Merge pull request #95 from runarberg/master

Added the power method for rational numbers
This commit is contained in:
Alex Crichton 2015-05-18 08:42:22 -07:00
commit 0ab1010b10
1 changed files with 26 additions and 1 deletions

View File

@ -18,7 +18,7 @@ use std::fmt;
use std::ops::{Add, Div, Mul, Neg, Rem, Sub};
use std::str::FromStr;
use traits::{FromPrimitive, Float};
use traits::{FromPrimitive, Float, PrimInt};
use bigint::{BigInt, BigUint, Sign};
use {Num, Signed, Zero, One};
@ -184,6 +184,19 @@ impl<T: Clone + Integer + PartialOrd> Ratio<T> {
}
}
impl<T: Clone + Integer + PartialOrd + PrimInt> Ratio<T> {
/// Raises the ratio to the power of an exponent
#[inline]
pub fn pow(&self, expon: i32) -> Ratio<T> {
match expon.cmp(&0) {
cmp::Ordering::Equal => One::one(),
cmp::Ordering::Less => self.recip().pow(-expon),
cmp::Ordering::Greater => Ratio::new_raw(self.numer.pow(expon as u32),
self.denom.pow(expon as u32)),
}
}
}
impl Ratio<BigInt> {
/// Converts a float into a rational number.
pub fn from_float<T: Float>(f: T) -> Option<BigRational> {
@ -758,6 +771,18 @@ mod test {
assert_eq!(_NEG1_2 * _NEG1_2.recip(), _1);
}
#[test]
fn test_pow() {
assert_eq!(_1_2.pow(2), Ratio::new(1, 4));
assert_eq!(_1_2.pow(-2), Ratio::new(4, 1));
assert_eq!(_1.pow(1), _1);
assert_eq!(_NEG1_2.pow(2), _1_2.pow(2));
assert_eq!(_NEG1_2.pow(3), -_1_2.pow(3));
assert_eq!(_3_2.pow(0), _1);
assert_eq!(_3_2.pow(-1), _3_2.recip());
assert_eq!(_3_2.pow(3), Ratio::new(27, 8));
}
#[test]
fn test_to_from_str() {
fn test(r: Rational, s: String) {