private double Evaluate(Node node)
{
if (node != null)
{
if (node is OperatorNode)
{
OperatorNode opNode = node as OperatorNode;
double evaluation = opNode.Evaluate();
return(evaluation);
}
if (node is ConstantNode)
{
ConstantNode constNode = node as ConstantNode;
return(constNode.Value);
}
if (node is VariableNode)
{
VariableNode varNode = node as VariableNode;
return(this.Variables[varNode.Name]);
}
}
return(0);
}
/// <summary>
/// Evaluates the arithmetic logic of an expression tree.
/// </summary>
/// <param name="current">The head of the tree to be evaluated.</param>
/// <returns>Returns the evaluation of the expression tree.</returns>
private double EvaluateHelper(OperatorNode current)
{
// Both children are leaves.
if (!this.IsOperatorNode(current.Left) && !this.IsOperatorNode(current.Right))
{
double leftVal, rightVal;
if (this.IsVariableNode(current.Left))
{
leftVal = this.variables[current.Left.Value]; // Get left value from dictionary.
}
else
{
leftVal = Convert.ToDouble(current.Left.Value); // Get left value from left node.
}
if (this.IsVariableNode(current.Right))
{
rightVal = this.variables[current.Right.Value]; // Get right value from dictionary.
}
else
{
rightVal = Convert.ToDouble(current.Right.Value); // Get right value from right node.
}
return(current.Evaluate(leftVal, rightVal));
}
else if (!this.IsOperatorNode(current.Left))
{
// Only the right node is an operator node.
double leftVal;
if (this.IsVariableNode(current.Left))
{
leftVal = this.variables[current.Left.Value]; // Get left value from dictionary.
}
else
{
leftVal = Convert.ToDouble(current.Left.Value); // Get left value from left node.
}
return(current.Evaluate(leftVal, this.EvaluateHelper((OperatorNode)current.Right)));
}
else if (!this.IsOperatorNode(current.Right))
{
// Only the left node is an operator node.
double rightVal;
if (this.IsVariableNode(current.Right))
{
rightVal = this.variables[current.Right.Value]; // Get right value from dictionary.
}
else
{
rightVal = Convert.ToDouble(current.Right.Value); // Get right value from right node.
}
return(current.Evaluate(this.EvaluateHelper((OperatorNode)current.Left), rightVal));
}
else
{
// Both children are operator nodes.
OperatorNode leftNode = (OperatorNode)current.Left, rightNode = (OperatorNode)current.Right;
return(current.Evaluate(this.EvaluateHelper(leftNode), this.EvaluateHelper(rightNode)));
}
}