private 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("Only positive integers allowed.");
}
return(Fact(value));
}
private bool TryParseFactorialFactor(out AstNode node)
{
if (TryParsePrimary(out node))
{
if (IsNext(TokenType.Factorial))
{
node = new FactorialUnaryOperatorAstNode(Accept(), node);
}
}
return(node != null);
}
