/// <summary>
/// Appends the specified operator to the expression by first
/// reducing the operator stack and then pushing the new
/// operator on the stack.
/// </summary>
/// <param name="op">The operator to push.</param>
public void Append(ConstraintOperator op)
{
op.LeftContext = lastPushed;
if (lastPushed is ConstraintOperator)
{
SetTopOperatorRightContext(op);
}
// Reduce any lower precedence operators
ReduceOperatorStack(op.LeftPrecedence);
ops.Push(op);
lastPushed = op;
}
/// <summary>
/// Resolves this instance, returning a Constraint. If the builder
/// is not currently in a resolvable state, an exception is thrown.
/// </summary>
/// <returns>The resolved constraint</returns>
public IConstraint Resolve()
{
if (!IsResolvable)
{
throw new InvalidOperationException("A partial expression may not be resolved");
}
while (!ops.Empty)
{
ConstraintOperator op = ops.Pop();
op.Reduce(constraints);
}
return(constraints.Pop());
}
/// <summary>
/// Sets the top operator right context.
/// </summary>
/// <param name="rightContext">The right context.</param>
private void SetTopOperatorRightContext(object rightContext)
{
// Some operators change their precedence based on
// the right context - save current precedence.
int oldPrecedence = ops.Top.LeftPrecedence;
ops.Top.RightContext = rightContext;
// If the precedence increased, we may be able to
// reduce the region of the stack below the operator
if (ops.Top.LeftPrecedence > oldPrecedence)
{
ConstraintOperator changedOp = ops.Pop();
ReduceOperatorStack(changedOp.LeftPrecedence);
ops.Push(changedOp);
}
}
/// <summary>
/// Appends an operator to the expression and returns the
/// resulting expression itself.
/// </summary>
public ConstraintExpression Append(ConstraintOperator op)
{
Builder.Append(op);
return(this);
}
/// <summary> /// Pushes the specified operator onto the stack. /// </summary> /// <param name="op">The op.</param> public void Push(ConstraintOperator op) => _stack.Push(op);