/// <summary>
/// Instantiate a new operator node and make sure that its value is as specified
/// and the tree rooted at this node has the specified number of operand nodes.
/// </summary>
/// <param name="goal"></param>
/// <param name="numberOfNewNodes"></param>
public OperatorNode(int goal, int numberOfNewNodes = 2)
{
int left, right;
char op;
// Choose a random valid operator for this node and split the goal
do
{
op = Tree.operators.GetRandomElement();
} while (!SplitHelper.SplitValue(goal, op, out left, out right));
Operator = new Operator(op);
Left = new OperandNode(left);
Right = new OperandNode(right);
int toLeft, toRight;
// Distribute the number of new operands to be made between the two sides
SplitHelper.SplitNumberOfOperands(left, right, numberOfNewNodes, out toLeft, out toRight);
Left = Left.Expand(toLeft);
Right = Right.Expand(toRight);
}