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use core::iter::*;
#[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_take_advance_by() {
let mut take = (0..10).take(3);
assert_eq!(take.advance_by(2), Ok(()));
assert_eq!(take.next(), Some(2));
assert_eq!(take.advance_by(1), Err(0));
assert_eq!((0..0).take(10).advance_by(0), Ok(()));
assert_eq!((0..0).take(10).advance_by(1), Err(0));
assert_eq!((0..10).take(4).advance_by(5), Err(4));
let mut take = (0..10).take(3);
assert_eq!(take.advance_back_by(2), Ok(()));
assert_eq!(take.next(), Some(0));
assert_eq!(take.advance_back_by(1), Err(0));
assert_eq!((0..2).take(1).advance_back_by(10), Err(1));
assert_eq!((0..0).take(1).advance_back_by(1), Err(0));
assert_eq!((0..0).take(1).advance_back_by(0), Ok(()));
assert_eq!((0..usize::MAX).take(100).advance_back_by(usize::MAX), Err(100));
}
#[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_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(()));
}
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