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use core::iter::*;
#[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 = "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 >> (usize::BITS / 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_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));
}
|
