pub fn incgamma(n: f64, z: Complex) -> Result<Complex>Expand description
Upper incomplete gamma function Gamma(n, z) = integral_z^infinity t^(n-1) e^-t dt.
The degree n is an integer or half-integer. The branch cut lies on the negative
real axis, and the sign of a zero Im z selects its side.
Upstream: treams.special.incgamma. Differences: |n| above 128 and non-finite z
give an error; treams runs one degree recurrence, while this function chooses among
four methods the one that keeps relative accuracy at z.