diff --git a/traits/src/float.rs b/traits/src/float.rs index 66c174c0fd..757be876e5 100644 --- a/traits/src/float.rs +++ b/traits/src/float.rs @@ -2,6 +2,9 @@ use std::mem; use std::ops::Neg; use std::num::FpCategory; +// Used for default implementation of `epsilon` +use std::f32; + use {Num, NumCast}; // FIXME: these doctests aren't actually helpful, because they're using and @@ -89,6 +92,25 @@ pub trait Float /// ``` fn min_positive_value() -> Self; + /// Returns epsilon, a small positive value. + /// + /// ``` + /// use num_traits::Float; + /// use std::f64; + /// + /// let x: f64 = Float::epsilon(); + /// + /// assert_eq!(x, f64::EPSILON); + /// ``` + /// + /// # Panics + /// + /// The default implementation will panic if `f32::EPSILON` cannot + /// be cast to `Self`. + fn epsilon() -> Self { + Self::from(f32::EPSILON).expect("Unable to cast from f32::EPSILON") + } + /// Returns the largest finite value that this type can represent. /// /// ``` @@ -936,6 +958,11 @@ macro_rules! float_impl { ::std::$T::MIN_POSITIVE } + #[inline] + fn epsilon() -> Self { + ::std::$T::EPSILON + } + #[inline] fn max_value() -> Self { ::std::$T::MAX