private Node determineNode(string expression, int operandBegin, int i)
{
string operandName = expression.Substring(operandBegin, i - operandBegin);
// Figure out if operand is constant or variable valued
if (65 < expression[operandBegin])
{
// We know that the operand, left of current operator, is a variable
if (variableDictionary.ContainsKey(operandName) == true)
{
VarNode newNode = new VarNode(operandName, variableDictionary[operandName]);
return(newNode);
}
else
{
VarNode newNode = new VarNode(operandName, 0);
variableDictionary.Add(operandName, newNode.NodeValue);
return(newNode);
}
}
else
{
// We know that the operand, left of current operator, is a constant
ConstNode newNode = new ConstNode(operandName, Convert.ToDouble(operandName));
return(newNode);
}
}
private double Eval(Node node)
{
//Evaluate based on the kind of node
ConstNode constnode = node as ConstNode;
if (constnode != null)
{
return(constnode.OpValue);
}
VarNode varnode = node as VarNode;
if (varnode != null)
{
try
{ return(variableDict[varnode.Name]); }
catch
{
Console.WriteLine("Variable " + varnode.Name + " has not been defined. Continuing evaluation with variable equal to 0.");
}
}
OpNode opnode = node as OpNode;
if (opnode != null)
{
switch (opnode.Op)
{
case '+':
return(Eval(opnode.Left) + Eval(opnode.Right));
case '-':
return(Eval(opnode.Left) - Eval(opnode.Right));
case '*':
return(Eval(opnode.Left) * Eval(opnode.Right));
case '/':
return(Eval(opnode.Left) / Eval(opnode.Right));
}
}
return(0);
}
private double Eval(Node node)
{
//Evaluate based on the kind of node
ConstNode constnode = node as ConstNode;
if (constnode != null)
{
return(constnode.OpValue);
}
VarNode varnode = node as VarNode;
if (varnode != null)
{
// used to be a try/catch, but now we set every new variable to 0 when the tree is made, so there will always be a value to obtain.
return(variableDict[varnode.Name]);
}
OpNode opnode = node as OpNode;
if (opnode != null)
{
switch (opnode.Op)
{
case '+':
return(Eval(opnode.Left) + Eval(opnode.Right));
case '-':
return(Eval(opnode.Left) - Eval(opnode.Right));
case '*':
return(Eval(opnode.Left) * Eval(opnode.Right));
case '/':
return(Eval(opnode.Left) / Eval(opnode.Right));
}
}
return(0);
}
