[Bug libstdc++/83833] chi_squared_distribution::param() forgot to change the member gamma_distribution

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83833

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Oh, we multiply by two in operator() instead. But is that equivalent?