Merge 269c141e46
into a415e2a751
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commit
4af6c0968a
35
src/pow.rs
35
src/pow.rs
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@ -1,6 +1,6 @@
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use core::num::Wrapping;
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use core::ops::Mul;
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use {CheckedMul, One};
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use {CheckedMul, One, Zero};
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/// Binary operator for raising a value to a power.
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pub trait Pow<RHS> {
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@ -172,6 +172,7 @@ mod float_impls {
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}
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/// Raises a value to the power of exp, using exponentiation by squaring.
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/// Panics if pow(0, 0) (0⁰ is undefined)
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///
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/// # Example
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///
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@ -182,9 +183,13 @@ mod float_impls {
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/// assert_eq!(pow(6u8, 3), 216);
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/// ```
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#[inline]
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pub fn pow<T: Clone + One + Mul<T, Output = T>>(mut base: T, mut exp: usize) -> T {
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pub fn pow<T: Clone + Zero + One + Mul<T, Output = T>>(mut base: T, mut exp: usize) -> T {
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if exp == 0 {
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return T::one();
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return if base.is_zero() {
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panic!("pow(0, 0) is undefined")
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} else {
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T::one()
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};
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}
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while exp & 1 == 0 {
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@ -207,6 +212,7 @@ pub fn pow<T: Clone + One + Mul<T, Output = T>>(mut base: T, mut exp: usize) ->
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}
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/// Raises a value to the power of exp, returning `None` if an overflow occurred.
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/// Also returns None if checked_pow(0, 0) was entered (0⁰ is undefined)
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///
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/// Otherwise same as the `pow` function.
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///
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@ -218,11 +224,12 @@ pub fn pow<T: Clone + One + Mul<T, Output = T>>(mut base: T, mut exp: usize) ->
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/// assert_eq!(checked_pow(2i8, 4), Some(16));
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/// assert_eq!(checked_pow(7i8, 8), None);
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/// assert_eq!(checked_pow(7u32, 8), Some(5_764_801));
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/// assert_eq!(checked_pow(0i8, 0), None); //undefined
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/// ```
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#[inline]
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pub fn checked_pow<T: Clone + One + CheckedMul>(mut base: T, mut exp: usize) -> Option<T> {
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pub fn checked_pow<T: Clone + Zero + One + CheckedMul>(mut base: T, mut exp: usize) -> Option<T> {
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if exp == 0 {
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return Some(T::one());
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return if base.is_zero() { None } else { Some(T::one()) };
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}
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macro_rules! optry {
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@ -253,3 +260,21 @@ pub fn checked_pow<T: Clone + One + CheckedMul>(mut base: T, mut exp: usize) ->
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}
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Some(acc)
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}
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#[cfg(test)]
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mod tests {
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#[test]
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fn pow_3_3() {
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assert_eq!(super::checked_pow(3, 3), Some(27));
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assert_eq!(super::pow(3, 3), 27);
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}
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#[test]
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fn checked_pow_0_0() {
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assert_eq!(super::checked_pow(0, 0), None);
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}
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#[test]
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#[should_panic]
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fn pow_0_0() {
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super::pow(0, 0);
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}
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}
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