new BDG <T, S>(this, pred, default(T), t, f);
MkNodeCache[key] = val;
}
return(val);
}
/// <summary>
/// Apply the transformation f to all leaves.
/// </summary>
internal BDG <T, S> TransformLeaves(Func <T, T> func)
{
BDG <T, S> val = null;
var key = new Tuple <Func <T, T>, BDG <T, S> >(func, this);
//if (!Algebra.TransformLeavesCache.TryGetValue(key, out val))
//{
if (this.IsLeaf)
{
var newPred = func(LeafCondition);
val = algebra.MkLeaf(newPred, true);
}
else
{
var t = this.TrueCase.TransformLeaves(func);
var f = this.FalseCase.TransformLeaves(func);
val = algebra.MkNode(this.BranchCondition, t, f);
}
//Algebra.TransformLeavesCache[key] = val;
//}
return(val);
}
/// <summary>
/// Maintains the node invariant: sat(path & nodePred) and sat(path & ~nodePred)
/// </summary>
BDG <T, S> MkAnd(S path, BDG <T, S> that)
{
var key = new Tuple <S, BDG <T, S>, BDG <T, S> >(path, this, that);
BDG <T, S> val;
if (!algebra.MkAndCache.TryGetValue(key, out val))
{
if (this.IsLeaf)
{
if (path.Equals(algebra.nodeAlgebra.True))
{
val = that.RestrictLeaves(this.LeafCondition);
}
else
{
val = that.Restrict(path, this.LeafCondition);
}
}
else if (that.IsLeaf)
{
val = this.RestrictLeaves(that.LeafCondition); //path is not relevant
}
else
{
var path_and_thatCond = algebra.nodeAlgebra.MkAnd(path, that.BranchCondition);
if (!algebra.nodeAlgebra.IsSatisfiable(path_and_thatCond))
{
//path implies ~that.BranchCondition
var t = this.TrueCase.MkAnd(algebra.nodeAlgebra.MkAnd(path, this.BranchCondition), that.FalseCase);
var f = this.FalseCase.MkAnd(algebra.nodeAlgebra.MkAnd(path, algebra.nodeAlgebra.MkNot(this.BranchCondition)), that.FalseCase);
if (t == this.TrueCase && f == this.FalseCase)
{
val = this;
}
else
{
val = this.algebra.MkNode(this.BranchCondition, t, f);
}
}
else
{
var path_and_not_thatCond = algebra.nodeAlgebra.MkAnd(path, algebra.nodeAlgebra.MkNot(that.BranchCondition));
if (!algebra.nodeAlgebra.IsSatisfiable(path_and_not_thatCond))
{
//path implies that.BranchCondition
var t = this.TrueCase.MkAnd(algebra.nodeAlgebra.MkAnd(path, this.BranchCondition), that.TrueCase);
var f = this.FalseCase.MkAnd(algebra.nodeAlgebra.MkAnd(path, algebra.nodeAlgebra.MkNot(this.BranchCondition)), that.TrueCase);
if (t == this.TrueCase && f == this.FalseCase)
{
val = this;
}
else
{
val = this.algebra.MkNode(this.BranchCondition, t, f);
}
}
else
{ //both cases are possible
var t = this.TrueCase.MkAnd(algebra.nodeAlgebra.MkAnd(path, this.BranchCondition), that);
var f = this.FalseCase.MkAnd(algebra.nodeAlgebra.MkAnd(path, algebra.nodeAlgebra.MkNot(this.BranchCondition)), that);
if (t == this.TrueCase && f == this.FalseCase)
{
val = this;
}
else
{
val = this.algebra.MkNode(this.BranchCondition, t, f);
}
}
}
}
algebra.MkAndCache[key] = val;
}
return(val);
}
/// <summary>
/// Makes the conjunction of this and that
/// </summary>
public BDG <T, S> MkAnd(BDG <T, S> that)
{
return(MkAnd(algebra.nodeAlgebra.True, that));
}