/// <summary>
/// Build one or more arcs from the ternary constraint expression.
/// </summary>
/// <remarks>
/// There will be more than one arc because binarization of the expression requires introducing an
/// encapsulated variable between the two variables involved in the expression.
/// </remarks>
/// <param name="expressionConstraintNode">Expression constraint abstract syntax tree.</param>
/// <returns>One or more arcs.</returns>
private IReadOnlyCollection <Arc> BuildTernaryExpression(ConstraintExpressionNode expressionConstraintNode)
{
var arcAccumulator = new List <Arc>();
if (!expressionConstraintNode.InnerExpression.RightExpression.IsLiteral)
{
var left = CreateNodeFrom(expressionConstraintNode.InnerExpression.LeftExpression);
var right = CreateNodeFrom(expressionConstraintNode.InnerExpression.RightExpression);
var encapsulatedVariable = new EncapsulatedVariable("U");
var encapsulatedVariableNode = new EncapsulatedVariableNode(encapsulatedVariable);
var arc1 = new Arc(left, encapsulatedVariableNode, new EncapsulatedVariableConnector(left, encapsulatedVariableNode, new EncapsulatedSelector(1)));
arcAccumulator.Add(arc1);
var arc2 = new Arc(right, encapsulatedVariableNode, new EncapsulatedVariableConnector(encapsulatedVariableNode, right, new EncapsulatedSelector(2)));
arcAccumulator.Add(arc2);
var ternaryConstraintExpression = new TernaryConstraintExpression(expressionConstraintNode, encapsulatedVariableNode, arc1, arc2);
var encapsulatedVariableDomainValue = ComputeEncapsulatedDomain(ternaryConstraintExpression);
encapsulatedVariable.DomainValue = encapsulatedVariableDomainValue;
var expressionSolution = new TernaryConstraintExpressionSolution(ternaryConstraintExpression, encapsulatedVariableDomainValue);
_modelSolverMap.AddTernaryExpressionSolution(expressionSolution);
}
else
{
var left = CreateNodeFrom(expressionConstraintNode.InnerExpression.LeftExpression);
var encapsulatedVariable = new EncapsulatedVariable("U");
var encapsulatedVariableNode = new EncapsulatedVariableNode(encapsulatedVariable);
var arc1 = new Arc(left, encapsulatedVariableNode, new EncapsulatedVariableConnector(left, encapsulatedVariableNode, new EncapsulatedSelector(1)));
arcAccumulator.Add(arc1);
var ternaryConstraintExpression = new TernaryConstraintExpression(expressionConstraintNode, encapsulatedVariableNode, arc1, arc1);
var encapsulatedVariableDomainValue = ComputeEncapsulatedDomain(ternaryConstraintExpression);
encapsulatedVariable.DomainValue = encapsulatedVariableDomainValue;
var expressionSolution = new TernaryConstraintExpressionSolution(ternaryConstraintExpression, encapsulatedVariableDomainValue);
_modelSolverMap.AddTernaryExpressionSolution(expressionSolution);
}
return(new ReadOnlyCollection <Arc>(arcAccumulator));
}
private EncapsulatedVariableDomainValue ComputeEncapsulatedDomain(TernaryConstraintExpression ternaryConstraintExpression)
{
var encapsulatedVariableCalculator = new EncapsulatedVariablePermutationCalculator(_modelSolverMap, _valueMapper);
return(encapsulatedVariableCalculator.Compute(ternaryConstraintExpression));
}
internal EncapsulatedVariableDomainValue Compute(TernaryConstraintExpression ternaryConstraint)
{
var valueSetAccumulator = new List <ValueSet>();
var leftSource = ternaryConstraint.GetLeftSource();
var leftPossibleValues = leftSource.PossibleValues;
var expression = ternaryConstraint.ExpressionNode;
IReadOnlyCollection <int> rightPossibleValues;
if (!expression.InnerExpression.RightExpression.IsLiteral)
{
var rightSource = ternaryConstraint.GetRightSource();
rightPossibleValues = new ReadOnlyCollection <int>(rightSource.PossibleValues.ToList());
}
else
{
var lhsVariable = _modelSolverMap.GetModelVariableByName(leftSource.VariableName);
var range = _valueMapper.GetDomainValueFor(lhsVariable);
var modelValue = expression.InnerExpression.RightExpression.GetLiteral();
var solverValue = range.MapTo(modelValue);
rightPossibleValues = new ReadOnlyCollection <int>(new List <int> {
solverValue
});
}
foreach (var leftPossibleValue in leftPossibleValues)
{
foreach (var rightPossibleValue in rightPossibleValues)
{
switch (ternaryConstraint.ExpressionNode.InnerExpression.Operator)
{
case OperatorType.Equals:
if (leftPossibleValue == rightPossibleValue)
{
if (!expression.InnerExpression.RightExpression.IsLiteral)
{
var rightSource = ternaryConstraint.GetRightSource();
var valueSet = new ValueSet(new[] { new Value(_modelSolverMap.GetSolverVariableByName(leftSource.VariableName), leftPossibleValue),
new Value(_modelSolverMap.GetSolverVariableByName(rightSource.VariableName), rightPossibleValue) });
valueSetAccumulator.Add(valueSet);
}
else
{
var valueSet = new ValueSet(new[] { new Value(_modelSolverMap.GetSolverVariableByName(leftSource.VariableName), leftPossibleValue) });
valueSetAccumulator.Add(valueSet);
}
}
break;
case OperatorType.NotEqual:
if (leftPossibleValue != rightPossibleValue)
{
if (!expression.InnerExpression.RightExpression.IsLiteral)
{
var rightSource = ternaryConstraint.GetRightSource();
var valueSet = new ValueSet(new[] { new Value(_modelSolverMap.GetSolverVariableByName(leftSource.VariableName), leftPossibleValue),
new Value(_modelSolverMap.GetSolverVariableByName(rightSource.VariableName), rightPossibleValue) });
valueSetAccumulator.Add(valueSet);
}
else
{
var valueSet = new ValueSet(new[] { new Value(_modelSolverMap.GetSolverVariableByName(leftSource.VariableName), leftPossibleValue) });
valueSetAccumulator.Add(valueSet);
}
}
break;
default:
throw new NotImplementedException();
}
}
}
return(new EncapsulatedVariableDomainValue(ternaryConstraint.EncapsulatedVariable, valueSetAccumulator));
}
