/// <summary>
/// Constructs a new Expression Tree for a postfix Expression
/// </summary>
/// <param name="postfixParse">Postfix expression string</param>
/// <returns>Root of the constructed tree</returns>
private ExpressionTreeNode ConstructPostfixTree(List <string> postfixParse)
{
Stack <ExpressionTreeNode> treeStack = new Stack <ExpressionTreeNode>();
for (int i = 0; i < postfixParse.Count; i++)
{
// If operator, pop twice and from stack and create new tree
if (operatorFactory.IsValidOperator(postfixParse[i].ElementAt(0)))
{
ExpressionTreeNode newRight = treeStack.Pop();
ExpressionTreeNode newLeft = treeStack.Pop();
OperatorExpressionTreeNode newRoot = operatorFactory.CreateOperatorNode(postfixParse[i].ElementAt(0));
newRoot.Right = newRight;
newRoot.Left = newLeft;
treeStack.Push(newRoot);
}
else
{
// Create a new variable or constant node and push to the stack
treeStack.Push(this.BuildSimpleNode(postfixParse[i]));
}
}
if (treeStack.Count == 1)
{
return(treeStack.Pop());
}
else
{
// Throw exception?
return(null);
}
}
/// <summary>
/// Initializes a new instance of the <see cref="ExpressionTree"/> class.
/// Parses and Expression string and builds the resulting tree
/// </summary>
/// <param name="expression">string expression</param>
public ExpressionTree(string expression)
{
this.variables = new Dictionary <string, double>();
this.expressionParse = this.ConvertToPostfix(expression);
this.root = this.ConstructPostfixTree(expressionParse);
}
