/// FACTORIAL_FACTOR: PRIMARY '!'? Factor
/// 5!
private ASTNode ParseFactorialFactor( )
{
var node = ParsePrimary();
if (IsNext(Token.TokenType.Factorial))
{
node = new FactorialUnaryOperatorASTNode(Accept( ), node);
}
return(node);
}
protected double Evaluate(FactorialUnaryOperatorASTNode node)
{
int fact(int x) => x == 1 ? 1 : x *fact(x - 1);
var value = ( int )Evaluate(node.Target as dynamic);
if (value < 0)
{
throw new Exception("Factorial only supports Positive Integers");
}
return(fact(value));
}
/// FACTORIAL_FACTOR: PRIMARY '!'?
private bool TryParseFactorialFactor(out ASTNode node)
{
if (TryParsePrimary(out node))
{
if (IsNext(Token.TokenType.Factorial))
{
node = new FactorialUnaryOperatorASTNode(Accept( ), node);
}
}
return(node != null);
}