/// <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));
}
/// <summary>
/// Initialize an encapsulated variable domain value with an encapsulated variable and value sets.
/// </summary>
internal EncapsulatedVariableDomainValue(EncapsulatedVariable encapsulatedVariable, IEnumerable <ValueSet> valueSets)
{
_encapsulatedVariable = encapsulatedVariable;
_sets = new List <ValueSet>(valueSets);
}