/// <summary>
/// Evaluates the expression
/// </summary>
/// <returns>The result of evaluation</returns>
public double Evaluate()
{
//Create a clone of expression because we don't want to mess with it
CloneableStack <Symbol> expr = expression.Clone();
Stack <Symbol> tempStack = new Stack <Symbol>();
double[] values;
while (expr.Count() > 0)
{
if (!expr.Peek().isOperator)
{
tempStack.Push(expr.Pop());
}
else
{
//Pop values, tempStack should only be 0 op symbols
values = new double[expr.Peek().nOps];
for (int i = 0; i < values.Length; i++)
{
values[i] = tempStack.Pop().eval(null);
}
tempStack.Push(new Symbol(expr.Pop().eval(values)));
}
}
return(tempStack.Pop().eval(null));
}
/// <summary>
/// Converts an infix expression represented an array of strings to a
/// corresponding RPN expression as a stack.
/// </summary>
/// <param name="inputTokens"></param>
/// <returns></returns>
private CloneableStack <Symbol> InfixToRPN(string[] inputTokens)
{
//ArrayList outList = new ArrayList();
CloneableStack <Symbol> result = new CloneableStack <Symbol>(0);
Stack <string> stack = new Stack <string>();
//for all the input tokens read the next token
foreach (string token in inputTokens)
{
if (IsOperator(token))
{
//If token is an operator
while (stack.Count != 0 && IsOperator(stack.Peek()))
{
if ((IsAssociative(token, LEFT_ASSOC) && CmpPrecedence(token, stack.Peek()) <= 0) ||
(IsAssociative(token, RIGHT_ASSOC) && CmpPrecedence(token, stack.Peek()) < 0))
{
result.Push(ToSymbol(stack.Pop()));
continue;
}
break;
}
//Push the new operator on the stack
stack.Push(token);
}
else if (token.Equals("("))
{
stack.Push(token);
}
else if (token.Equals(")"))
{
while (stack.Count != 0 && !stack.Peek().Equals("("))
{
result.Push(ToSymbol(stack.Pop()));
}
stack.Pop();
}
else
{
result.Push(ToSymbol(token));
}
}
while (stack.Count != 0)
{
result.Push(ToSymbol(stack.Pop()));
}
CloneableStack <Symbol> actualResult = new CloneableStack <Symbol>(result.Count());
while (result.Count() > 0)
{
actualResult.Push(result.Pop());
}
return(actualResult);
}
public void Pop()
{
curIndent -= GetIndent(indentStack.Pop());
Update();
}