factorialLn function
Computes the logarithmic factorial function x
-> ln(x
!) of an integer number > 0.
Implementation
double factorialLn(int x) {
if (x < 0) {
throw ArgumentError.value(x, 'x', messages.argumentPositive);
}
if (x <= 1) {
return 0.0;
}
if (x < _factorialCache.length) {
return log(_factorialCache[x]);
}
return gammaLn(x + 1.0);
}