numaxiom 0.0.2

Lightweight numeric marker traits for ranges/signs plus constants and ops; std by default, no_std optional.
Documentation 
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/// Nth root helper.
///
/// Implementers should document domain restrictions (e.g., negative bases for
/// even roots) and how exceptional cases (NaN, infinity, panic) are surfaced.
pub trait Root<Exp = Self> {
    type Output;

    fn root(self, degree: Exp) -> Self::Output;
}

#[cfg(any(feature = "std", feature = "libm"))]
mod float_impls {
    use super::Root;

    #[inline]
    fn powf_f32(base: f32, exp: f32) -> f32 {
        #[cfg(feature = "libm")]
        {
            libm::powf(base, exp)
        }
        #[cfg(not(feature = "libm"))]
        {
            f32::powf(base, exp)
        }
    }

    #[inline]
    fn powf_f64(base: f64, exp: f64) -> f64 {
        #[cfg(feature = "libm")]
        {
            libm::pow(base, exp)
        }
        #[cfg(not(feature = "libm"))]
        {
            f64::powf(base, exp)
        }
    }

    macro_rules! impl_root_float_self {
        ($ty:ty, $powf:ident) => {
            impl Root<$ty> for $ty {
                type Output = $ty;

                #[inline]
                fn root(self, degree: $ty) -> Self::Output {
                    $powf(self, 1.0 / degree)
                }
            }
        };
    }

    macro_rules! impl_root_float_int {
        ($ty:ty, $powf:ident) => {
            impl Root<u32> for $ty {
                type Output = $ty;

                #[inline]
                fn root(self, degree: u32) -> Self::Output {
                    let degree = degree as $ty;
                    $powf(self, 1.0 / degree)
                }
            }
        };
    }

    impl_root_float_self!(f32, powf_f32);
    impl_root_float_self!(f64, powf_f64);
    impl_root_float_int!(f32, powf_f32);
    impl_root_float_int!(f64, powf_f64);
}