libcore/num: implement pow() as a trait method of Pow.

src/libcore/num/mod.rs

@@ -25,6 +25,8 @@ use mem::size_of;
 use ops::{Add, Sub, Mul, Div, Rem, Neg};
 use ops::{Not, BitAnd, BitOr, BitXor, Shl, Shr};
 use option::{Option, Some, None};
+use num;
+use clone;
 
 /// The base trait for numeric types
 pub trait Num: PartialEq + Zero + One
@@ -319,11 +321,19 @@ trait_impl!(Unsigned for uint u8 u16 u32 u64)
 ///
 /// assert_eq!(num::pow(2i, 4), 16);
 /// ```
-#[inline]
-pub fn pow<T: One + Mul<T, T>>(mut base: T, mut exp: uint) -> T {
-    if exp == 1 { base }
-    else {
-        let mut acc = one::<T>();
+pub trait Pow {
+    /// Calcurate self * self * ... * self (exp times).
+    fn pow(&self, mut exp: uint) -> Self;
+
+    /// Calcurate self * self.
+    fn sq(&self) -> Self;
+}
+
+impl<M: num::One + Mul<M, M> + clone::Clone> Pow for M {
+    #[inline]
+    fn pow(&self, mut exp: uint) -> M {
+        let mut base = self.clone();
+        let mut acc = num::one::<M>();
         while exp > 0 {
             if (exp & 1) == 1 {
                 acc = acc * base;
@@ -333,6 +343,12 @@ pub fn pow<T: One + Mul<T, T>>(mut base: T, mut exp: uint) -> T {
         }
         acc
     }
+
+    #[inline]
+    fn sq(&self) -> M {
+        let s = self.clone();
+        s * s
+    }
 }
 
 /// Numbers which have upper and lower bounds

src/libserialize/json.rs

@@ -199,7 +199,7 @@ use std::collections::{HashMap, TreeMap};
 use std::{char, f64, fmt, io, num, str};
 use std::io::MemWriter;
 use std::mem::{swap, transmute};
-use std::num::{FPNaN, FPInfinite};
+use std::num::{FPNaN, FPInfinite, Pow};
 use std::str::ScalarValue;
 use std::string;
 use std::vec::Vec;
@@ -1472,7 +1472,7 @@ impl<T: Iterator<char>> Parser<T> {
             }
         }
 
-        let exp = num::pow(10_f64, exp);
+        let exp = 10_f64.pow(exp);
         if neg_exp {
             res /= exp;
         } else {

src/libstd/num/mod.rs

@@ -23,7 +23,7 @@ use string::String;
 
 pub use core::num::{Num, div_rem, Zero, zero, One, one};
 pub use core::num::{Signed, abs, abs_sub, signum};
-pub use core::num::{Unsigned, pow, Bounded};
+pub use core::num::{Unsigned, Pow, Bounded};
 pub use core::num::{Primitive, Int, Saturating};
 pub use core::num::{CheckedAdd, CheckedSub, CheckedMul, CheckedDiv};
 pub use core::num::{cast, FromPrimitive, NumCast, ToPrimitive};

src/libstd/num/strconv.rs

@@ -15,9 +15,8 @@
 use char;
 use clone::Clone;
 use collections::{Collection, MutableSeq};
-use num::{NumCast, Zero, One, cast, Int};
+use num::{NumCast, Zero, One, Pow, cast, Int};
 use num::{Float, FPNaN, FPInfinite, ToPrimitive};
-use num;
 use ops::{Add, Sub, Mul, Div, Rem, Neg};
 use option::{None, Option, Some};
 use slice::{ImmutableSlice, MutableSlice};
@@ -736,9 +735,9 @@ pub fn from_str_bytes_common<T:NumCast+Zero+One+PartialEq+PartialOrd+Div<T,T>+
         match exp {
             Some(exp_pow) => {
                 multiplier = if exp_pow < 0 {
-                    _1 / num::pow(base, (-exp_pow.to_int().unwrap()) as uint)
+                    _1 / base.pow((-exp_pow.to_int().unwrap()) as uint)
                 } else {
-                    num::pow(base, exp_pow.to_int().unwrap() as uint)
+                    base.pow(exp_pow.to_int().unwrap() as uint)
                 }
             }
             None => return None // invalid exponent -> invalid number