Function rgsl::exponential::exprel_e

pub fn exprel_e(x: f64) -> Result<Result, Value>

This routine computes the quantity (\exp(x)-1)/x using an algorithm that is accurate for small x. For small x the algorithm is based on the expansion (\exp(x)-1)/x = 1 + x/2 + x^2/(2*3) + x^3/(2*3*4) + \dots.