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Address some of @cuviper's feedback

This commit is contained in:
Vinzent Steinberg 2017-03-20 10:14:01 +01:00
parent 8d235759dd
commit e486e6a981
1 changed files with 10 additions and 11 deletions
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21
integer/src/lib.rs
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@ -666,34 +666,33 @@ impl_integer_for_usize!(u64, test_integer_u64);
impl_integer_for_usize!(usize, test_integer_usize); impl_integer_for_usize!(usize, test_integer_usize);
/// An iterator over binomial coefficients. /// An iterator over binomial coefficients.
pub struct BinomialCoeff<T> { pub struct IterBinomial<T> {
a: T, a: T,
n: T, n: T,
k: T, k: T,
} }
impl<T> BinomialCoeff<T> impl<T> IterBinomial<T>
where T: Integer, where T: Integer,
{ {
/// For a given n, iterate over all binomial coefficients ((k, n - k), binomial(n, k)). /// For a given n, iterate over all binomial coefficients ((k, n - k), binomial(n, k)).
pub fn new(n: T) -> BinomialCoeff<T> { pub fn new(n: T) -> IterBinomial<T> {
BinomialCoeff { IterBinomial {
k: T::zero(), a: T::one(), n: n k: T::zero(), a: T::one(), n: n
} }
} }
} }
impl<T> Iterator for BinomialCoeff<T> impl<T> Iterator for IterBinomial<T>
where T: Integer + Clone, where T: Integer + Clone
for<'a> &'a T: std::cmp::PartialEq<&'a T>
{ {
type Item = ((T, T), T); type Item = ((T, T), T);
fn next(&mut self) -> Option<((T, T), T)> { fn next(&mut self) -> Option<((T, T), T)> {
if &self.k > &self.n { if self.k > self.n {
return None; return None;
} }
self.a = if &self.k != &T::zero() { self.a = if !self.k.is_zero() {
(self.a.clone() * (self.n.clone() - self.k.clone() + T::one())) / self.k.clone() (self.a.clone() * (self.n.clone() - self.k.clone() + T::one())) / self.k.clone()
} else { } else {
T::one() T::one()
@ -768,7 +767,7 @@ fn test_binomial_coeff() {
macro_rules! check_simple { macro_rules! check_simple {
($t:ty) => { { ($t:ty) => { {
let n: $t = 3; let n: $t = 3;
let c: Vec<_> = BinomialCoeff::new(n).collect(); let c: Vec<_> = IterBinomial::new(n).collect();
let expected = vec![((0, 3), 1), ((1, 2), 3), ((2, 1), 3), ((3, 0), 1)]; let expected = vec![((0, 3), 1), ((1, 2), 3), ((2, 1), 3), ((3, 0), 1)];
assert_eq!(c, expected); assert_eq!(c, expected);
} } } }
@ -786,7 +785,7 @@ fn test_binomial_coeff() {
macro_rules! check_binomial { macro_rules! check_binomial {
($t:ty, $n:expr) => { { ($t:ty, $n:expr) => { {
let n: $t = $n; let n: $t = $n;
let c: Vec<_> = BinomialCoeff::new(n).collect(); let c: Vec<_> = IterBinomial::new(n).collect();
for &((k, _), b) in &c { for &((k, _), b) in &c {
assert_eq!(b, binomial(n, k)); assert_eq!(b, binomial(n, k));
} }