Replace old pow_with_uint with the new pow func

There was an old and barely used implementation of pow, which expected
both parameters to be uint and required more traits to be implemented.
Since a new implementation for `pow` landed, I'm proposing to remove
this old impl in favor of the new one.

The benchmark shows that the new implementation is faster than the one
being removed:

test num::bench::bench_pow_function               ..bench:      9429 ns/iter (+/- 2055)
test num::bench::bench_pow_with_uint_function     ...bench:     28476 ns/iter (+/- 2202)

Author: flaper87

src/libextra/json.rs

@@ -688,7 +688,7 @@ impl<T : Iterator<char>> Parser<T> {
             }
         }
 
-        let exp: f64 = num::pow_with_uint(10u, exp);
+        let exp: f64 = num::pow(10u as f64, exp);
         if neg_exp {
             res /= exp;
         } else {

src/libstd/num/mod.rs

@@ -993,37 +993,6 @@ pub fn from_str_radix<T: FromStrRadix>(str: &str, radix: uint) -> Option<T> {
     FromStrRadix::from_str_radix(str, radix)
 }
 
-/// Calculates a power to a given radix, optimized for uint `pow` and `radix`.
-///
-/// Returns `radix^pow` as `T`.
-///
-/// Note:
-/// Also returns `1` for `0^0`, despite that technically being an
-/// undefined number. The reason for this is twofold:
-/// - If code written to use this function cares about that special case, it's
-///   probably going to catch it before making the call.
-/// - If code written to use this function doesn't care about it, it's
-///   probably assuming that `x^0` always equals `1`.
-///
-pub fn pow_with_uint<T:NumCast+One+Zero+Div<T,T>+Mul<T,T>>(radix: uint, pow: uint) -> T {
-    let _0: T = Zero::zero();
-    let _1: T = One::one();
-
-    if pow   == 0u { return _1; }
-    if radix == 0u { return _0; }
-    let mut my_pow     = pow;
-    let mut total      = _1;
-    let mut multiplier = cast(radix).unwrap();
-    while (my_pow > 0u) {
-        if my_pow % 2u == 1u {
-            total = total * multiplier;
-        }
-        my_pow = my_pow / 2u;
-        multiplier = multiplier * multiplier;
-    }
-    total
-}
-
 impl<T: Zero + 'static> Zero for @T {
     fn zero() -> @T { @Zero::zero() }
     fn is_zero(&self) -> bool { (**self).is_zero() }
@@ -1698,10 +1667,4 @@ mod bench {
         let v = vec::from_fn(1024, |n| n);
         b.iter(|| {v.iter().fold(0, |old, new| num::pow(old, *new));});
     }
-
-    #[bench]
-    fn bench_pow_with_uint_function(b: &mut BenchHarness) {
-        let v = vec::from_fn(1024, |n| n);
-        b.iter(|| {v.iter().fold(0, |old, new| num::pow_with_uint(old, *new));});
-    }
 }

src/libstd/num/strconv.rs

@@ -20,7 +20,8 @@ use str::{StrSlice};
 use str;
 use vec::{CopyableVector, ImmutableVector, MutableVector};
 use vec::OwnedVector;
-use num::{NumCast, Zero, One, cast, pow_with_uint, Integer};
+use num;
+use num::{NumCast, Zero, One, cast, Integer};
 use num::{Round, Float, FPNaN, FPInfinite, ToPrimitive};
 
 pub enum ExponentFormat {
@@ -648,10 +649,10 @@ pub fn from_str_bytes_common<T:NumCast+Zero+One+Eq+Ord+Div<T,T>+
 
     if exp_found {
         let c = buf[i] as char;
-        let base = match (c, exponent) {
+        let base: T = match (c, exponent) {
             // c is never _ so don't need to handle specially
-            ('e', ExpDec) | ('E', ExpDec) => 10u,
-            ('p', ExpBin) | ('P', ExpBin) => 2u,
+            ('e', ExpDec) | ('E', ExpDec) => cast(10u).unwrap(),
+            ('p', ExpBin) | ('P', ExpBin) => cast(2u).unwrap(),
             _ => return None // char doesn't fit given exponent format
         };
 
@@ -664,9 +665,9 @@ pub fn from_str_bytes_common<T:NumCast+Zero+One+Eq+Ord+Div<T,T>+
         match exp {
             Some(exp_pow) => {
                 multiplier = if exp_pow < 0 {
-                    _1 / pow_with_uint::<T>(base, (-exp_pow.to_int().unwrap()) as uint)
+                    _1 / num::pow(base, (-exp_pow.to_int().unwrap()) as uint)
                 } else {
-                    pow_with_uint::<T>(base, exp_pow.to_int().unwrap() as uint)
+                    num::pow(base, exp_pow.to_int().unwrap() as uint)
                 }
             }
             None => return None // invalid exponent -> invalid number