//------------------------------------------------------------------------------------------------------------
private static decimal calculate(decimal y, char op, decimal x)
{
string name = "PostfixEvaluator calculate";
if (!Toolbelt.IsOperator(op))
{
throw new ArgumentException($"{name} op value is not a valid operator ({op})");
}
switch (op)
{
case '^':
return((int)y ^ (int)x);
case '+':
return(y + x);
case '-':
return(y - x);
case '*':
return(y * x);
case '/':
return(y / x);
}
return(0m);
}
//------------------------------------------------------------------------------------------------------------
public static decimal Evaluate(string postfix)
{
bool debug = false;
if (Toolbelt.HasLetters(postfix))
{
return(0M);
}
Stack <string> expression = new Stack <string>(postfix.Split(' ').Reverse());
Stack <decimal> operands = new Stack <decimal>();
while (expression.Count > 0)
{
if (debug)
{
Toolbelt.DisplayStack(expression, "expression");
Toolbelt.DisplayStack(operands, "operands");
}
string working = expression.Pop();
decimal value;
if (Decimal.TryParse(working, out value))
{
operands.Push(value);
}
else if (working.Length == 1 && Toolbelt.IsOperator(working[0]))
{
if (operands.Count >= 2)
{
var x = operands.Pop();
var y = operands.Pop();
operands.Push(calculate(y, working[0], x));
}
}
}
return(operands.Pop());
}
