sign

Returns 1.0 if x > 0, -0.0 if x = -0.0, +0.0 if x = +0.0, or -1.0 if x < 0. Returns 0.0 if x is a NaN.

template <typename F, typename return_t, detail::enable_if_t<(detail::builtin::is_genfloat<F>::value), int> >
return_t sign(const F x)

1. Returns 1.0 if x > 0, -0.0 if x = -0.0, +0.0 if x = +0.0, or -1.0 if x < 0. Returns 0.0 if x is a NaN.
   Parameters:
   • const F x