Feature gate: #![feature(float_gamma)]

This is a tracking issue for adding the gamma and log-gamma functions to f32 and f64 (tgammaf, tgamma, lgammaf_r, and lgamma_f from C).

Refs:

• Gamma function rfcs#864
• Gamma function #18271

Public API

impl f32 {
    pub fn gamma(self) -> f32;
    pub fn ln_gamma(self) -> (f32, i32);
}

impl f64 {
    pub fn gamma(self) -> f64;
    pub fn ln_gamma(self) -> (f64, i32);
}

Steps / History

• Implementation: Add gamma function to f32 and f64 #99747
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• MinGW's implementation appears to be buggy https://sourceforge.net/p/mingw-w64/bugs/517/. We hit this with 1760.9_f64 in Deduplicated float tests and unified in floats/mod.rs #148206 (comment).