Merge #37

37: Add Inv and Pow traits. r=cuviper a=clarcharr

This is not a breaking change, and closes #34 and #38.

This doesn't add any impls for the other `num` crates, just floats with `std` enabled. The trait has to be added before those other crates can be updated.

src/lib.rs

@@ -33,13 +33,14 @@ pub use float::Float;
 pub use float::FloatConst;
 // pub use real::{FloatCore, Real}; // NOTE: Don't do this, it breaks `use num_traits::*;`.
 pub use identities::{Zero, One, zero, one};
+pub use ops::inv::Inv;
 pub use ops::checked::{CheckedAdd, CheckedSub, CheckedMul, CheckedDiv, CheckedShl, CheckedShr};
 pub use ops::wrapping::{WrappingAdd, WrappingMul, WrappingSub};
 pub use ops::saturating::Saturating;
 pub use sign::{Signed, Unsigned, abs, abs_sub, signum};
 pub use cast::{AsPrimitive, FromPrimitive, ToPrimitive, NumCast, cast};
 pub use int::PrimInt;
-pub use pow::{pow, checked_pow};
+pub use pow::{Pow, pow, checked_pow};
 
 pub mod identities;
 pub mod sign;

src/ops/inv.rs

@@ -0,0 +1,39 @@
+/// Unary operator for retrieving the multiplicative inverse, or reciprocal, of a value.
+pub trait Inv {
+    /// The result after applying the operator.
+    type Output;
+
+    /// Returns the multiplicative inverse of `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::f64::INFINITY;
+    /// use num_traits::Inv;
+    ///
+    /// assert_eq!(7.0.inv() * 7.0, 1.0);
+    /// assert_eq!((-0.0).inv(), -INFINITY);
+    /// ```
+    fn inv(self) -> Self::Output;
+}
+
+impl Inv for f32 {
+    type Output = f32;
+    #[inline]
+    fn inv(self) -> f32 { 1.0 / self }
+}
+impl Inv for f64 {
+    type Output = f64;
+    #[inline]
+    fn inv(self) -> f64 { 1.0 / self }
+}
+impl<'a> Inv for &'a f32 {
+    type Output = f32;
+    #[inline]
+    fn inv(self) -> f32 { 1.0 / *self }
+}
+impl<'a> Inv for &'a f64 {
+    type Output = f64;
+    #[inline]
+    fn inv(self) -> f64 { 1.0 / *self }
+}

src/ops/mod.rs

@@ -1,3 +1,4 @@
 pub mod saturating;
 pub mod checked;
 pub mod wrapping;
+pub mod inv;

src/pow.rs

@@ -1,6 +1,153 @@
 use core::ops::Mul;
+use core::num::Wrapping;
 use {One, CheckedMul};
 
+/// Binary operator for raising a value to a power.
+pub trait Pow<RHS> {
+    /// The result after applying the operator.
+    type Output;
+
+    /// Returns `self` to the power `rhs`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use num_traits::Pow;
+    /// assert_eq!(Pow::pow(10u32, 2u32), 100);
+    /// ```
+    fn pow(self, rhs: RHS) -> Self::Output;
+}
+
+macro_rules! pow_impl {
+    ($t:ty) => {
+        pow_impl!($t, u8);
+        pow_impl!($t, usize);
+
+        // FIXME: these should be possible
+        // pow_impl!($t, u16);
+        // pow_impl!($t, u32);
+        // pow_impl!($t, u64);
+    };
+    ($t:ty, $rhs:ty) => {
+        pow_impl!($t, $rhs, usize, pow);
+    };
+    ($t:ty, $rhs:ty, $desired_rhs:ty, $method:expr) => {
+        impl Pow<$rhs> for $t {
+            type Output = $t;
+            #[inline]
+            fn pow(self, rhs: $rhs) -> $t {
+                ($method)(self, <$desired_rhs>::from(rhs))
+            }
+        }
+
+        impl<'a> Pow<&'a $rhs> for $t {
+            type Output = $t;
+            #[inline]
+            fn pow(self, rhs: &'a $rhs) -> $t {
+                ($method)(self, <$desired_rhs>::from(*rhs))
+            }
+        }
+
+        impl<'a> Pow<$rhs> for &'a $t {
+            type Output = $t;
+            #[inline]
+            fn pow(self, rhs: $rhs) -> $t {
+                ($method)(*self, <$desired_rhs>::from(rhs))
+            }
+        }
+
+        impl<'a, 'b> Pow<&'a $rhs> for &'b $t {
+            type Output = $t;
+            #[inline]
+            fn pow(self, rhs: &'a $rhs) -> $t {
+                ($method)(*self, <$desired_rhs>::from(*rhs))
+            }
+        }
+    };
+}
+
+pow_impl!(u8, u8, u32, u8::pow);
+pow_impl!(u8, u16, u32, u8::pow);
+pow_impl!(u8, u32, u32, u8::pow);
+pow_impl!(u8, usize);
+pow_impl!(i8, u8, u32, i8::pow);
+pow_impl!(i8, u16, u32, i8::pow);
+pow_impl!(i8, u32, u32, i8::pow);
+pow_impl!(i8, usize);
+pow_impl!(u16, u8, u32, u16::pow);
+pow_impl!(u16, u16, u32, u16::pow);
+pow_impl!(u16, u32, u32, u16::pow);
+pow_impl!(u16, usize);
+pow_impl!(i16, u8, u32, i16::pow);
+pow_impl!(i16, u16, u32, i16::pow);
+pow_impl!(i16, u32, u32, i16::pow);
+pow_impl!(i16, usize);
+pow_impl!(u32, u8, u32, u32::pow);
+pow_impl!(u32, u16, u32, u32::pow);
+pow_impl!(u32, u32, u32, u32::pow);
+pow_impl!(u32, usize);
+pow_impl!(i32, u8, u32, i32::pow);
+pow_impl!(i32, u16, u32, i32::pow);
+pow_impl!(i32, u32, u32, i32::pow);
+pow_impl!(i32, usize);
+pow_impl!(u64, u8, u32, u64::pow);
+pow_impl!(u64, u16, u32, u64::pow);
+pow_impl!(u64, u32, u32, u64::pow);
+pow_impl!(u64, usize);
+pow_impl!(i64, u8, u32, i64::pow);
+pow_impl!(i64, u16, u32, i64::pow);
+pow_impl!(i64, u32, u32, i64::pow);
+pow_impl!(i64, usize);
+pow_impl!(usize, u8, u32, usize::pow);
+pow_impl!(usize, u16, u32, usize::pow);
+pow_impl!(usize, u32, u32, usize::pow);
+pow_impl!(usize, usize);
+pow_impl!(isize, u8, u32, isize::pow);
+pow_impl!(isize, u16, u32, isize::pow);
+pow_impl!(isize, u32, u32, isize::pow);
+pow_impl!(isize, usize);
+pow_impl!(Wrapping<u8>);
+pow_impl!(Wrapping<i8>);
+pow_impl!(Wrapping<u16>);
+pow_impl!(Wrapping<i16>);
+pow_impl!(Wrapping<u32>);
+pow_impl!(Wrapping<i32>);
+pow_impl!(Wrapping<u64>);
+pow_impl!(Wrapping<i64>);
+pow_impl!(Wrapping<usize>);
+pow_impl!(Wrapping<isize>);
+
+// FIXME: these should be possible
+// pow_impl!(u8, u64);
+// pow_impl!(i16, u64);
+// pow_impl!(i8, u64);
+// pow_impl!(u16, u64);
+// pow_impl!(u32, u64);
+// pow_impl!(i32, u64);
+// pow_impl!(u64, u64);
+// pow_impl!(i64, u64);
+// pow_impl!(usize, u64);
+// pow_impl!(isize, u64);
+
+#[cfg(feature = "std")]
+mod float_impls {
+    use super::Pow;
+
+    pow_impl!(f32, i8, i32, f32::powi);
+    pow_impl!(f32, u8, i32, f32::powi);
+    pow_impl!(f32, i16, i32, f32::powi);
+    pow_impl!(f32, u16, i32, f32::powi);
+    pow_impl!(f32, i32, i32, f32::powi);
+    pow_impl!(f64, i8, i32, f64::powi);
+    pow_impl!(f64, u8, i32, f64::powi);
+    pow_impl!(f64, i16, i32, f64::powi);
+    pow_impl!(f64, u16, i32, f64::powi);
+    pow_impl!(f64, i32, i32, f64::powi);
+    pow_impl!(f32, f32, f32, f32::powf);
+    pow_impl!(f64, f32, f64, f64::powf);
+    pow_impl!(f64, f64, f64, f64::powf);
+}
+
 /// Raises a value to the power of exp, using exponentiation by squaring.
 ///
 /// # Example