Move abs_sub to FloatMath

This removes the need for libcore to depend on libm. `abs_sub` is not as useful for integers.

3 files changed, 23 insertions, 1 deletions

diff --git a/src/libstd/num/f32.rs b/src/libstd/num/f32.rs
index 175b1612b7e..6e2e8b8752f 100644
--- a/src/libstd/num/f32.rs
+++ b/src/libstd/num/f32.rs
@@ -109,6 +109,11 @@ impl FloatMath for f32 {
     }
 
     #[inline]
+    fn abs_sub(self, other: f32) -> f32 {
+        unsafe { cmath::fdimf(self, other) }
+    }
+
+    #[inline]
     fn cbrt(self) -> f32 {
         unsafe { cmath::cbrtf(self) }
     }
diff --git a/src/libstd/num/f64.rs b/src/libstd/num/f64.rs
index eb8e8db798c..591ca3486d2 100644
--- a/src/libstd/num/f64.rs
+++ b/src/libstd/num/f64.rs
@@ -117,6 +117,11 @@ impl FloatMath for f64 {
     }
 
     #[inline]
+    fn abs_sub(self, other: f64) -> f64 {
+        unsafe { cmath::fdim(self, other) }
+    }
+
+    #[inline]
     fn cbrt(self) -> f64 {
         unsafe { cmath::cbrt(self) }
     }
diff --git a/src/libstd/num/mod.rs b/src/libstd/num/mod.rs
index ffe162cbc64..3f8504f4553 100644
--- a/src/libstd/num/mod.rs
+++ b/src/libstd/num/mod.rs
@@ -21,7 +21,7 @@ use option::Option;
 #[cfg(test)] use fmt::Show;
 
 pub use core::num::{Num, div_rem, Zero, zero, One, one};
-pub use core::num::{Signed, abs, abs_sub, signum};
+pub use core::num::{Signed, abs, signum};
 pub use core::num::{Unsigned, pow, Bounded};
 pub use core::num::{Primitive, Int, Saturating};
 pub use core::num::{CheckedAdd, CheckedSub, CheckedMul, CheckedDiv};
@@ -58,6 +58,11 @@ pub trait FloatMath: Float {
     /// Returns the minimum of the two numbers.
     fn min(self, other: Self) -> Self;
 
+    /// The positive difference of two numbers. Returns `0.0` if the number is
+    /// less than or equal to `other`, otherwise the difference between`self`
+    /// and `other` is returned.
+    fn abs_sub(self, other: Self) -> Self;
+
     /// Take the cubic root of a number.
     fn cbrt(self) -> Self;
     /// Calculate the length of the hypotenuse of a right-angle triangle given
@@ -122,6 +127,13 @@ pub fn from_str_radix<T: FromStrRadix>(str: &str, radix: uint) -> Option<T> {
     FromStrRadix::from_str_radix(str, radix)
 }
 
+// DEPRECATED
+
+#[deprecated = "Use `FloatMath::abs_sub`"]
+pub fn abs_sub<T: FloatMath>(x: T, y: T) -> T {
+    x.abs_sub(y)
+}
+
 /// Helper function for testing numeric operations
 #[cfg(test)]
 pub fn test_num<T:Num + NumCast + Show>(ten: T, two: T) {