/// <summary>
/// This is the modified Shunting Yard algorithm. First it reads the symbols/tokens
/// and pushes them to the correct stack. It will then call calulate on certain operators,
/// this follows order of presidence/BIDMAS
/// </summary>
/// <returns></returns>
public double ShuntYard()
{
int count = 0;
while (count < LT.symbols.Length)
{
switch (LT.GetSymbol(count).Type)
{
case Tokens.Integer:
Numbers.Push(LT.GetSymbol(count++).Value);
break;
case Tokens.Double:
Numbers.Push(LT.GetSymbol(count++).Value);
break;
case Tokens.Variable:
Numbers.Push(LT.GetSymbol(count++).Value);
break;
case Tokens.Equal:
Operators.Push(LT.GetSymbol(count++).Type);
break;
case Tokens.Plus:
while (Operators.Count > 0 && (Tokens)Operators.Peek() != Tokens.Left_Parenthesis && (Tokens)Operators.Peek() != Tokens.Equal)
{
Calculate();
}
Operators.Push(LT.GetSymbol(count++).Type);
break;
case LookupTable.Tokens.Minus:
while (Operators.Count > 0 && (Tokens)Operators.Peek() != Tokens.Left_Parenthesis && (Tokens)Operators.Peek() != Tokens.Equal)
{
Calculate();
}
Operators.Push(LT.GetSymbol(count++).Type);
break;
case LookupTable.Tokens.Multiply:
while (Operators.Count > 0 && (Tokens)Operators.Peek() != Tokens.Left_Parenthesis &&
(Tokens)Operators.Peek() != Tokens.Plus && (Tokens)Operators.Peek() != Tokens.Minus &&
(Tokens)Operators.Peek() != Tokens.Equal)
{
Calculate();
}
Operators.Push(LT.GetSymbol(count++).Type);
break;
case LookupTable.Tokens.Divide:
while (Operators.Count > 0 && (Tokens)Operators.Peek() != Tokens.Left_Parenthesis &&
(Tokens)Operators.Peek() != Tokens.Plus && (Tokens)Operators.Peek() != Tokens.Minus &&
(Tokens)Operators.Peek() != Tokens.Equal)
{
Calculate();
}
Operators.Push(LT.GetSymbol(count++).Type);
break;
case LookupTable.Tokens.Exponent:
while (Operators.Count > 0 && (Tokens)Operators.Peek() != Tokens.Left_Parenthesis &&
(Tokens)Operators.Peek() != Tokens.Plus && (Tokens)Operators.Peek() != Tokens.Minus &&
(Tokens)Operators.Peek() != Tokens.Equal && (Tokens)Operators.Peek() != Tokens.Multiply &&
(Tokens)Operators.Peek() != Tokens.Divide)
{
Calculate();
}
Operators.Push(LT.GetSymbol(count++).Type);
break;
case LookupTable.Tokens.Left_Parenthesis:
Operators.Push(LT.GetSymbol(count++).Type);
break;
case LookupTable.Tokens.Right_Parenthesis:
while (Operators.Count > 0 && (LookupTable.Tokens)Operators.Peek() != LookupTable.Tokens.Left_Parenthesis)
{
Calculate();
}
if ((LookupTable.Tokens)Operators.Peek() == LookupTable.Tokens.Left_Parenthesis)
{
Operators.Pop();
}
count++;
break;
default:
count++;
break;
}
}
//This is a fail safe to make sure that all operators are used.
while (Operators.Count > 0)
{
Calculate();
}
//This if exists as an assignment of a variable will not return back
//to the numbers stack.
if (Numbers.Count == 1)
{
return(Convert.ToDouble(Numbers.Pop()));
}
else
{
return(0);
}
}