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fuchsia / third_party / rust / 9f7b58f3c94708f344237f826b4f96a659b5fc82 / . / src / libcore / tests / iter.rs
blob: bd3218ec27f3212112f585a440970b830e2896fc [file] [log] [blame]
use core::cell::Cell;
use core::convert::TryFrom;
use core::iter::*;
use core::usize;
use core::{i16, i8, isize};
#[test]
fn test_lt() {
let empty: [isize; 0] = [];
let xs = [1, 2, 3];
let ys = [1, 2, 0];
assert!(!xs.iter().lt(ys.iter()));
assert!(!xs.iter().le(ys.iter()));
assert!(xs.iter().gt(ys.iter()));
assert!(xs.iter().ge(ys.iter()));
assert!(ys.iter().lt(xs.iter()));
assert!(ys.iter().le(xs.iter()));
assert!(!ys.iter().gt(xs.iter()));
assert!(!ys.iter().ge(xs.iter()));
assert!(empty.iter().lt(xs.iter()));
assert!(empty.iter().le(xs.iter()));
assert!(!empty.iter().gt(xs.iter()));
assert!(!empty.iter().ge(xs.iter()));
// Sequence with NaN
let u = [1.0f64, 2.0];
let v = [0.0f64 / 0.0, 3.0];
assert!(!u.iter().lt(v.iter()));
assert!(!u.iter().le(v.iter()));
assert!(!u.iter().gt(v.iter()));
assert!(!u.iter().ge(v.iter()));
let a = [0.0f64 / 0.0];
let b = [1.0f64];
let c = [2.0f64];
assert!(a.iter().lt(b.iter()) == (a[0] < b[0]));
assert!(a.iter().le(b.iter()) == (a[0] <= b[0]));
assert!(a.iter().gt(b.iter()) == (a[0] > b[0]));
assert!(a.iter().ge(b.iter()) == (a[0] >= b[0]));
assert!(c.iter().lt(b.iter()) == (c[0] < b[0]));
assert!(c.iter().le(b.iter()) == (c[0] <= b[0]));
assert!(c.iter().gt(b.iter()) == (c[0] > b[0]));
assert!(c.iter().ge(b.iter()) == (c[0] >= b[0]));
}
#[test]
fn test_multi_iter() {
let xs = [1, 2, 3, 4];
let ys = [4, 3, 2, 1];
assert!(xs.iter().eq(ys.iter().rev()));
assert!(xs.iter().lt(xs.iter().skip(2)));
}
#[test]
fn test_cmp_by() {
use core::cmp::Ordering;
let f = |x: i32, y: i32| (x * x).cmp(&y);
let xs = || [1, 2, 3, 4].iter().copied();
let ys = || [1, 4, 16].iter().copied();
assert_eq!(xs().cmp_by(ys(), f), Ordering::Less);
assert_eq!(ys().cmp_by(xs(), f), Ordering::Greater);
assert_eq!(xs().cmp_by(xs().map(|x| x * x), f), Ordering::Equal);
assert_eq!(xs().rev().cmp_by(ys().rev(), f), Ordering::Greater);
assert_eq!(xs().cmp_by(ys().rev(), f), Ordering::Less);
assert_eq!(xs().cmp_by(ys().take(2), f), Ordering::Greater);
}
#[test]
fn test_partial_cmp_by() {
use core::cmp::Ordering;
use core::f64;
let f = |x: i32, y: i32| (x * x).partial_cmp(&y);
let xs = || [1, 2, 3, 4].iter().copied();
let ys = || [1, 4, 16].iter().copied();
assert_eq!(xs().partial_cmp_by(ys(), f), Some(Ordering::Less));
assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
assert_eq!(xs().partial_cmp_by(xs().map(|x| x * x), f), Some(Ordering::Equal));
assert_eq!(xs().rev().partial_cmp_by(ys().rev(), f), Some(Ordering::Greater));
assert_eq!(xs().partial_cmp_by(xs().rev(), f), Some(Ordering::Less));
assert_eq!(xs().partial_cmp_by(ys().take(2), f), Some(Ordering::Greater));
let f = |x: f64, y: f64| (x * x).partial_cmp(&y);
let xs = || [1.0, 2.0, 3.0, 4.0].iter().copied();
let ys = || [1.0, 4.0, f64::NAN, 16.0].iter().copied();
assert_eq!(xs().partial_cmp_by(ys(), f), None);
assert_eq!(ys().partial_cmp_by(xs(), f), Some(Ordering::Greater));
}
#[test]
fn test_eq_by() {
let f = |x: i32, y: i32| x * x == y;
let xs = || [1, 2, 3, 4].iter().copied();
let ys = || [1, 4, 9, 16].iter().copied();
assert!(xs().eq_by(ys(), f));
assert!(!ys().eq_by(xs(), f));
assert!(!xs().eq_by(xs(), f));
assert!(!ys().eq_by(ys(), f));
assert!(!xs().take(3).eq_by(ys(), f));
assert!(!xs().eq_by(ys().take(3), f));
assert!(xs().take(3).eq_by(ys().take(3), f));
}
#[test]
fn test_counter_from_iter() {
let it = (0..).step_by(5).take(10);
let xs: Vec<isize> = FromIterator::from_iter(it);
assert_eq!(xs, [0, 5, 10, 15, 20, 25, 30, 35, 40, 45]);
}
#[test]
fn test_iterator_chain() {
let xs = [0, 1, 2, 3, 4, 5];
let ys = [30, 40, 50, 60];
let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
let it = xs.iter().chain(&ys);
let mut i = 0;
for &x in it {
assert_eq!(x, expected[i]);
i += 1;
}
assert_eq!(i, expected.len());
let ys = (30..).step_by(10).take(4);
let it = xs.iter().cloned().chain(ys);
let mut i = 0;
for x in it {
assert_eq!(x, expected[i]);
i += 1;
}
assert_eq!(i, expected.len());
}
#[test]
fn test_iterator_chain_nth() {
let xs = [0, 1, 2, 3, 4, 5];
let ys = [30, 40, 50, 60];
let zs = [];
let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
for (i, x) in expected.iter().enumerate() {
assert_eq!(Some(x), xs.iter().chain(&ys).nth(i));
}
assert_eq!(zs.iter().chain(&xs).nth(0), Some(&0));
let mut it = xs.iter().chain(&zs);
assert_eq!(it.nth(5), Some(&5));
assert_eq!(it.next(), None);
}
#[test]
fn test_iterator_chain_nth_back() {
let xs = [0, 1, 2, 3, 4, 5];
let ys = [30, 40, 50, 60];
let zs = [];
let expected = [0, 1, 2, 3, 4, 5, 30, 40, 50, 60];
for (i, x) in expected.iter().rev().enumerate() {
assert_eq!(Some(x), xs.iter().chain(&ys).nth_back(i));
}
assert_eq!(zs.iter().chain(&xs).nth_back(0), Some(&5));
let mut it = xs.iter().chain(&zs);
assert_eq!(it.nth_back(5), Some(&0));
assert_eq!(it.next(), None);
}
#[test]
fn test_iterator_chain_last() {
let xs = [0, 1, 2, 3, 4, 5];
let ys = [30, 40, 50, 60];
let zs = [];
assert_eq!(xs.iter().chain(&ys).last(), Some(&60));
assert_eq!(zs.iter().chain(&ys).last(), Some(&60));
assert_eq!(ys.iter().chain(&zs).last(), Some(&60));
assert_eq!(zs.iter().chain(&zs).last(), None);
}
#[test]
fn test_iterator_chain_count() {
let xs = [0, 1, 2, 3, 4, 5];
let ys = [30, 40, 50, 60];
let zs = [];
assert_eq!(xs.iter().chain(&ys).count(), 10);
assert_eq!(zs.iter().chain(&ys).count(), 4);
}
#[test]
fn test_iterator_chain_find() {
let xs = [0, 1, 2, 3, 4, 5];
let ys = [30, 40, 50, 60];
let mut iter = xs.iter().chain(&ys);
assert_eq!(iter.find(|&&i| i == 4), Some(&4));
assert_eq!(iter.next(), Some(&5));
assert_eq!(iter.find(|&&i| i == 40), Some(&40));
assert_eq!(iter.next(), Some(&50));
assert_eq!(iter.find(|&&i| i == 100), None);
assert_eq!(iter.next(), None);
}
#[test]
fn test_iterator_chain_size_hint() {
struct Iter {
is_empty: bool,
}
impl Iterator for Iter {
type Item = ();
// alternates between `None` and `Some(())`
fn next(&mut self) -> Option<Self::Item> {
if self.is_empty {
self.is_empty = false;
None
} else {
self.is_empty = true;
Some(())
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
if self.is_empty { (0, Some(0)) } else { (1, Some(1)) }
}
}
impl DoubleEndedIterator for Iter {
fn next_back(&mut self) -> Option<Self::Item> {
self.next()
}
}
// this chains an iterator of length 0 with an iterator of length 1,
// so after calling `.next()` once, the iterator is empty and the
// state is `ChainState::Back`. `.size_hint()` should now disregard
// the size hint of the left iterator
let mut iter = Iter { is_empty: true }.chain(once(()));
assert_eq!(iter.next(), Some(()));
assert_eq!(iter.size_hint(), (0, Some(0)));
let mut iter = once(()).chain(Iter { is_empty: true });
assert_eq!(iter.next_back(), Some(()));
assert_eq!(iter.size_hint(), (0, Some(0)));
}
#[test]
fn test_zip_nth() {
let xs = [0, 1, 2, 4, 5];
let ys = [10, 11, 12];
let mut it = xs.iter().zip(&ys);
assert_eq!(it.nth(0), Some((&0, &10)));
assert_eq!(it.nth(1), Some((&2, &12)));
assert_eq!(it.nth(0), None);
let mut it = xs.iter().zip(&ys);
assert_eq!(it.nth(3), None);
let mut it = ys.iter().zip(&xs);
assert_eq!(it.nth(3), None);
}
#[test]
fn test_zip_nth_side_effects() {
let mut a = Vec::new();
let mut b = Vec::new();
let value = [1, 2, 3, 4, 5, 6]
.iter()
.cloned()
.map(|n| {
a.push(n);
n * 10
})
.zip([2, 3, 4, 5, 6, 7, 8].iter().cloned().map(|n| {
b.push(n * 100);
n * 1000
}))
.skip(1)
.nth(3);
assert_eq!(value, Some((50, 6000)));
assert_eq!(a, vec![1, 2, 3, 4, 5]);
assert_eq!(b, vec![200, 300, 400, 500, 600]);
}
#[test]
fn test_iterator_step_by() {
// Identity
let mut it = (0..).step_by(1).take(3);
assert_eq!(it.next(), Some(0));
assert_eq!(it.next(), Some(1));
assert_eq!(it.next(), Some(2));
assert_eq!(it.next(), None);
let mut it = (0..).step_by(3).take(4);
assert_eq!(it.next(), Some(0));
assert_eq!(it.next(), Some(3));
assert_eq!(it.next(), Some(6));
assert_eq!(it.next(), Some(9));
assert_eq!(it.next(), None);
let mut it = (0..3).step_by(1);
assert_eq!(it.next_back(), Some(2));
assert_eq!(it.next_back(), Some(1));
assert_eq!(it.next_back(), Some(0));
assert_eq!(it.next_back(), None);
let mut it = (0..11).step_by(3);
assert_eq!(it.next_back(), Some(9));
assert_eq!(it.next_back(), Some(6));
assert_eq!(it.next_back(), Some(3));
assert_eq!(it.next_back(), Some(0));
assert_eq!(it.next_back(), None);
}
#[test]
fn test_iterator_step_by_nth() {
let mut it = (0..16).step_by(5);
assert_eq!(it.nth(0), Some(0));
assert_eq!(it.nth(0), Some(5));
assert_eq!(it.nth(0), Some(10));
assert_eq!(it.nth(0), Some(15));
assert_eq!(it.nth(0), None);
let it = (0..18).step_by(5);
assert_eq!(it.clone().nth(0), Some(0));
assert_eq!(it.clone().nth(1), Some(5));
assert_eq!(it.clone().nth(2), Some(10));
assert_eq!(it.clone().nth(3), Some(15));
assert_eq!(it.clone().nth(4), None);
assert_eq!(it.clone().nth(42), None);
}
#[test]
fn test_iterator_step_by_nth_overflow() {
#[cfg(target_pointer_width = "8")]
type Bigger = u16;
#[cfg(target_pointer_width = "16")]
type Bigger = u32;
#[cfg(target_pointer_width = "32")]
type Bigger = u64;
#[cfg(target_pointer_width = "64")]
type Bigger = u128;
#[derive(Clone)]
struct Test(Bigger);
impl Iterator for &mut Test {
type Item = i32;
fn next(&mut self) -> Option<Self::Item> {
Some(21)
}
fn nth(&mut self, n: usize) -> Option<Self::Item> {
self.0 += n as Bigger + 1;
Some(42)
}
}
let mut it = Test(0);
let root = usize::MAX >> (::std::mem::size_of::<usize>() * 8 / 2);
let n = root + 20;
(&mut it).step_by(n).nth(n);
assert_eq!(it.0, n as Bigger * n as Bigger);
// large step
let mut it = Test(0);
(&mut it).step_by(usize::MAX).nth(5);
assert_eq!(it.0, (usize::MAX as Bigger) * 5);
// n + 1 overflows
let mut it = Test(0);
(&mut it).step_by(2).nth(usize::MAX);
assert_eq!(it.0, (usize::MAX as Bigger) * 2);
// n + 1 overflows
let mut it = Test(0);
(&mut it).step_by(1).nth(usize::MAX);
assert_eq!(it.0, (usize::MAX as Bigger) * 1);
}
#[test]
fn test_iterator_step_by_nth_try_fold() {
let mut it = (0..).step_by(10);
assert_eq!(it.try_fold(0, i8::checked_add), None);
assert_eq!(it.next(), Some(60));
assert_eq!(it.try_fold(0, i8::checked_add), None);
assert_eq!(it.next(), Some(90));
let mut it = (100..).step_by(10);
assert_eq!(it.try_fold(50, i8::checked_add), None);
assert_eq!(it.next(), Some(110));
let mut it = (100..=100).step_by(10);
assert_eq!(it.next(), Some(100));
assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
}
#[test]
fn test_iterator_step_by_nth_back() {
let mut it = (0..16).step_by(5);
assert_eq!(it.nth_back(0), Some(15));
assert_eq!(it.nth_back(0), Some(10));
assert_eq!(it.nth_back(0), Some(5));
assert_eq!(it.nth_back(0), Some(0));
assert_eq!(it.nth_back(0), None);
let mut it = (0..16).step_by(5);
assert_eq!(it.next(), Some(0)); // to set `first_take` to `false`
assert_eq!(it.nth_back(0), Some(15));
assert_eq!(it.nth_back(0), Some(10));
assert_eq!(it.nth_back(0), Some(5));
assert_eq!(it.nth_back(0), None);
let it = || (0..18).step_by(5);
assert_eq!(it().nth_back(0), Some(15));
assert_eq!(it().nth_back(1), Some(10));
assert_eq!(it().nth_back(2), Some(5));
assert_eq!(it().nth_back(3), Some(0));
assert_eq!(it().nth_back(4), None);
assert_eq!(it().nth_back(42), None);
}
#[test]
fn test_iterator_step_by_nth_try_rfold() {
let mut it = (0..100).step_by(10);
assert_eq!(it.try_rfold(0, i8::checked_add), None);
assert_eq!(it.next_back(), Some(70));
assert_eq!(it.next(), Some(0));
assert_eq!(it.try_rfold(0, i8::checked_add), None);
assert_eq!(it.next_back(), Some(30));
let mut it = (0..100).step_by(10);
assert_eq!(it.try_rfold(50, i8::checked_add), None);
assert_eq!(it.next_back(), Some(80));
let mut it = (100..=100).step_by(10);
assert_eq!(it.next_back(), Some(100));
assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
}
#[test]
#[should_panic]
fn test_iterator_step_by_zero() {
let mut it = (0..).step_by(0);
it.next();
}
#[test]
fn test_iterator_step_by_size_hint() {
struct StubSizeHint(usize, Option<usize>);
impl Iterator for StubSizeHint {
type Item = ();
fn next(&mut self) -> Option<()> {
self.0 -= 1;
if let Some(ref mut upper) = self.1 {
*upper -= 1;
}
Some(())
}
fn size_hint(&self) -> (usize, Option<usize>) {
(self.0, self.1)
}
}
// The two checks in each case are needed because the logic
// is different before the first call to `next()`.
let mut it = StubSizeHint(10, Some(10)).step_by(1);
assert_eq!(it.size_hint(), (10, Some(10)));
it.next();
assert_eq!(it.size_hint(), (9, Some(9)));
// exact multiple
let mut it = StubSizeHint(10, Some(10)).step_by(3);
assert_eq!(it.size_hint(), (4, Some(4)));
it.next();
assert_eq!(it.size_hint(), (3, Some(3)));
// larger base range, but not enough to get another element
let mut it = StubSizeHint(12, Some(12)).step_by(3);
assert_eq!(it.size_hint(), (4, Some(4)));
it.next();
assert_eq!(it.size_hint(), (3, Some(3)));
// smaller base range, so fewer resulting elements
let mut it = StubSizeHint(9, Some(9)).step_by(3);
assert_eq!(it.size_hint(), (3, Some(3)));
it.next();
assert_eq!(it.size_hint(), (2, Some(2)));
// infinite upper bound
let mut it = StubSizeHint(usize::MAX, None).step_by(1);
assert_eq!(it.size_hint(), (usize::MAX, None));
it.next();
assert_eq!(it.size_hint(), (usize::MAX - 1, None));
// still infinite with larger step
let mut it = StubSizeHint(7, None).step_by(3);
assert_eq!(it.size_hint(), (3, None));
it.next();
assert_eq!(it.size_hint(), (2, None));
// propagates ExactSizeIterator
let a = [1, 2, 3, 4, 5];
let it = a.iter().step_by(2);
assert_eq!(it.len(), 3);
// Cannot be TrustedLen as a step greater than one makes an iterator
// with (usize::MAX, None) no longer meet the safety requirements
trait TrustedLenCheck {
fn test(self) -> bool;
}
impl<T: Iterator> TrustedLenCheck for T {
default fn test(self) -> bool {
false
}
}
impl<T: TrustedLen> TrustedLenCheck for T {
fn test(self) -> bool {
true
}
}
assert!(TrustedLenCheck::test(a.iter()));
assert!(!TrustedLenCheck::test(a.iter().step_by(1)));
}
#[test]
fn test_filter_map() {
let it = (0..).step_by(1).take(10).filter_map(|x| if x % 2 == 0 { Some(x * x) } else { None });
assert_eq!(it.collect::<Vec<usize>>(), [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8]);
}
#[test]
fn test_filter_map_fold() {
let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
let ys = [0 * 0, 2 * 2, 4 * 4, 6 * 6, 8 * 8];
let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None });
let i = it.fold(0, |i, x| {
assert_eq!(x, ys[i]);
i + 1
});
assert_eq!(i, ys.len());
let it = xs.iter().filter_map(|&x| if x % 2 == 0 { Some(x * x) } else { None });
let i = it.rfold(ys.len(), |i, x| {
assert_eq!(x, ys[i - 1]);
i - 1
});
assert_eq!(i, 0);
}
#[test]
fn test_iterator_enumerate() {
let xs = [0, 1, 2, 3, 4, 5];
let it = xs.iter().enumerate();
for (i, &x) in it {
assert_eq!(i, x);
}
}
#[test]
fn test_iterator_enumerate_nth() {
let xs = [0, 1, 2, 3, 4, 5];
for (i, &x) in xs.iter().enumerate() {
assert_eq!(i, x);
}
let mut it = xs.iter().enumerate();
while let Some((i, &x)) = it.nth(0) {
assert_eq!(i, x);
}
let mut it = xs.iter().enumerate();
while let Some((i, &x)) = it.nth(1) {
assert_eq!(i, x);
}
let (i, &x) = xs.iter().enumerate().nth(3).unwrap();
assert_eq!(i, x);
assert_eq!(i, 3);
}
#[test]
fn test_iterator_enumerate_nth_back() {
let xs = [0, 1, 2, 3, 4, 5];
let mut it = xs.iter().enumerate();
while let Some((i, &x)) = it.nth_back(0) {
assert_eq!(i, x);
}
let mut it = xs.iter().enumerate();
while let Some((i, &x)) = it.nth_back(1) {
assert_eq!(i, x);
}
let (i, &x) = xs.iter().enumerate().nth_back(3).unwrap();
assert_eq!(i, x);
assert_eq!(i, 2);
}
#[test]
fn test_iterator_enumerate_count() {
let xs = [0, 1, 2, 3, 4, 5];
assert_eq!(xs.iter().enumerate().count(), 6);
}
#[test]
fn test_iterator_enumerate_fold() {
let xs = [0, 1, 2, 3, 4, 5];
let mut it = xs.iter().enumerate();
// steal a couple to get an interesting offset
assert_eq!(it.next(), Some((0, &0)));
assert_eq!(it.next(), Some((1, &1)));
let i = it.fold(2, |i, (j, &x)| {
assert_eq!(i, j);
assert_eq!(x, xs[j]);
i + 1
});
assert_eq!(i, xs.len());
let mut it = xs.iter().enumerate();
assert_eq!(it.next(), Some((0, &0)));
let i = it.rfold(xs.len() - 1, |i, (j, &x)| {
assert_eq!(i, j);
assert_eq!(x, xs[j]);
i - 1
});
assert_eq!(i, 0);
}
#[test]
fn test_iterator_filter_count() {
let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
assert_eq!(xs.iter().filter(|&&x| x % 2 == 0).count(), 5);
}
#[test]
fn test_iterator_filter_fold() {
let xs = [0, 1, 2, 3, 4, 5, 6, 7, 8];
let ys = [0, 2, 4, 6, 8];
let it = xs.iter().filter(|&&x| x % 2 == 0);
let i = it.fold(0, |i, &x| {
assert_eq!(x, ys[i]);
i + 1
});
assert_eq!(i, ys.len());
let it = xs.iter().filter(|&&x| x % 2 == 0);
let i = it.rfold(ys.len(), |i, &x| {
assert_eq!(x, ys[i - 1]);
i - 1
});
assert_eq!(i, 0);
}
#[test]
fn test_iterator_peekable() {
let xs = vec![0, 1, 2, 3, 4, 5];
let mut it = xs.iter().cloned().peekable();
assert_eq!(it.len(), 6);
assert_eq!(it.peek().unwrap(), &0);
assert_eq!(it.len(), 6);
assert_eq!(it.next().unwrap(), 0);
assert_eq!(it.len(), 5);
assert_eq!(it.next().unwrap(), 1);
assert_eq!(it.len(), 4);
assert_eq!(it.next().unwrap(), 2);
assert_eq!(it.len(), 3);
assert_eq!(it.peek().unwrap(), &3);
assert_eq!(it.len(), 3);
assert_eq!(it.peek().unwrap(), &3);
assert_eq!(it.len(), 3);
assert_eq!(it.next().unwrap(), 3);
assert_eq!(it.len(), 2);
assert_eq!(it.next().unwrap(), 4);
assert_eq!(it.len(), 1);
assert_eq!(it.peek().unwrap(), &5);
assert_eq!(it.len(), 1);
assert_eq!(it.next().unwrap(), 5);
assert_eq!(it.len(), 0);
assert!(it.peek().is_none());
assert_eq!(it.len(), 0);
assert!(it.next().is_none());
assert_eq!(it.len(), 0);
let mut it = xs.iter().cloned().peekable();
assert_eq!(it.len(), 6);
assert_eq!(it.peek().unwrap(), &0);
assert_eq!(it.len(), 6);
assert_eq!(it.next_back().unwrap(), 5);
assert_eq!(it.len(), 5);
assert_eq!(it.next_back().unwrap(), 4);
assert_eq!(it.len(), 4);
assert_eq!(it.next_back().unwrap(), 3);
assert_eq!(it.len(), 3);
assert_eq!(it.peek().unwrap(), &0);
assert_eq!(it.len(), 3);
assert_eq!(it.peek().unwrap(), &0);
assert_eq!(it.len(), 3);
assert_eq!(it.next_back().unwrap(), 2);
assert_eq!(it.len(), 2);
assert_eq!(it.next_back().unwrap(), 1);
assert_eq!(it.len(), 1);
assert_eq!(it.peek().unwrap(), &0);
assert_eq!(it.len(), 1);
assert_eq!(it.next_back().unwrap(), 0);
assert_eq!(it.len(), 0);
assert!(it.peek().is_none());
assert_eq!(it.len(), 0);
assert!(it.next_back().is_none());
assert_eq!(it.len(), 0);
}
#[test]
fn test_iterator_peekable_count() {
let xs = [0, 1, 2, 3, 4, 5];
let ys = [10];
let zs: [i32; 0] = [];
assert_eq!(xs.iter().peekable().count(), 6);
let mut it = xs.iter().peekable();
assert_eq!(it.peek(), Some(&&0));
assert_eq!(it.count(), 6);
assert_eq!(ys.iter().peekable().count(), 1);
let mut it = ys.iter().peekable();
assert_eq!(it.peek(), Some(&&10));
assert_eq!(it.count(), 1);
assert_eq!(zs.iter().peekable().count(), 0);
let mut it = zs.iter().peekable();
assert_eq!(it.peek(), None);
}
#[test]
fn test_iterator_peekable_nth() {
let xs = [0, 1, 2, 3, 4, 5];
let mut it = xs.iter().peekable();
assert_eq!(it.peek(), Some(&&0));
assert_eq!(it.nth(0), Some(&0));
assert_eq!(it.peek(), Some(&&1));
assert_eq!(it.nth(1), Some(&2));
assert_eq!(it.peek(), Some(&&3));
assert_eq!(it.nth(2), Some(&5));
assert_eq!(it.next(), None);
}
#[test]
fn test_iterator_peekable_last() {
let xs = [0, 1, 2, 3, 4, 5];
let ys = [0];
let mut it = xs.iter().peekable();
assert_eq!(it.peek(), Some(&&0));
assert_eq!(it.last(), Some(&5));
let mut it = ys.iter().peekable();
assert_eq!(it.peek(), Some(&&0));
assert_eq!(it.last(), Some(&0));
let mut it = ys.iter().peekable();
assert_eq!(it.next(), Some(&0));
assert_eq!(it.peek(), None);
assert_eq!(it.last(), None);
}
#[test]
fn test_iterator_peekable_fold() {
let xs = [0, 1, 2, 3, 4, 5];
let mut it = xs.iter().peekable();
assert_eq!(it.peek(), Some(&&0));
let i = it.fold(0, |i, &x| {
assert_eq!(x, xs[i]);
i + 1
});
assert_eq!(i, xs.len());
}
#[test]
fn test_iterator_peekable_rfold() {
let xs = [0, 1, 2, 3, 4, 5];
let mut it = xs.iter().peekable();
assert_eq!(it.peek(), Some(&&0));
let i = it.rfold(0, |i, &x| {
assert_eq!(x, xs[xs.len() - 1 - i]);
i + 1
});
assert_eq!(i, xs.len());
}
/// This is an iterator that follows the Iterator contract,
/// but it is not fused. After having returned None once, it will start
/// producing elements if .next() is called again.
pub struct CycleIter<'a, T> {
index: usize,
data: &'a [T],
}
pub fn cycle<T>(data: &[T]) -> CycleIter<'_, T> {
CycleIter { index: 0, data }
}
impl<'a, T> Iterator for CycleIter<'a, T> {
type Item = &'a T;
fn next(&mut self) -> Option<Self::Item> {
let elt = self.data.get(self.index);
self.index += 1;
self.index %= 1 + self.data.len();
elt
}
}
#[test]
fn test_iterator_peekable_remember_peek_none_1() {
// Check that the loop using .peek() terminates
let data = [1, 2, 3];
let mut iter = cycle(&data).peekable();
let mut n = 0;
while let Some(_) = iter.next() {
let is_the_last = iter.peek().is_none();
assert_eq!(is_the_last, n == data.len() - 1);
n += 1;
if n > data.len() {
break;
}
}
assert_eq!(n, data.len());
}
#[test]
fn test_iterator_peekable_remember_peek_none_2() {
let data = [0];
let mut iter = cycle(&data).peekable();
iter.next();
assert_eq!(iter.peek(), None);
assert_eq!(iter.last(), None);
}
#[test]
fn test_iterator_peekable_remember_peek_none_3() {
let data = [0];
let mut iter = cycle(&data).peekable();
iter.peek();
assert_eq!(iter.nth(0), Some(&0));
let mut iter = cycle(&data).peekable();
iter.next();
assert_eq!(iter.peek(), None);
assert_eq!(iter.nth(0), None);
}
#[test]
fn test_iterator_take_while() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
let ys = [0, 1, 2, 3, 5, 13];
let it = xs.iter().take_while(|&x| *x < 15);
let mut i = 0;
for x in it {
assert_eq!(*x, ys[i]);
i += 1;
}
assert_eq!(i, ys.len());
}
#[test]
fn test_iterator_skip_while() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
let ys = [15, 16, 17, 19];
let it = xs.iter().skip_while(|&x| *x < 15);
let mut i = 0;
for x in it {
assert_eq!(*x, ys[i]);
i += 1;
}
assert_eq!(i, ys.len());
}
#[test]
fn test_iterator_skip_while_fold() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
let ys = [15, 16, 17, 19];
let it = xs.iter().skip_while(|&x| *x < 15);
let i = it.fold(0, |i, &x| {
assert_eq!(x, ys[i]);
i + 1
});
assert_eq!(i, ys.len());
let mut it = xs.iter().skip_while(|&x| *x < 15);
assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
let i = it.fold(1, |i, &x| {
assert_eq!(x, ys[i]);
i + 1
});
assert_eq!(i, ys.len());
}
#[test]
fn test_iterator_skip() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
let ys = [13, 15, 16, 17, 19, 20, 30];
let mut it = xs.iter().skip(5);
let mut i = 0;
while let Some(&x) = it.next() {
assert_eq!(x, ys[i]);
i += 1;
assert_eq!(it.len(), xs.len() - 5 - i);
}
assert_eq!(i, ys.len());
assert_eq!(it.len(), 0);
}
#[test]
fn test_iterator_skip_doubleended() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
let mut it = xs.iter().rev().skip(5);
assert_eq!(it.next(), Some(&15));
assert_eq!(it.by_ref().rev().next(), Some(&0));
assert_eq!(it.next(), Some(&13));
assert_eq!(it.by_ref().rev().next(), Some(&1));
assert_eq!(it.next(), Some(&5));
assert_eq!(it.by_ref().rev().next(), Some(&2));
assert_eq!(it.next(), Some(&3));
assert_eq!(it.next(), None);
let mut it = xs.iter().rev().skip(5).rev();
assert_eq!(it.next(), Some(&0));
assert_eq!(it.rev().next(), Some(&15));
let mut it_base = xs.iter();
{
let mut it = it_base.by_ref().skip(5).rev();
assert_eq!(it.next(), Some(&30));
assert_eq!(it.next(), Some(&20));
assert_eq!(it.next(), Some(&19));
assert_eq!(it.next(), Some(&17));
assert_eq!(it.next(), Some(&16));
assert_eq!(it.next(), Some(&15));
assert_eq!(it.next(), Some(&13));
assert_eq!(it.next(), None);
}
// make sure the skipped parts have not been consumed
assert_eq!(it_base.next(), Some(&0));
assert_eq!(it_base.next(), Some(&1));
assert_eq!(it_base.next(), Some(&2));
assert_eq!(it_base.next(), Some(&3));
assert_eq!(it_base.next(), Some(&5));
assert_eq!(it_base.next(), None);
let it = xs.iter().skip(5).rev();
assert_eq!(it.last(), Some(&13));
}
#[test]
fn test_iterator_skip_nth() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
let mut it = xs.iter().skip(0);
assert_eq!(it.nth(0), Some(&0));
assert_eq!(it.nth(1), Some(&2));
let mut it = xs.iter().skip(5);
assert_eq!(it.nth(0), Some(&13));
assert_eq!(it.nth(1), Some(&16));
let mut it = xs.iter().skip(12);
assert_eq!(it.nth(0), None);
}
#[test]
fn test_iterator_skip_count() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
assert_eq!(xs.iter().skip(0).count(), 12);
assert_eq!(xs.iter().skip(1).count(), 11);
assert_eq!(xs.iter().skip(11).count(), 1);
assert_eq!(xs.iter().skip(12).count(), 0);
assert_eq!(xs.iter().skip(13).count(), 0);
}
#[test]
fn test_iterator_skip_last() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
assert_eq!(xs.iter().skip(0).last(), Some(&30));
assert_eq!(xs.iter().skip(1).last(), Some(&30));
assert_eq!(xs.iter().skip(11).last(), Some(&30));
assert_eq!(xs.iter().skip(12).last(), None);
assert_eq!(xs.iter().skip(13).last(), None);
let mut it = xs.iter().skip(5);
assert_eq!(it.next(), Some(&13));
assert_eq!(it.last(), Some(&30));
}
#[test]
fn test_iterator_skip_fold() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19, 20, 30];
let ys = [13, 15, 16, 17, 19, 20, 30];
let it = xs.iter().skip(5);
let i = it.fold(0, |i, &x| {
assert_eq!(x, ys[i]);
i + 1
});
assert_eq!(i, ys.len());
let mut it = xs.iter().skip(5);
assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
let i = it.fold(1, |i, &x| {
assert_eq!(x, ys[i]);
i + 1
});
assert_eq!(i, ys.len());
let it = xs.iter().skip(5);
let i = it.rfold(ys.len(), |i, &x| {
let i = i - 1;
assert_eq!(x, ys[i]);
i
});
assert_eq!(i, 0);
let mut it = xs.iter().skip(5);
assert_eq!(it.next(), Some(&ys[0])); // process skips before folding
let i = it.rfold(ys.len(), |i, &x| {
let i = i - 1;
assert_eq!(x, ys[i]);
i
});
assert_eq!(i, 1);
}
#[test]
fn test_iterator_take() {
let xs = [0, 1, 2, 3, 5, 13, 15, 16, 17, 19];
let ys = [0, 1, 2, 3, 5];
let mut it = xs.iter().take(ys.len());
let mut i = 0;
assert_eq!(it.len(), ys.len());
while let Some(&x) = it.next() {
assert_eq!(x, ys[i]);
i += 1;
assert_eq!(it.len(), ys.len() - i);
}
assert_eq!(i, ys.len());
assert_eq!(it.len(), 0);
let mut it = xs.iter().take(ys.len());
let mut i = 0;
assert_eq!(it.len(), ys.len());
while let Some(&x) = it.next_back() {
i += 1;
assert_eq!(x, ys[ys.len() - i]);
assert_eq!(it.len(), ys.len() - i);
}
assert_eq!(i, ys.len());
assert_eq!(it.len(), 0);
}
#[test]
fn test_iterator_take_nth() {
let xs = [0, 1, 2, 4, 5];
let mut it = xs.iter();
{
let mut take = it.by_ref().take(3);
let mut i = 0;
while let Some(&x) = take.nth(0) {
assert_eq!(x, i);
i += 1;
}
}
assert_eq!(it.nth(1), Some(&5));
assert_eq!(it.nth(0), None);
let xs = [0, 1, 2, 3, 4];
let mut it = xs.iter().take(7);
let mut i = 1;
while let Some(&x) = it.nth(1) {
assert_eq!(x, i);
i += 2;
}
}
#[test]
fn test_iterator_take_nth_back() {
let xs = [0, 1, 2, 4, 5];
let mut it = xs.iter();
{
let mut take = it.by_ref().take(3);
let mut i = 0;
while let Some(&x) = take.nth_back(0) {
i += 1;
assert_eq!(x, 3 - i);
}
}
assert_eq!(it.nth_back(0), None);
let xs = [0, 1, 2, 3, 4];
let mut it = xs.iter().take(7);
assert_eq!(it.nth_back(1), Some(&3));
assert_eq!(it.nth_back(1), Some(&1));
assert_eq!(it.nth_back(1), None);
}
#[test]
fn test_iterator_take_short() {
let xs = [0, 1, 2, 3];
let mut it = xs.iter().take(5);
let mut i = 0;
assert_eq!(it.len(), xs.len());
while let Some(&x) = it.next() {
assert_eq!(x, xs[i]);
i += 1;
assert_eq!(it.len(), xs.len() - i);
}
assert_eq!(i, xs.len());
assert_eq!(it.len(), 0);
let mut it = xs.iter().take(5);
let mut i = 0;
assert_eq!(it.len(), xs.len());
while let Some(&x) = it.next_back() {
i += 1;
assert_eq!(x, xs[xs.len() - i]);
assert_eq!(it.len(), xs.len() - i);
}
assert_eq!(i, xs.len());
assert_eq!(it.len(), 0);
}
#[test]
fn test_iterator_scan() {
// test the type inference
fn add(old: &mut isize, new: &usize) -> Option<f64> {
*old += *new as isize;
Some(*old as f64)
}
let xs = [0, 1, 2, 3, 4];
let ys = [0f64, 1.0, 3.0, 6.0, 10.0];
let it = xs.iter().scan(0, add);
let mut i = 0;
for x in it {
assert_eq!(x, ys[i]);
i += 1;
}
assert_eq!(i, ys.len());
}
#[test]
fn test_iterator_flat_map() {
let xs = [0, 3, 6];
let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
let it = xs.iter().flat_map(|&x| (x..).step_by(1).take(3));
let mut i = 0;
for x in it {
assert_eq!(x, ys[i]);
i += 1;
}
assert_eq!(i, ys.len());
}
/// Tests `FlatMap::fold` with items already picked off the front and back,
/// to make sure all parts of the `FlatMap` are folded correctly.
#[test]
fn test_iterator_flat_map_fold() {
let xs = [0, 3, 6];
let ys = [1, 2, 3, 4, 5, 6, 7];
let mut it = xs.iter().flat_map(|&x| x..x + 3);
assert_eq!(it.next(), Some(0));
assert_eq!(it.next_back(), Some(8));
let i = it.fold(0, |i, x| {
assert_eq!(x, ys[i]);
i + 1
});
assert_eq!(i, ys.len());
let mut it = xs.iter().flat_map(|&x| x..x + 3);
assert_eq!(it.next(), Some(0));
assert_eq!(it.next_back(), Some(8));
let i = it.rfold(ys.len(), |i, x| {
assert_eq!(x, ys[i - 1]);
i - 1
});
assert_eq!(i, 0);
}
#[test]
fn test_iterator_flatten() {
let xs = [0, 3, 6];
let ys = [0, 1, 2, 3, 4, 5, 6, 7, 8];
let it = xs.iter().map(|&x| (x..).step_by(1).take(3)).flatten();
let mut i = 0;
for x in it {
assert_eq!(x, ys[i]);
i += 1;
}
assert_eq!(i, ys.len());
}
/// Tests `Flatten::fold` with items already picked off the front and back,
/// to make sure all parts of the `Flatten` are folded correctly.
#[test]
fn test_iterator_flatten_fold() {
let xs = [0, 3, 6];
let ys = [1, 2, 3, 4, 5, 6, 7];
let mut it = xs.iter().map(|&x| x..x + 3).flatten();
assert_eq!(it.next(), Some(0));
assert_eq!(it.next_back(), Some(8));
let i = it.fold(0, |i, x| {
assert_eq!(x, ys[i]);
i + 1
});
assert_eq!(i, ys.len());
let mut it = xs.iter().map(|&x| x..x + 3).flatten();
assert_eq!(it.next(), Some(0));
assert_eq!(it.next_back(), Some(8));
let i = it.rfold(ys.len(), |i, x| {
assert_eq!(x, ys[i - 1]);
i - 1
});
assert_eq!(i, 0);
}
#[test]
fn test_inspect() {
let xs = [1, 2, 3, 4];
let mut n = 0;
let ys = xs.iter().cloned().inspect(|_| n += 1).collect::<Vec<usize>>();
assert_eq!(n, xs.len());
assert_eq!(&xs[..], &ys[..]);
}
#[test]
fn test_inspect_fold() {
let xs = [1, 2, 3, 4];
let mut n = 0;
{
let it = xs.iter().inspect(|_| n += 1);
let i = it.fold(0, |i, &x| {
assert_eq!(x, xs[i]);
i + 1
});
assert_eq!(i, xs.len());
}
assert_eq!(n, xs.len());
let mut n = 0;
{
let it = xs.iter().inspect(|_| n += 1);
let i = it.rfold(xs.len(), |i, &x| {
assert_eq!(x, xs[i - 1]);
i - 1
});
assert_eq!(i, 0);
}
assert_eq!(n, xs.len());
}
#[test]
fn test_cycle() {
let cycle_len = 3;
let it = (0..).step_by(1).take(cycle_len).cycle();
assert_eq!(it.size_hint(), (usize::MAX, None));
for (i, x) in it.take(100).enumerate() {
assert_eq!(i % cycle_len, x);
}
let mut it = (0..).step_by(1).take(0).cycle();
assert_eq!(it.size_hint(), (0, Some(0)));
assert_eq!(it.next(), None);
assert_eq!(empty::<i32>().cycle().fold(0, |acc, x| acc + x), 0);
assert_eq!(once(1).cycle().skip(1).take(4).fold(0, |acc, x| acc + x), 4);
assert_eq!((0..10).cycle().take(5).sum::<i32>(), 10);
assert_eq!((0..10).cycle().take(15).sum::<i32>(), 55);
assert_eq!((0..10).cycle().take(25).sum::<i32>(), 100);
let mut iter = (0..10).cycle();
iter.nth(14);
assert_eq!(iter.take(8).sum::<i32>(), 38);
let mut iter = (0..10).cycle();
iter.nth(9);
assert_eq!(iter.take(3).sum::<i32>(), 3);
}
#[test]
fn test_iterator_nth() {
let v: &[_] = &[0, 1, 2, 3, 4];
for i in 0..v.len() {
assert_eq!(v.iter().nth(i).unwrap(), &v[i]);
}
assert_eq!(v.iter().nth(v.len()), None);
}
#[test]
fn test_iterator_nth_back() {
let v: &[_] = &[0, 1, 2, 3, 4];
for i in 0..v.len() {
assert_eq!(v.iter().nth_back(i).unwrap(), &v[v.len() - 1 - i]);
}
assert_eq!(v.iter().nth_back(v.len()), None);
}
#[test]
fn test_iterator_rev_nth_back() {
let v: &[_] = &[0, 1, 2, 3, 4];
for i in 0..v.len() {
assert_eq!(v.iter().rev().nth_back(i).unwrap(), &v[i]);
}
assert_eq!(v.iter().rev().nth_back(v.len()), None);
}
#[test]
fn test_iterator_rev_nth() {
let v: &[_] = &[0, 1, 2, 3, 4];
for i in 0..v.len() {
assert_eq!(v.iter().rev().nth(i).unwrap(), &v[v.len() - 1 - i]);
}
assert_eq!(v.iter().rev().nth(v.len()), None);
}
#[test]
fn test_iterator_last() {
let v: &[_] = &[0, 1, 2, 3, 4];
assert_eq!(v.iter().last().unwrap(), &4);
assert_eq!(v[..1].iter().last().unwrap(), &0);
}
#[test]
fn test_iterator_len() {
let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(v[..4].iter().count(), 4);
assert_eq!(v[..10].iter().count(), 10);
assert_eq!(v[..0].iter().count(), 0);
}
#[test]
fn test_iterator_sum() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(v[..4].iter().cloned().sum::<i32>(), 6);
assert_eq!(v.iter().cloned().sum::<i32>(), 55);
assert_eq!(v[..0].iter().cloned().sum::<i32>(), 0);
}
#[test]
fn test_iterator_sum_result() {
let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Ok(10));
let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
assert_eq!(v.iter().cloned().sum::<Result<i32, _>>(), Err(()));
#[derive(PartialEq, Debug)]
struct S(Result<i32, ()>);
impl Sum<Result<i32, ()>> for S {
fn sum<I: Iterator<Item = Result<i32, ()>>>(mut iter: I) -> Self {
// takes the sum by repeatedly calling `next` on `iter`,
// thus testing that repeated calls to `ResultShunt::try_fold`
// produce the expected results
Self(iter.by_ref().sum())
}
}
let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
assert_eq!(v.iter().cloned().sum::<S>(), S(Ok(10)));
let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
assert_eq!(v.iter().cloned().sum::<S>(), S(Err(())));
}
#[test]
fn test_iterator_sum_option() {
let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
assert_eq!(v.iter().cloned().sum::<Option<i32>>(), Some(10));
let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
assert_eq!(v.iter().cloned().sum::<Option<i32>>(), None);
}
#[test]
fn test_iterator_product() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(v[..4].iter().cloned().product::<i32>(), 0);
assert_eq!(v[1..5].iter().cloned().product::<i32>(), 24);
assert_eq!(v[..0].iter().cloned().product::<i32>(), 1);
}
#[test]
fn test_iterator_product_result() {
let v: &[Result<i32, ()>] = &[Ok(1), Ok(2), Ok(3), Ok(4)];
assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Ok(24));
let v: &[Result<i32, ()>] = &[Ok(1), Err(()), Ok(3), Ok(4)];
assert_eq!(v.iter().cloned().product::<Result<i32, _>>(), Err(()));
}
/// A wrapper struct that implements `Eq` and `Ord` based on the wrapped
/// integer modulo 3. Used to test that `Iterator::max` and `Iterator::min`
/// return the correct element if some of them are equal.
#[derive(Debug)]
struct Mod3(i32);
impl PartialEq for Mod3 {
fn eq(&self, other: &Self) -> bool {
self.0 % 3 == other.0 % 3
}
}
impl Eq for Mod3 {}
impl PartialOrd for Mod3 {
fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
Some(self.cmp(other))
}
}
impl Ord for Mod3 {
fn cmp(&self, other: &Self) -> core::cmp::Ordering {
(self.0 % 3).cmp(&(other.0 % 3))
}
}
#[test]
fn test_iterator_product_option() {
let v: &[Option<i32>] = &[Some(1), Some(2), Some(3), Some(4)];
assert_eq!(v.iter().cloned().product::<Option<i32>>(), Some(24));
let v: &[Option<i32>] = &[Some(1), None, Some(3), Some(4)];
assert_eq!(v.iter().cloned().product::<Option<i32>>(), None);
}
#[test]
fn test_iterator_max() {
let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(v[..4].iter().cloned().max(), Some(3));
assert_eq!(v.iter().cloned().max(), Some(10));
assert_eq!(v[..0].iter().cloned().max(), None);
assert_eq!(v.iter().cloned().map(Mod3).max().map(|x| x.0), Some(8));
}
#[test]
fn test_iterator_min() {
let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
assert_eq!(v[..4].iter().cloned().min(), Some(0));
assert_eq!(v.iter().cloned().min(), Some(0));
assert_eq!(v[..0].iter().cloned().min(), None);
assert_eq!(v.iter().cloned().map(Mod3).min().map(|x| x.0), Some(0));
}
#[test]
fn test_iterator_size_hint() {
let c = (0..).step_by(1);
let v: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
let v2 = &[10, 11, 12];
let vi = v.iter();
assert_eq!((0..).size_hint(), (usize::MAX, None));
assert_eq!(c.size_hint(), (usize::MAX, None));
assert_eq!(vi.clone().size_hint(), (10, Some(10)));
assert_eq!(c.clone().take(5).size_hint(), (5, Some(5)));
assert_eq!(c.clone().skip(5).size_hint().1, None);
assert_eq!(c.clone().take_while(|_| false).size_hint(), (0, None));
assert_eq!(c.clone().map_while(|_| None::<()>).size_hint(), (0, None));
assert_eq!(c.clone().skip_while(|_| false).size_hint(), (0, None));
assert_eq!(c.clone().enumerate().size_hint(), (usize::MAX, None));
assert_eq!(c.clone().chain(vi.clone().cloned()).size_hint(), (usize::MAX, None));
assert_eq!(c.clone().zip(vi.clone()).size_hint(), (10, Some(10)));
assert_eq!(c.clone().scan(0, |_, _| Some(0)).size_hint(), (0, None));
assert_eq!(c.clone().filter(|_| false).size_hint(), (0, None));
assert_eq!(c.clone().map(|_| 0).size_hint(), (usize::MAX, None));
assert_eq!(c.filter_map(|_| Some(0)).size_hint(), (0, None));
assert_eq!(vi.clone().take(5).size_hint(), (5, Some(5)));
assert_eq!(vi.clone().take(12).size_hint(), (10, Some(10)));
assert_eq!(vi.clone().skip(3).size_hint(), (7, Some(7)));
assert_eq!(vi.clone().skip(12).size_hint(), (0, Some(0)));
assert_eq!(vi.clone().take_while(|_| false).size_hint(), (0, Some(10)));
assert_eq!(vi.clone().map_while(|_| None::<()>).size_hint(), (0, Some(10)));
assert_eq!(vi.clone().skip_while(|_| false).size_hint(), (0, Some(10)));
assert_eq!(vi.clone().enumerate().size_hint(), (10, Some(10)));
assert_eq!(vi.clone().chain(v2).size_hint(), (13, Some(13)));
assert_eq!(vi.clone().zip(v2).size_hint(), (3, Some(3)));
assert_eq!(vi.clone().scan(0, |_, _| Some(0)).size_hint(), (0, Some(10)));
assert_eq!(vi.clone().filter(|_| false).size_hint(), (0, Some(10)));
assert_eq!(vi.clone().map(|&i| i + 1).size_hint(), (10, Some(10)));
assert_eq!(vi.filter_map(|_| Some(0)).size_hint(), (0, Some(10)));
}
#[test]
fn test_collect() {
let a = vec![1, 2, 3, 4, 5];
let b: Vec<isize> = a.iter().cloned().collect();
assert!(a == b);
}
#[test]
fn test_all() {
let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
assert!(v.iter().all(|&x| x < 10));
assert!(!v.iter().all(|&x| x % 2 == 0));
assert!(!v.iter().all(|&x| x > 100));
assert!(v[..0].iter().all(|_| panic!()));
}
#[test]
fn test_any() {
let v: Box<[isize]> = Box::new([1, 2, 3, 4, 5]);
assert!(v.iter().any(|&x| x < 10));
assert!(v.iter().any(|&x| x % 2 == 0));
assert!(!v.iter().any(|&x| x > 100));
assert!(!v[..0].iter().any(|_| panic!()));
}
#[test]
fn test_find() {
let v: &[isize] = &[1, 3, 9, 27, 103, 14, 11];
assert_eq!(*v.iter().find(|&&x| x & 1 == 0).unwrap(), 14);
assert_eq!(*v.iter().find(|&&x| x % 3 == 0).unwrap(), 3);
assert!(v.iter().find(|&&x| x % 12 == 0).is_none());
}
#[test]
fn test_find_map() {
let xs: &[isize] = &[];
assert_eq!(xs.iter().find_map(half_if_even), None);
let xs: &[isize] = &[3, 5];
assert_eq!(xs.iter().find_map(half_if_even), None);
let xs: &[isize] = &[4, 5];
assert_eq!(xs.iter().find_map(half_if_even), Some(2));
let xs: &[isize] = &[3, 6];
assert_eq!(xs.iter().find_map(half_if_even), Some(3));
let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
let mut iter = xs.iter();
assert_eq!(iter.find_map(half_if_even), Some(1));
assert_eq!(iter.find_map(half_if_even), Some(2));
assert_eq!(iter.find_map(half_if_even), Some(3));
assert_eq!(iter.next(), Some(&7));
fn half_if_even(x: &isize) -> Option<isize> {
if x % 2 == 0 { Some(x / 2) } else { None }
}
}
#[test]
fn test_try_find() {
let xs: &[isize] = &[];
assert_eq!(xs.iter().try_find(testfn), Ok(None));
let xs: &[isize] = &[1, 2, 3, 4];
assert_eq!(xs.iter().try_find(testfn), Ok(Some(&2)));
let xs: &[isize] = &[1, 3, 4];
assert_eq!(xs.iter().try_find(testfn), Err(()));
let xs: &[isize] = &[1, 2, 3, 4, 5, 6, 7];
let mut iter = xs.iter();
assert_eq!(iter.try_find(testfn), Ok(Some(&2)));
assert_eq!(iter.try_find(testfn), Err(()));
assert_eq!(iter.next(), Some(&5));
fn testfn(x: &&isize) -> Result<bool, ()> {
if **x == 2 {
return Ok(true);
}
if **x == 4 {
return Err(());
}
Ok(false)
}
}
#[test]
fn test_try_find_api_usability() -> Result<(), Box<dyn std::error::Error>> {
let a = ["1", "2"];
let is_my_num = |s: &str, search: i32| -> Result<bool, std::num::ParseIntError> {
Ok(s.parse::<i32>()? == search)
};
let val = a.iter().try_find(|&&s| is_my_num(s, 2))?;
assert_eq!(val, Some(&"2"));
Ok(())
}
#[test]
fn test_position() {
let v = &[1, 3, 9, 27, 103, 14, 11];
assert_eq!(v.iter().position(|x| *x & 1 == 0).unwrap(), 5);
assert_eq!(v.iter().position(|x| *x % 3 == 0).unwrap(), 1);
assert!(v.iter().position(|x| *x % 12 == 0).is_none());
}
#[test]
fn test_count() {
let xs = &[1, 2, 2, 1, 5, 9, 0, 2];
assert_eq!(xs.iter().filter(|x| **x == 2).count(), 3);
assert_eq!(xs.iter().filter(|x| **x == 5).count(), 1);
assert_eq!(xs.iter().filter(|x| **x == 95).count(), 0);
}
#[test]
fn test_max_by_key() {
let xs: &[isize] = &[-3, 0, 1, 5, -10];
assert_eq!(*xs.iter().max_by_key(|x| x.abs()).unwrap(), -10);
}
#[test]
fn test_max_by() {
let xs: &[isize] = &[-3, 0, 1, 5, -10];
assert_eq!(*xs.iter().max_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), -10);
}
#[test]
fn test_min_by_key() {
let xs: &[isize] = &[-3, 0, 1, 5, -10];
assert_eq!(*xs.iter().min_by_key(|x| x.abs()).unwrap(), 0);
}
#[test]
fn test_min_by() {
let xs: &[isize] = &[-3, 0, 1, 5, -10];
assert_eq!(*xs.iter().min_by(|x, y| x.abs().cmp(&y.abs())).unwrap(), 0);
}
#[test]
fn test_by_ref() {
let mut xs = 0..10;
// sum the first five values
let partial_sum = xs.by_ref().take(5).fold(0, |a, b| a + b);
assert_eq!(partial_sum, 10);
assert_eq!(xs.next(), Some(5));
}
#[test]
fn test_rev() {
let xs = [2, 4, 6, 8, 10, 12, 14, 16];
let mut it = xs.iter();
it.next();
it.next();
assert!(it.rev().cloned().collect::<Vec<isize>>() == vec![16, 14, 12, 10, 8, 6]);
}
#[test]
fn test_copied() {
let xs = [2, 4, 6, 8];
let mut it = xs.iter().copied();
assert_eq!(it.len(), 4);
assert_eq!(it.next(), Some(2));
assert_eq!(it.len(), 3);
assert_eq!(it.next(), Some(4));
assert_eq!(it.len(), 2);
assert_eq!(it.next_back(), Some(8));
assert_eq!(it.len(), 1);
assert_eq!(it.next_back(), Some(6));
assert_eq!(it.len(), 0);
assert_eq!(it.next_back(), None);
}
#[test]
fn test_cloned() {
let xs = [2, 4, 6, 8];
let mut it = xs.iter().cloned();
assert_eq!(it.len(), 4);
assert_eq!(it.next(), Some(2));
assert_eq!(it.len(), 3);
assert_eq!(it.next(), Some(4));
assert_eq!(it.len(), 2);
assert_eq!(it.next_back(), Some(8));
assert_eq!(it.len(), 1);
assert_eq!(it.next_back(), Some(6));
assert_eq!(it.len(), 0);
assert_eq!(it.next_back(), None);
}
#[test]
fn test_cloned_side_effects() {
let mut count = 0;
{
let iter = [1, 2, 3]
.iter()
.map(|x| {
count += 1;
x
})
.cloned()
.zip(&[1]);
for _ in iter {}
}
assert_eq!(count, 2);
}
#[test]
fn test_double_ended_map() {
let xs = [1, 2, 3, 4, 5, 6];
let mut it = xs.iter().map(|&x| x * -1);
assert_eq!(it.next(), Some(-1));
assert_eq!(it.next(), Some(-2));
assert_eq!(it.next_back(), Some(-6));
assert_eq!(it.next_back(), Some(-5));
assert_eq!(it.next(), Some(-3));
assert_eq!(it.next_back(), Some(-4));
assert_eq!(it.next(), None);
}
#[test]
fn test_double_ended_enumerate() {
let xs = [1, 2, 3, 4, 5, 6];
let mut it = xs.iter().cloned().enumerate();
assert_eq!(it.next(), Some((0, 1)));
assert_eq!(it.next(), Some((1, 2)));
assert_eq!(it.next_back(), Some((5, 6)));
assert_eq!(it.next_back(), Some((4, 5)));
assert_eq!(it.next_back(), Some((3, 4)));
assert_eq!(it.next_back(), Some((2, 3)));
assert_eq!(it.next(), None);
}
#[test]
fn test_double_ended_zip() {
let xs = [1, 2, 3, 4, 5, 6];
let ys = [1, 2, 3, 7];
let a = xs.iter().cloned();
let b = ys.iter().cloned();
let mut it = a.zip(b);
assert_eq!(it.next(), Some((1, 1)));
assert_eq!(it.next(), Some((2, 2)));
assert_eq!(it.next_back(), Some((4, 7)));
assert_eq!(it.next_back(), Some((3, 3)));
assert_eq!(it.next(), None);
}
#[test]
fn test_double_ended_filter() {
let xs = [1, 2, 3, 4, 5, 6];
let mut it = xs.iter().filter(|&x| *x & 1 == 0);
assert_eq!(it.next_back().unwrap(), &6);
assert_eq!(it.next_back().unwrap(), &4);
assert_eq!(it.next().unwrap(), &2);
assert_eq!(it.next_back(), None);
}
#[test]
fn test_double_ended_filter_map() {
let xs = [1, 2, 3, 4, 5, 6];
let mut it = xs.iter().filter_map(|&x| if x & 1 == 0 { Some(x * 2) } else { None });
assert_eq!(it.next_back().unwrap(), 12);
assert_eq!(it.next_back().unwrap(), 8);
assert_eq!(it.next().unwrap(), 4);
assert_eq!(it.next_back(), None);
}
#[test]
fn test_double_ended_chain() {
let xs = [1, 2, 3, 4, 5];
let ys = [7, 9, 11];
let mut it = xs.iter().chain(&ys).rev();
assert_eq!(it.next().unwrap(), &11);
assert_eq!(it.next().unwrap(), &9);
assert_eq!(it.next_back().unwrap(), &1);
assert_eq!(it.next_back().unwrap(), &2);
assert_eq!(it.next_back().unwrap(), &3);
assert_eq!(it.next_back().unwrap(), &4);
assert_eq!(it.next_back().unwrap(), &5);
assert_eq!(it.next_back().unwrap(), &7);
assert_eq!(it.next_back(), None);
// test that .chain() is well behaved with an unfused iterator
struct CrazyIterator(bool);
impl CrazyIterator {
fn new() -> CrazyIterator {
CrazyIterator(false)
}
}
impl Iterator for CrazyIterator {
type Item = i32;
fn next(&mut self) -> Option<i32> {
if self.0 {
Some(99)
} else {
self.0 = true;
None
}
}
}
impl DoubleEndedIterator for CrazyIterator {
fn next_back(&mut self) -> Option<i32> {
self.next()
}
}
assert_eq!(CrazyIterator::new().chain(0..10).rev().last(), Some(0));
assert!((0..10).chain(CrazyIterator::new()).rev().any(|i| i == 0));
}
#[test]
fn test_rposition() {
fn f(xy: &(isize, char)) -> bool {
let (_x, y) = *xy;
y == 'b'
}
fn g(xy: &(isize, char)) -> bool {
let (_x, y) = *xy;
y == 'd'
}
let v = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'b')];
assert_eq!(v.iter().rposition(f), Some(3));
assert!(v.iter().rposition(g).is_none());
}
#[test]
fn test_rev_rposition() {
let v = [0, 0, 1, 1];
assert_eq!(v.iter().rev().rposition(|&x| x == 1), Some(1));
}
#[test]
#[should_panic]
fn test_rposition_panic() {
let v: [(Box<_>, Box<_>); 4] = [(box 0, box 0), (box 0, box 0), (box 0, box 0), (box 0, box 0)];
let mut i = 0;
v.iter().rposition(|_elt| {
if i == 2 {
panic!()
}
i += 1;
false
});
}
#[test]
fn test_double_ended_flat_map() {
let u = [0, 1];
let v = [5, 6, 7, 8];
let mut it = u.iter().flat_map(|x| &v[*x..v.len()]);
assert_eq!(it.next_back().unwrap(), &8);
assert_eq!(it.next().unwrap(), &5);
assert_eq!(it.next_back().unwrap(), &7);
assert_eq!(it.next_back().unwrap(), &6);
assert_eq!(it.next_back().unwrap(), &8);
assert_eq!(it.next().unwrap(), &6);
assert_eq!(it.next_back().unwrap(), &7);
assert_eq!(it.next_back(), None);
assert_eq!(it.next(), None);
assert_eq!(it.next_back(), None);
}
#[test]
fn test_double_ended_flatten() {
let u = [0, 1];
let v = [5, 6, 7, 8];
let mut it = u.iter().map(|x| &v[*x..v.len()]).flatten();
assert_eq!(it.next_back().unwrap(), &8);
assert_eq!(it.next().unwrap(), &5);
assert_eq!(it.next_back().unwrap(), &7);
assert_eq!(it.next_back().unwrap(), &6);
assert_eq!(it.next_back().unwrap(), &8);
assert_eq!(it.next().unwrap(), &6);
assert_eq!(it.next_back().unwrap(), &7);
assert_eq!(it.next_back(), None);
assert_eq!(it.next(), None);
assert_eq!(it.next_back(), None);
}
#[test]
fn test_double_ended_range() {
assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
for _ in (10..0).rev() {
panic!("unreachable");
}
assert_eq!((11..14).rev().collect::<Vec<_>>(), [13, 12, 11]);
for _ in (10..0).rev() {
panic!("unreachable");
}
}
#[test]
fn test_range() {
assert_eq!((0..5).collect::<Vec<_>>(), [0, 1, 2, 3, 4]);
assert_eq!((-10..-1).collect::<Vec<_>>(), [-10, -9, -8, -7, -6, -5, -4, -3, -2]);
assert_eq!((0..5).rev().collect::<Vec<_>>(), [4, 3, 2, 1, 0]);
assert_eq!((200..-5).count(), 0);
assert_eq!((200..-5).rev().count(), 0);
assert_eq!((200..200).count(), 0);
assert_eq!((200..200).rev().count(), 0);
assert_eq!((0..100).size_hint(), (100, Some(100)));
// this test is only meaningful when sizeof usize < sizeof u64
assert_eq!((usize::MAX - 1..usize::MAX).size_hint(), (1, Some(1)));
assert_eq!((-10..-1).size_hint(), (9, Some(9)));
assert_eq!((-1..-10).size_hint(), (0, Some(0)));
assert_eq!((-70..58).size_hint(), (128, Some(128)));
assert_eq!((-128..127).size_hint(), (255, Some(255)));
assert_eq!(
(-2..isize::MAX).size_hint(),
(isize::MAX as usize + 2, Some(isize::MAX as usize + 2))
);
}
#[test]
fn test_range_exhaustion() {
let mut r = 10..10;
assert!(r.is_empty());
assert_eq!(r.next(), None);
assert_eq!(r.next_back(), None);
assert_eq!(r, 10..10);
let mut r = 10..12;
assert_eq!(r.next(), Some(10));
assert_eq!(r.next(), Some(11));
assert!(r.is_empty());
assert_eq!(r, 12..12);
assert_eq!(r.next(), None);
let mut r = 10..12;
assert_eq!(r.next_back(), Some(11));
assert_eq!(r.next_back(), Some(10));
assert!(r.is_empty());
assert_eq!(r, 10..10);
assert_eq!(r.next_back(), None);
let mut r = 100..10;
assert!(r.is_empty());
assert_eq!(r.next(), None);
assert_eq!(r.next_back(), None);
assert_eq!(r, 100..10);
}
#[test]
fn test_range_inclusive_exhaustion() {
let mut r = 10..=10;
assert_eq!(r.next(), Some(10));
assert!(r.is_empty());
assert_eq!(r.next(), None);
assert_eq!(r.next(), None);
let mut r = 10..=10;
assert_eq!(r.next_back(), Some(10));
assert!(r.is_empty());
assert_eq!(r.next_back(), None);
let mut r = 10..=12;
assert_eq!(r.next(), Some(10));
assert_eq!(r.next(), Some(11));
assert_eq!(r.next(), Some(12));
assert!(r.is_empty());
assert_eq!(r.next(), None);
let mut r = 10..=12;
assert_eq!(r.next_back(), Some(12));
assert_eq!(r.next_back(), Some(11));
assert_eq!(r.next_back(), Some(10));
assert!(r.is_empty());
assert_eq!(r.next_back(), None);
let mut r = 10..=12;
assert_eq!(r.nth(2), Some(12));
assert!(r.is_empty());
assert_eq!(r.next(), None);
let mut r = 10..=12;
assert_eq!(r.nth(5), None);
assert!(r.is_empty());
assert_eq!(r.next(), None);
let mut r = 100..=10;
assert_eq!(r.next(), None);
assert!(r.is_empty());
assert_eq!(r.next(), None);
assert_eq!(r.next(), None);
assert_eq!(r, 100..=10);
let mut r = 100..=10;
assert_eq!(r.next_back(), None);
assert!(r.is_empty());
assert_eq!(r.next_back(), None);
assert_eq!(r.next_back(), None);
assert_eq!(r, 100..=10);
}
#[test]
fn test_range_nth() {
assert_eq!((10..15).nth(0), Some(10));
assert_eq!((10..15).nth(1), Some(11));
assert_eq!((10..15).nth(4), Some(14));
assert_eq!((10..15).nth(5), None);
let mut r = 10..20;
assert_eq!(r.nth(2), Some(12));
assert_eq!(r, 13..20);
assert_eq!(r.nth(2), Some(15));
assert_eq!(r, 16..20);
assert_eq!(r.nth(10), None);
assert_eq!(r, 20..20);
}
#[test]
fn test_range_nth_back() {
assert_eq!((10..15).nth_back(0), Some(14));
assert_eq!((10..15).nth_back(1), Some(13));
assert_eq!((10..15).nth_back(4), Some(10));
assert_eq!((10..15).nth_back(5), None);
assert_eq!((-120..80_i8).nth_back(199), Some(-120));
let mut r = 10..20;
assert_eq!(r.nth_back(2), Some(17));
assert_eq!(r, 10..17);
assert_eq!(r.nth_back(2), Some(14));
assert_eq!(r, 10..14);
assert_eq!(r.nth_back(10), None);
assert_eq!(r, 10..10);
}
#[test]
fn test_range_from_nth() {
assert_eq!((10..).nth(0), Some(10));
assert_eq!((10..).nth(1), Some(11));
assert_eq!((10..).nth(4), Some(14));
let mut r = 10..;
assert_eq!(r.nth(2), Some(12));
assert_eq!(r, 13..);
assert_eq!(r.nth(2), Some(15));
assert_eq!(r, 16..);
assert_eq!(r.nth(10), Some(26));
assert_eq!(r, 27..);
assert_eq!((0..).size_hint(), (usize::MAX, None));
}
fn is_trusted_len<I: TrustedLen>(_: I) {}
#[test]
fn test_range_from_take() {
let mut it = (0..).take(3);
assert_eq!(it.next(), Some(0));
assert_eq!(it.next(), Some(1));
assert_eq!(it.next(), Some(2));
assert_eq!(it.next(), None);
is_trusted_len((0..).take(3));
assert_eq!((0..).take(3).size_hint(), (3, Some(3)));
assert_eq!((0..).take(0).size_hint(), (0, Some(0)));
assert_eq!((0..).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
}
#[test]
fn test_range_from_take_collect() {
let v: Vec<_> = (0..).take(3).collect();
assert_eq!(v, vec![0, 1, 2]);
}
#[test]
fn test_range_inclusive_nth() {
assert_eq!((10..=15).nth(0), Some(10));
assert_eq!((10..=15).nth(1), Some(11));
assert_eq!((10..=15).nth(5), Some(15));
assert_eq!((10..=15).nth(6), None);
let mut r = 10_u8..=20;
assert_eq!(r.nth(2), Some(12));
assert_eq!(r, 13..=20);
assert_eq!(r.nth(2), Some(15));
assert_eq!(r, 16..=20);
assert_eq!(r.is_empty(), false);
assert_eq!(ExactSizeIterator::is_empty(&r), false);
assert_eq!(r.nth(10), None);
assert_eq!(r.is_empty(), true);
assert_eq!(ExactSizeIterator::is_empty(&r), true);
}
#[test]
fn test_range_inclusive_nth_back() {
assert_eq!((10..=15).nth_back(0), Some(15));
assert_eq!((10..=15).nth_back(1), Some(14));
assert_eq!((10..=15).nth_back(5), Some(10));
assert_eq!((10..=15).nth_back(6), None);
assert_eq!((-120..=80_i8).nth_back(200), Some(-120));
let mut r = 10_u8..=20;
assert_eq!(r.nth_back(2), Some(18));
assert_eq!(r, 10..=17);
assert_eq!(r.nth_back(2), Some(15));
assert_eq!(r, 10..=14);
assert_eq!(r.is_empty(), false);
assert_eq!(ExactSizeIterator::is_empty(&r), false);
assert_eq!(r.nth_back(10), None);
assert_eq!(r.is_empty(), true);
assert_eq!(ExactSizeIterator::is_empty(&r), true);
}
#[test]
fn test_range_step() {
#![allow(deprecated)]
assert_eq!((0..20).step_by(5).collect::<Vec<isize>>(), [0, 5, 10, 15]);
assert_eq!((1..21).rev().step_by(5).collect::<Vec<isize>>(), [20, 15, 10, 5]);
assert_eq!((1..21).rev().step_by(6).collect::<Vec<isize>>(), [20, 14, 8, 2]);
assert_eq!((200..255).step_by(50).collect::<Vec<u8>>(), [200, 250]);
assert_eq!((200..-5).step_by(1).collect::<Vec<isize>>(), []);
assert_eq!((200..200).step_by(1).collect::<Vec<isize>>(), []);
assert_eq!((0..20).step_by(1).size_hint(), (20, Some(20)));
assert_eq!((0..20).step_by(21).size_hint(), (1, Some(1)));
assert_eq!((0..20).step_by(5).size_hint(), (4, Some(4)));
assert_eq!((1..21).rev().step_by(5).size_hint(), (4, Some(4)));
assert_eq!((1..21).rev().step_by(6).size_hint(), (4, Some(4)));
assert_eq!((20..-5).step_by(1).size_hint(), (0, Some(0)));
assert_eq!((20..20).step_by(1).size_hint(), (0, Some(0)));
assert_eq!((i8::MIN..i8::MAX).step_by(-(i8::MIN as i32) as usize).size_hint(), (2, Some(2)));
assert_eq!((i16::MIN..i16::MAX).step_by(i16::MAX as usize).size_hint(), (3, Some(3)));
assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
}
#[test]
fn test_step_by_skip() {
assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
assert_eq!((0..=50).step_by(10).nth(3), Some(30));
assert_eq!((200..=255u8).step_by(10).nth(3), Some(230));
}
#[test]
fn test_range_inclusive_step() {
assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
assert_eq!((0..=5).step_by(1).collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5]);
assert_eq!((200..=255u8).step_by(10).collect::<Vec<_>>(), [200, 210, 220, 230, 240, 250]);
assert_eq!((250..=255u8).step_by(1).collect::<Vec<_>>(), [250, 251, 252, 253, 254, 255]);
}
#[test]
fn test_range_last_max() {
assert_eq!((0..20).last(), Some(19));
assert_eq!((-20..0).last(), Some(-1));
assert_eq!((5..5).last(), None);
assert_eq!((0..20).max(), Some(19));
assert_eq!((-20..0).max(), Some(-1));
assert_eq!((5..5).max(), None);
}
#[test]
fn test_range_inclusive_last_max() {
assert_eq!((0..=20).last(), Some(20));
assert_eq!((-20..=0).last(), Some(0));
assert_eq!((5..=5).last(), Some(5));
let mut r = 10..=10;
r.next();
assert_eq!(r.last(), None);
assert_eq!((0..=20).max(), Some(20));
assert_eq!((-20..=0).max(), Some(0));
assert_eq!((5..=5).max(), Some(5));
let mut r = 10..=10;
r.next();
assert_eq!(r.max(), None);
}
#[test]
fn test_range_min() {
assert_eq!((0..20).min(), Some(0));
assert_eq!((-20..0).min(), Some(-20));
assert_eq!((5..5).min(), None);
}
#[test]
fn test_range_inclusive_min() {
assert_eq!((0..=20).min(), Some(0));
assert_eq!((-20..=0).min(), Some(-20));
assert_eq!((5..=5).min(), Some(5));
let mut r = 10..=10;
r.next();
assert_eq!(r.min(), None);
}
#[test]
fn test_range_inclusive_folds() {
assert_eq!((1..=10).sum::<i32>(), 55);
assert_eq!((1..=10).rev().sum::<i32>(), 55);
let mut it = 44..=50;
assert_eq!(it.try_fold(0, i8::checked_add), None);
assert_eq!(it, 47..=50);
assert_eq!(it.try_fold(0, i8::checked_add), None);
assert_eq!(it, 50..=50);
assert_eq!(it.try_fold(0, i8::checked_add), Some(50));
assert!(it.is_empty());
assert_eq!(it.try_fold(0, i8::checked_add), Some(0));
assert!(it.is_empty());
let mut it = 40..=47;
assert_eq!(it.try_rfold(0, i8::checked_add), None);
assert_eq!(it, 40..=44);
assert_eq!(it.try_rfold(0, i8::checked_add), None);
assert_eq!(it, 40..=41);
assert_eq!(it.try_rfold(0, i8::checked_add), Some(81));
assert!(it.is_empty());
assert_eq!(it.try_rfold(0, i8::checked_add), Some(0));
assert!(it.is_empty());
let mut it = 10..=20;
assert_eq!(it.try_fold(0, |a, b| Some(a + b)), Some(165));
assert!(it.is_empty());
assert_eq!(it.try_fold(0, |a, b| Some(a + b)), Some(0));
assert!(it.is_empty());
let mut it = 10..=20;
assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(165));
assert!(it.is_empty());
assert_eq!(it.try_rfold(0, |a, b| Some(a + b)), Some(0));
assert!(it.is_empty());
}
#[test]
fn test_range_size_hint() {
use core::usize::MAX as UMAX;
assert_eq!((0..0usize).size_hint(), (0, Some(0)));
assert_eq!((0..100usize).size_hint(), (100, Some(100)));
assert_eq!((0..UMAX).size_hint(), (UMAX, Some(UMAX)));
let umax = u128::try_from(UMAX).unwrap();
assert_eq!((0..0u128).size_hint(), (0, Some(0)));
assert_eq!((0..100u128).size_hint(), (100, Some(100)));
assert_eq!((0..umax).size_hint(), (UMAX, Some(UMAX)));
assert_eq!((0..umax + 1).size_hint(), (UMAX, None));
use core::isize::{MAX as IMAX, MIN as IMIN};
assert_eq!((0..0isize).size_hint(), (0, Some(0)));
assert_eq!((-100..100isize).size_hint(), (200, Some(200)));
assert_eq!((IMIN..IMAX).size_hint(), (UMAX, Some(UMAX)));
let imin = i128::try_from(IMIN).unwrap();
let imax = i128::try_from(IMAX).unwrap();
assert_eq!((0..0i128).size_hint(), (0, Some(0)));
assert_eq!((-100..100i128).size_hint(), (200, Some(200)));
assert_eq!((imin..imax).size_hint(), (UMAX, Some(UMAX)));
assert_eq!((imin..imax + 1).size_hint(), (UMAX, None));
}
#[test]
fn test_range_inclusive_size_hint() {
use core::usize::MAX as UMAX;
assert_eq!((1..=0usize).size_hint(), (0, Some(0)));
assert_eq!((0..=0usize).size_hint(), (1, Some(1)));
assert_eq!((0..=100usize).size_hint(), (101, Some(101)));
assert_eq!((0..=UMAX - 1).size_hint(), (UMAX, Some(UMAX)));
assert_eq!((0..=UMAX).size_hint(), (UMAX, None));
let umax = u128::try_from(UMAX).unwrap();
assert_eq!((1..=0u128).size_hint(), (0, Some(0)));
assert_eq!((0..=0u128).size_hint(), (1, Some(1)));
assert_eq!((0..=100u128).size_hint(), (101, Some(101)));
assert_eq!((0..=umax - 1).size_hint(), (UMAX, Some(UMAX)));
assert_eq!((0..=umax).size_hint(), (UMAX, None));
assert_eq!((0..=umax + 1).size_hint(), (UMAX, None));
use core::isize::{MAX as IMAX, MIN as IMIN};
assert_eq!((0..=-1isize).size_hint(), (0, Some(0)));
assert_eq!((0..=0isize).size_hint(), (1, Some(1)));
assert_eq!((-100..=100isize).size_hint(), (201, Some(201)));
assert_eq!((IMIN..=IMAX - 1).size_hint(), (UMAX, Some(UMAX)));
assert_eq!((IMIN..=IMAX).size_hint(), (UMAX, None));
let imin = i128::try_from(IMIN).unwrap();
let imax = i128::try_from(IMAX).unwrap();
assert_eq!((0..=-1i128).size_hint(), (0, Some(0)));
assert_eq!((0..=0i128).size_hint(), (1, Some(1)));
assert_eq!((-100..=100i128).size_hint(), (201, Some(201)));
assert_eq!((imin..=imax - 1).size_hint(), (UMAX, Some(UMAX)));
assert_eq!((imin..=imax).size_hint(), (UMAX, None));
assert_eq!((imin..=imax + 1).size_hint(), (UMAX, None));
}
#[test]
fn test_repeat() {
let mut it = repeat(42);
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), Some(42));
assert_eq!(repeat(42).size_hint(), (usize::MAX, None));
}
#[test]
fn test_repeat_take() {
let mut it = repeat(42).take(3);
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), None);
is_trusted_len(repeat(42).take(3));
assert_eq!(repeat(42).take(3).size_hint(), (3, Some(3)));
assert_eq!(repeat(42).take(0).size_hint(), (0, Some(0)));
assert_eq!(repeat(42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
}
#[test]
fn test_repeat_take_collect() {
let v: Vec<_> = repeat(42).take(3).collect();
assert_eq!(v, vec![42, 42, 42]);
}
#[test]
fn test_repeat_with() {
#[derive(PartialEq, Debug)]
struct NotClone(usize);
let mut it = repeat_with(|| NotClone(42));
assert_eq!(it.next(), Some(NotClone(42)));
assert_eq!(it.next(), Some(NotClone(42)));
assert_eq!(it.next(), Some(NotClone(42)));
assert_eq!(repeat_with(|| NotClone(42)).size_hint(), (usize::MAX, None));
}
#[test]
fn test_repeat_with_take() {
let mut it = repeat_with(|| 42).take(3);
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), None);
is_trusted_len(repeat_with(|| 42).take(3));
assert_eq!(repeat_with(|| 42).take(3).size_hint(), (3, Some(3)));
assert_eq!(repeat_with(|| 42).take(0).size_hint(), (0, Some(0)));
assert_eq!(repeat_with(|| 42).take(usize::MAX).size_hint(), (usize::MAX, Some(usize::MAX)));
}
#[test]
fn test_repeat_with_take_collect() {
let mut curr = 1;
let v: Vec<_> = repeat_with(|| {
let tmp = curr;
curr *= 2;
tmp
})
.take(5)
.collect();
assert_eq!(v, vec![1, 2, 4, 8, 16]);
}
#[test]
fn test_successors() {
let mut powers_of_10 = successors(Some(1_u16), |n| n.checked_mul(10));
assert_eq!(powers_of_10.by_ref().collect::<Vec<_>>(), &[1, 10, 100, 1_000, 10_000]);
assert_eq!(powers_of_10.next(), None);
let mut empty = successors(None::<u32>, |_| unimplemented!());
assert_eq!(empty.next(), None);
assert_eq!(empty.next(), None);
}
#[test]
fn test_fuse() {
let mut it = 0..3;
assert_eq!(it.len(), 3);
assert_eq!(it.next(), Some(0));
assert_eq!(it.len(), 2);
assert_eq!(it.next(), Some(1));
assert_eq!(it.len(), 1);
assert_eq!(it.next(), Some(2));
assert_eq!(it.len(), 0);
assert_eq!(it.next(), None);
assert_eq!(it.len(), 0);
assert_eq!(it.next(), None);
assert_eq!(it.len(), 0);
assert_eq!(it.next(), None);
assert_eq!(it.len(), 0);
}
#[test]
fn test_fuse_nth() {
let xs = [0, 1, 2];
let mut it = xs.iter();
assert_eq!(it.len(), 3);
assert_eq!(it.nth(2), Some(&2));
assert_eq!(it.len(), 0);
assert_eq!(it.nth(2), None);
assert_eq!(it.len(), 0);
}
#[test]
fn test_fuse_last() {
let xs = [0, 1, 2];
let it = xs.iter();
assert_eq!(it.len(), 3);
assert_eq!(it.last(), Some(&2));
}
#[test]
fn test_fuse_count() {
let xs = [0, 1, 2];
let it = xs.iter();
assert_eq!(it.len(), 3);
assert_eq!(it.count(), 3);
// Can't check len now because count consumes.
}
#[test]
fn test_fuse_fold() {
let xs = [0, 1, 2];
let it = xs.iter(); // `FusedIterator`
let i = it.fuse().fold(0, |i, &x| {
assert_eq!(x, xs[i]);
i + 1
});
assert_eq!(i, xs.len());
let it = xs.iter(); // `FusedIterator`
let i = it.fuse().rfold(xs.len(), |i, &x| {
assert_eq!(x, xs[i - 1]);
i - 1
});
assert_eq!(i, 0);
let it = xs.iter().scan((), |_, &x| Some(x)); // `!FusedIterator`
let i = it.fuse().fold(0, |i, x| {
assert_eq!(x, xs[i]);
i + 1
});
assert_eq!(i, xs.len());
}
#[test]
fn test_once() {
let mut it = once(42);
assert_eq!(it.next(), Some(42));
assert_eq!(it.next(), None);
}
#[test]
fn test_once_with() {
let count = Cell::new(0);
let mut it = once_with(|| {
count.set(count.get() + 1);
42
});
assert_eq!(count.get(), 0);
assert_eq!(it.next(), Some(42));
assert_eq!(count.get(), 1);
assert_eq!(it.next(), None);
assert_eq!(count.get(), 1);
assert_eq!(it.next(), None);
assert_eq!(count.get(), 1);
}
#[test]
fn test_empty() {
let mut it = empty::<i32>();
assert_eq!(it.next(), None);
}
#[test]
fn test_chain_fold() {
let xs = [1, 2, 3];
let ys = [1, 2, 0];
let mut iter = xs.iter().chain(&ys);
iter.next();
let mut result = Vec::new();
iter.fold((), |(), &elt| result.push(elt));
assert_eq!(&[2, 3, 1, 2, 0], &result[..]);
}
#[test]
fn test_step_replace_unsigned() {
let mut x = 4u32;
let y = x.replace_zero();
assert_eq!(x, 0);
assert_eq!(y, 4);
x = 5;
let y = x.replace_one();
assert_eq!(x, 1);
assert_eq!(y, 5);
}
#[test]
fn test_step_replace_signed() {
let mut x = 4i32;
let y = x.replace_zero();
assert_eq!(x, 0);
assert_eq!(y, 4);
x = 5;
let y = x.replace_one();
assert_eq!(x, 1);
assert_eq!(y, 5);
}
#[test]
fn test_step_replace_no_between() {
let mut x = 4u128;
let y = x.replace_zero();
assert_eq!(x, 0);
assert_eq!(y, 4);
x = 5;
let y = x.replace_one();
assert_eq!(x, 1);
assert_eq!(y, 5);
}
#[test]
fn test_rev_try_folds() {
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!((1..10).rev().try_fold(7, f), (1..10).try_rfold(7, f));
assert_eq!((1..10).rev().try_rfold(7, f), (1..10).try_fold(7, f));
let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
let mut iter = a.iter().rev();
assert_eq!(iter.try_fold(0_i8, |acc, &x| acc.checked_add(x)), None);
assert_eq!(iter.next(), Some(&70));
let mut iter = a.iter().rev();
assert_eq!(iter.try_rfold(0_i8, |acc, &x| acc.checked_add(x)), None);
assert_eq!(iter.next_back(), Some(&60));
}
#[test]
fn test_cloned_try_folds() {
let a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
let f = &|acc, x| i32::checked_add(2 * acc, x);
let f_ref = &|acc, &x| i32::checked_add(2 * acc, x);
assert_eq!(a.iter().cloned().try_fold(7, f), a.iter().try_fold(7, f_ref));
assert_eq!(a.iter().cloned().try_rfold(7, f), a.iter().try_rfold(7, f_ref));
let a = [10, 20, 30, 40, 100, 60, 70, 80, 90];
let mut iter = a.iter().cloned();
assert_eq!(iter.try_fold(0_i8, |acc, x| acc.checked_add(x)), None);
assert_eq!(iter.next(), Some(60));
let mut iter = a.iter().cloned();
assert_eq!(iter.try_rfold(0_i8, |acc, x| acc.checked_add(x)), None);
assert_eq!(iter.next_back(), Some(70));
}
#[test]
fn test_chain_try_folds() {
let c = || (0..10).chain(10..20);
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!(c().try_fold(7, f), (0..20).try_fold(7, f));
assert_eq!(c().try_rfold(7, f), (0..20).rev().try_fold(7, f));
let mut iter = c();
assert_eq!(iter.position(|x| x == 5), Some(5));
assert_eq!(iter.next(), Some(6), "stopped in front, state Both");
assert_eq!(iter.position(|x| x == 13), Some(6));
assert_eq!(iter.next(), Some(14), "stopped in back, state Back");
assert_eq!(iter.try_fold(0, |acc, x| Some(acc + x)), Some((15..20).sum()));
let mut iter = c().rev(); // use rev to access try_rfold
assert_eq!(iter.position(|x| x == 15), Some(4));
assert_eq!(iter.next(), Some(14), "stopped in back, state Both");
assert_eq!(iter.position(|x| x == 5), Some(8));
assert_eq!(iter.next(), Some(4), "stopped in front, state Front");
assert_eq!(iter.try_fold(0, |acc, x| Some(acc + x)), Some((0..4).sum()));
let mut iter = c();
iter.by_ref().rev().nth(14); // skip the last 15, ending in state Front
assert_eq!(iter.try_fold(7, f), (0..5).try_fold(7, f));
let mut iter = c();
iter.nth(14); // skip the first 15, ending in state Back
assert_eq!(iter.try_rfold(7, f), (15..20).try_rfold(7, f));
}
#[test]
fn test_map_try_folds() {
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!((0..10).map(|x| x + 3).try_fold(7, f), (3..13).try_fold(7, f));
assert_eq!((0..10).map(|x| x + 3).try_rfold(7, f), (3..13).try_rfold(7, f));
let mut iter = (0..40).map(|x| x + 10);
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(20));
assert_eq!(iter.try_rfold(0, i8::checked_add), None);
assert_eq!(iter.next_back(), Some(46));
}
#[test]
fn test_filter_try_folds() {
fn p(&x: &i32) -> bool {
0 <= x && x < 10
}
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!((-10..20).filter(p).try_fold(7, f), (0..10).try_fold(7, f));
assert_eq!((-10..20).filter(p).try_rfold(7, f), (0..10).try_rfold(7, f));
let mut iter = (0..40).filter(|&x| x % 2 == 1);
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(25));
assert_eq!(iter.try_rfold(0, i8::checked_add), None);
assert_eq!(iter.next_back(), Some(31));
}
#[test]
fn test_filter_map_try_folds() {
let mp = &|x| if 0 <= x && x < 10 { Some(x * 2) } else { None };
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!((-9..20).filter_map(mp).try_fold(7, f), (0..10).map(|x| 2 * x).try_fold(7, f));
assert_eq!((-9..20).filter_map(mp).try_rfold(7, f), (0..10).map(|x| 2 * x).try_rfold(7, f));
let mut iter = (0..40).filter_map(|x| if x % 2 == 1 { None } else { Some(x * 2 + 10) });
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(38));
assert_eq!(iter.try_rfold(0, i8::checked_add), None);
assert_eq!(iter.next_back(), Some(78));
}
#[test]
fn test_enumerate_try_folds() {
let f = &|acc, (i, x)| usize::checked_add(2 * acc, x / (i + 1) + i);
assert_eq!((9..18).enumerate().try_fold(7, f), (0..9).map(|i| (i, i + 9)).try_fold(7, f));
assert_eq!((9..18).enumerate().try_rfold(7, f), (0..9).map(|i| (i, i + 9)).try_rfold(7, f));
let mut iter = (100..200).enumerate();
let f = &|acc, (i, x)| u8::checked_add(acc, u8::checked_div(x, i as u8 + 1)?);
assert_eq!(iter.try_fold(0, f), None);
assert_eq!(iter.next(), Some((7, 107)));
assert_eq!(iter.try_rfold(0, f), None);
assert_eq!(iter.next_back(), Some((11, 111)));
}
#[test]
fn test_peek_try_folds() {
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!((1..20).peekable().try_fold(7, f), (1..20).try_fold(7, f));
assert_eq!((1..20).peekable().try_rfold(7, f), (1..20).try_rfold(7, f));
let mut iter = (1..20).peekable();
assert_eq!(iter.peek(), Some(&1));
assert_eq!(iter.try_fold(7, f), (1..20).try_fold(7, f));
let mut iter = (1..20).peekable();
assert_eq!(iter.peek(), Some(&1));
assert_eq!(iter.try_rfold(7, f), (1..20).try_rfold(7, f));
let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
assert_eq!(iter.peek(), Some(&100));
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.peek(), Some(&40));
let mut iter = [100, 20, 30, 40, 50, 60, 70].iter().cloned().peekable();
assert_eq!(iter.peek(), Some(&100));
assert_eq!(iter.try_rfold(0, i8::checked_add), None);
assert_eq!(iter.peek(), Some(&100));
assert_eq!(iter.next_back(), Some(50));
let mut iter = (2..5).peekable();
assert_eq!(iter.peek(), Some(&2));
assert_eq!(iter.try_for_each(Err), Err(2));
assert_eq!(iter.peek(), Some(&3));
assert_eq!(iter.try_for_each(Err), Err(3));
assert_eq!(iter.peek(), Some(&4));
assert_eq!(iter.try_for_each(Err), Err(4));
assert_eq!(iter.peek(), None);
assert_eq!(iter.try_for_each(Err), Ok(()));
let mut iter = (2..5).peekable();
assert_eq!(iter.peek(), Some(&2));
assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(4));
assert_eq!(iter.peek(), Some(&2));
assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(3));
assert_eq!(iter.peek(), Some(&2));
assert_eq!(iter.try_rfold((), |(), x| Err(x)), Err(2));
assert_eq!(iter.peek(), None);
assert_eq!(iter.try_rfold((), |(), x| Err(x)), Ok(()));
}
#[test]
fn test_skip_while_try_fold() {
let f = &|acc, x| i32::checked_add(2 * acc, x);
fn p(&x: &i32) -> bool {
(x % 10) <= 5
}
assert_eq!((1..20).skip_while(p).try_fold(7, f), (6..20).try_fold(7, f));
let mut iter = (1..20).skip_while(p);
assert_eq!(iter.nth(5), Some(11));
assert_eq!(iter.try_fold(7, f), (12..20).try_fold(7, f));
let mut iter = (0..50).skip_while(|&x| (x % 20) < 15);
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(23));
}
#[test]
fn test_take_while_folds() {
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!((1..20).take_while(|&x| x != 10).try_fold(7, f), (1..10).try_fold(7, f));
let mut iter = (1..20).take_while(|&x| x != 10);
assert_eq!(iter.try_fold(0, |x, y| Some(x + y)), Some((1..10).sum()));
assert_eq!(iter.next(), None, "flag should be set");
let iter = (1..20).take_while(|&x| x != 10);
assert_eq!(iter.fold(0, |x, y| x + y), (1..10).sum());
let mut iter = (10..50).take_while(|&x| x != 40);
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(20));
}
#[test]
fn test_skip_try_folds() {
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!((1..20).skip(9).try_fold(7, f), (10..20).try_fold(7, f));
assert_eq!((1..20).skip(9).try_rfold(7, f), (10..20).try_rfold(7, f));
let mut iter = (0..30).skip(10);
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(20));
assert_eq!(iter.try_rfold(0, i8::checked_add), None);
assert_eq!(iter.next_back(), Some(24));
}
#[test]
fn test_skip_nth_back() {
let xs = [0, 1, 2, 3, 4, 5];
let mut it = xs.iter().skip(2);
assert_eq!(it.nth_back(0), Some(&5));
assert_eq!(it.nth_back(1), Some(&3));
assert_eq!(it.nth_back(0), Some(&2));
assert_eq!(it.nth_back(0), None);
let ys = [2, 3, 4, 5];
let mut ity = ys.iter();
let mut it = xs.iter().skip(2);
assert_eq!(it.nth_back(1), ity.nth_back(1));
assert_eq!(it.clone().nth(0), ity.clone().nth(0));
assert_eq!(it.nth_back(0), ity.nth_back(0));
assert_eq!(it.clone().nth(0), ity.clone().nth(0));
assert_eq!(it.nth_back(0), ity.nth_back(0));
assert_eq!(it.clone().nth(0), ity.clone().nth(0));
assert_eq!(it.nth_back(0), ity.nth_back(0));
assert_eq!(it.clone().nth(0), ity.clone().nth(0));
let mut it = xs.iter().skip(2);
assert_eq!(it.nth_back(4), None);
assert_eq!(it.nth_back(0), None);
let mut it = xs.iter();
it.by_ref().skip(2).nth_back(3);
assert_eq!(it.next_back(), Some(&1));
let mut it = xs.iter();
it.by_ref().skip(2).nth_back(10);
assert_eq!(it.next_back(), Some(&1));
}
#[test]
fn test_take_try_folds() {
let f = &|acc, x| i32::checked_add(2 * acc, x);
assert_eq!((10..30).take(10).try_fold(7, f), (10..20).try_fold(7, f));
assert_eq!((10..30).take(10).try_rfold(7, f), (10..20).try_rfold(7, f));
let mut iter = (10..30).take(20);
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(20));
assert_eq!(iter.try_rfold(0, i8::checked_add), None);
assert_eq!(iter.next_back(), Some(24));
let mut iter = (2..20).take(3);
assert_eq!(iter.try_for_each(Err), Err(2));
assert_eq!(iter.try_for_each(Err), Err(3));
assert_eq!(iter.try_for_each(Err), Err(4));
assert_eq!(iter.try_for_each(Err), Ok(()));
let mut iter = (2..20).take(3).rev();
assert_eq!(iter.try_for_each(Err), Err(4));
assert_eq!(iter.try_for_each(Err), Err(3));
assert_eq!(iter.try_for_each(Err), Err(2));
assert_eq!(iter.try_for_each(Err), Ok(()));
}
#[test]
fn test_flat_map_try_folds() {
let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
let mr = &|x| (5 * x)..(5 * x + 5);
assert_eq!((0..10).flat_map(mr).try_fold(7, f), (0..50).try_fold(7, f));
assert_eq!((0..10).flat_map(mr).try_rfold(7, f), (0..50).try_rfold(7, f));
let mut iter = (0..10).flat_map(mr);
iter.next();
iter.next_back(); // have front and back iters in progress
assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
let mut iter = (0..10).flat_map(|x| (4 * x)..(4 * x + 4));
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(17));
assert_eq!(iter.try_rfold(0, i8::checked_add), None);
assert_eq!(iter.next_back(), Some(35));
}
#[test]
fn test_flatten_try_folds() {
let f = &|acc, x| i32::checked_add(acc * 2 / 3, x);
let mr = &|x| (5 * x)..(5 * x + 5);
assert_eq!((0..10).map(mr).flatten().try_fold(7, f), (0..50).try_fold(7, f));
assert_eq!((0..10).map(mr).flatten().try_rfold(7, f), (0..50).try_rfold(7, f));
let mut iter = (0..10).map(mr).flatten();
iter.next();
iter.next_back(); // have front and back iters in progress
assert_eq!(iter.try_rfold(7, f), (1..49).try_rfold(7, f));
let mut iter = (0..10).map(|x| (4 * x)..(4 * x + 4)).flatten();
assert_eq!(iter.try_fold(0, i8::checked_add), None);
assert_eq!(iter.next(), Some(17));
assert_eq!(iter.try_rfold(0, i8::checked_add), None);
assert_eq!(iter.next_back(), Some(35));
}
#[test]
fn test_functor_laws() {
// identity:
fn identity<T>(x: T) -> T {
x
}
assert_eq!((0..10).map(identity).sum::<usize>(), (0..10).sum());
// composition:
fn f(x: usize) -> usize {
x + 3
}
fn g(x: usize) -> usize {
x * 2
}
fn h(x: usize) -> usize {
g(f(x))
}
assert_eq!((0..10).map(f).map(g).sum::<usize>(), (0..10).map(h).sum());
}
#[test]
fn test_monad_laws_left_identity() {
fn f(x: usize) -> impl Iterator<Item = usize> {
(0..10).map(move |y| x * y)
}
assert_eq!(once(42).flat_map(f.clone()).sum::<usize>(), f(42).sum());
}
#[test]
fn test_monad_laws_right_identity() {
assert_eq!((0..10).flat_map(|x| once(x)).sum::<usize>(), (0..10).sum());
}
#[test]
fn test_monad_laws_associativity() {
fn f(x: usize) -> impl Iterator<Item = usize> {
0..x
}
fn g(x: usize) -> impl Iterator<Item = usize> {
(0..x).rev()
}
assert_eq!(
(0..10).flat_map(f).flat_map(g).sum::<usize>(),
(0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>()
);
}
#[test]
fn test_is_sorted() {
assert!([1, 2, 2, 9].iter().is_sorted());
assert!(![1, 3, 2].iter().is_sorted());
assert!([0].iter().is_sorted());
assert!(std::iter::empty::<i32>().is_sorted());
assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
assert!([-2, -1, 0, 3].iter().is_sorted());
assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
assert!(!["c", "bb", "aaa"].iter().is_sorted());
assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
}
#[test]
fn test_partition() {
fn check(xs: &mut [i32], ref p: impl Fn(&i32) -> bool, expected: usize) {
let i = xs.iter_mut().partition_in_place(p);
assert_eq!(expected, i);
assert!(xs[..i].iter().all(p));
assert!(!xs[i..].iter().any(p));
assert!(xs.iter().is_partitioned(p));
if i == 0 || i == xs.len() {
assert!(xs.iter().rev().is_partitioned(p));
} else {
assert!(!xs.iter().rev().is_partitioned(p));
}
}
check(&mut [], |_| true, 0);
check(&mut [], |_| false, 0);
check(&mut [0], |_| true, 1);
check(&mut [0], |_| false, 0);
check(&mut [-1, 1], |&x| x > 0, 1);
check(&mut [-1, 1], |&x| x < 0, 1);
let ref mut xs = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
check(xs, |_| true, 10);
check(xs, |_| false, 0);
check(xs, |&x| x % 2 == 0, 5); // evens
check(xs, |&x| x % 2 == 1, 5); // odds
check(xs, |&x| x % 3 == 0, 4); // multiple of 3
check(xs, |&x| x % 4 == 0, 3); // multiple of 4
check(xs, |&x| x % 5 == 0, 2); // multiple of 5
check(xs, |&x| x < 3, 3); // small
check(xs, |&x| x > 6, 3); // large
}