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