/// <summary>
/// Evaluates the given list of tokens and returns the result.
/// Tokens must appear in postfix order.
/// </summary>
/// <param name="tokens">List of tokens to evaluate.</param>
/// <returns></returns>
protected double ExecuteTokens(List <string> tokens)
{
Stack <double> stack = new Stack <double>();
double tmp, tmp2;
foreach (string token in tokens)
{
// Is this a value token?
double tokenValue = 0;
if (double.TryParse(token, out tokenValue))
{
stack.Push(tokenValue);
}
else if (token == "+")
{
stack.Push(stack.Pop() + stack.Pop());
}
else if (token == "-")
{
tmp = stack.Pop();
tmp2 = stack.Pop();
stack.Push(tmp2 - tmp);
}
else if (token == "×" || token == "*")
{
stack.Push(stack.Pop() * stack.Pop());
}
else if (token == "÷" || token == "/")
{
tmp = stack.Pop();
tmp2 = stack.Pop();
stack.Push(tmp2 / tmp);
}
else if (token == "^")
{
tmp = stack.Pop();
tmp2 = stack.Pop();
stack.Push(Math.Pow(tmp2, tmp));
}
else if (token == UnaryMinus)
{
double value = stack.Pop();
if (value > 0)
{
stack.Push(-value);
}
}
// Logical
// AND
else if (token == "&")
{
stack.Push(((long)stack.Pop()) & ((long)stack.Pop()));
}
// OR
else if (token == "|")
{
stack.Push(((long)stack.Pop()) | ((long)stack.Pop()));
}
// XOR
else if (token == "⊕")
{
stack.Push(((long)stack.Pop()) ^ ((long)stack.Pop()));
}
// RIGHT SHIFT
else if (token == "<")
{
tmp = stack.Pop();
tmp2 = stack.Pop();
stack.Push(((long)tmp2) << ((int)tmp));
}
// LEFT SHIFT
else if (token == ">")
{
tmp = stack.Pop();
tmp2 = stack.Pop();
stack.Push(((long)tmp2) >> ((int)tmp));
}
// LEFT SHIFT
else if (token == "%")
{
tmp = stack.Pop();
tmp2 = stack.Pop();
stack.Push((long)tmp2 % (int)tmp);
}
//Statistical
else if (token == "P")
{
tmp = stack.Pop();
tmp2 = stack.Pop();
// n! / (n-k)!
double val = double.Parse(Calc_MainPage.factorial(tmp2)) / double.Parse(Calc_MainPage.factorial(tmp2 - tmp));
stack.Push(val);
}
else if (token == "C")
{
tmp = stack.Pop();
tmp2 = stack.Pop();
// n! / (k! * (n-k)!)
double val = double.Parse(Calc_MainPage.factorial(tmp2)) / (double.Parse(Calc_MainPage.factorial(tmp2 - tmp)) * double.Parse(Calc_MainPage.factorial(tmp)));
stack.Push(val);
}
}
// Remaining item on stack contains result
return((stack.Count > 0) ? stack.Pop() : 0.0);
}