private static string Evaluate(string input)
{
var command = Command.Parse(input);
switch (command.Operation)
{
case Operation.Unknown:
return("Invalid input!");
case Operation.Push:
if (!calculator.TryPush(command.Argument))
{
return("Stack is full or number is invalid!");
}
return(string.Empty);
case Operation.Pop:
calculator.Pop();
return(string.Empty);
case Operation.Add:
if (calculator.TryAdd())
{
return(calculator.Stack.Last().ToString());
}
else
{
return("Not enough numbers on the stack!");
}
case Operation.Sub:
if (calculator.TrySub())
{
return(calculator.Stack.Last().ToString());
}
else
{
return("Not enough numbers on the stack!");
}
default:
return(string.Empty);
}
}