static void DoCalculation(SmashTheState state, OperatorType op)
{
double result;
if (op != OperatorType.UnaryMinus)
{
double right = state.PopOutput();
double left = state.PopOutput();
switch (op)
{
case OperatorType.Add:
result = left + right;
break;
case OperatorType.Sub:
result = left - right;
break;
case OperatorType.Mult:
result = left * right;
break;
case OperatorType.Div:
result = left / right;
break;
case OperatorType.Pow:
result = Math.Pow(left, right);
break;
default:
throw new ArgumentException("Operator not supported: " + op, nameof(op));
}
}
// OperatorType.UnaryMinus
else
{
result = state.PopOutput() * -1;
}
state.Push(result);
}
static void DoFunction(SmashTheState state)
{
var token = (CalcFuncToken)state.PopOpStack();
var func = token.Func;
double[] args = new double[func.ArgCount];
// Reverse, since the first out was the last argument in.
for (int i = func.ArgCount - 1; i >= 0; i--)
{
args[i] = state.PopOutput();
}
state.Push(func.Apply(args));
}
public static double Calculate(VerifiedExpression expr)
{
if (expr == null)
{
throw new ArgumentNullException(nameof(expr));
}
if (!expr.Success)
{
throw new ArgumentException("Expression must be successfully parsed.");
}
var state = new SmashTheState(); // But not really :(
foreach (var token in expr.Expression)
{
switch (token.Type)
{
// --- Simple pushing cases ---
case TokenType.Number:
case TokenType.Symbol:
state.Push(((INumberValue)token).NumberValue);
break;
case TokenType.Function:
case TokenType.ParenOpen:
state.Push(token);
break;
// --- Do the ShuntingYard ---
// Apply the operators as described by the algorithm, see `ToPopStack` for more details.
case TokenType.Operator:
while (state.ToPopStack((CalcOpToken)token))
{
DoCalculation(state);
}
state.Push(token);
break;
// Behaves like a closing parenthesis, but don't discard the opening parenthesis.
case TokenType.ArgSeperator:
ConsumeTillOpenParen(state, false);
break;
// Apply all the remaining operators until we encounter the opening parenthesis,
// discard it afterwards.
case TokenType.ParenClose:
ConsumeTillOpenParen(state, true);
// If after that the top of the stack is a function, apply it.
if (state.NextIsFunction)
{
DoFunction(state);
}
break;
}
}
// If there are still operators on the opStack, consume them until stack is exhausted.
while (state.OpCount > 0)
{
DoCalculation(state);
}
// There should be only 1 value left, the final result. Pop and return that.
return(state.PopOutput());
}