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use core::iter::*;
#[test]
fn test_intersperse() {
let v = std::iter::empty().intersperse(0u32).collect::<Vec<_>>();
assert_eq!(v, vec![]);
let v = std::iter::once(1).intersperse(0).collect::<Vec<_>>();
assert_eq!(v, vec![1]);
let xs = ["a", "", "b", "c"];
let v: Vec<&str> = xs.iter().map(|x| *x).intersperse(", ").collect();
let text: String = v.concat();
assert_eq!(text, "a, , b, c".to_string());
let ys = [0, 1, 2, 3];
let mut it = ys[..0].iter().map(|x| *x).intersperse(1);
assert!(it.next() == None);
}
#[test]
fn test_intersperse_size_hint() {
let iter = std::iter::empty::<i32>().intersperse(0);
assert_eq!(iter.size_hint(), (0, Some(0)));
let xs = ["a", "", "b", "c"];
let mut iter = xs.iter().map(|x| *x).intersperse(", ");
assert_eq!(iter.size_hint(), (7, Some(7)));
assert_eq!(iter.next(), Some("a"));
assert_eq!(iter.size_hint(), (6, Some(6)));
assert_eq!(iter.next(), Some(", "));
assert_eq!(iter.size_hint(), (5, Some(5)));
assert_eq!([].iter().intersperse(&()).size_hint(), (0, Some(0)));
}
#[test]
fn test_fold_specialization_intersperse() {
let mut iter = (1..2).intersperse(0);
iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
let mut iter = (1..3).intersperse(0);
iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
let mut iter = (1..4).intersperse(0);
iter.clone().for_each(|x| assert_eq!(Some(x), iter.next()));
}
#[test]
fn test_try_fold_specialization_intersperse_ok() {
let mut iter = (1..2).intersperse(0);
iter.clone().try_for_each(|x| {
assert_eq!(Some(x), iter.next());
Some(())
});
let mut iter = (1..3).intersperse(0);
iter.clone().try_for_each(|x| {
assert_eq!(Some(x), iter.next());
Some(())
});
let mut iter = (1..4).intersperse(0);
iter.clone().try_for_each(|x| {
assert_eq!(Some(x), iter.next());
Some(())
});
}
#[test]
fn test_intersperse_with() {
#[derive(PartialEq, Debug)]
struct NotClone {
u: u32,
}
let r = [NotClone { u: 0 }, NotClone { u: 1 }]
.into_iter()
.intersperse_with(|| NotClone { u: 2 })
.collect::<Vec<_>>();
assert_eq!(r, vec![NotClone { u: 0 }, NotClone { u: 2 }, NotClone { u: 1 }]);
let mut ctr = 100;
let separator = || {
ctr *= 2;
ctr
};
let r = (0..3).intersperse_with(separator).collect::<Vec<_>>();
assert_eq!(r, vec![0, 200, 1, 400, 2]);
}
#[test]
fn test_intersperse_fold() {
let v = (1..4).intersperse(9).fold(Vec::new(), |mut acc, x| {
acc.push(x);
acc
});
assert_eq!(v.as_slice(), [1, 9, 2, 9, 3]);
let mut iter = (1..4).intersperse(9);
assert_eq!(iter.next(), Some(1));
let v = iter.fold(Vec::new(), |mut acc, x| {
acc.push(x);
acc
});
assert_eq!(v.as_slice(), [9, 2, 9, 3]);
struct NoneAtStart(i32); // Produces: None, Some(2), Some(3), None, ...
impl Iterator for NoneAtStart {
type Item = i32;
fn next(&mut self) -> Option<i32> {
self.0 += 1;
Some(self.0).filter(|i| i % 3 != 1)
}
}
let v = NoneAtStart(0).intersperse(1000).fold(0, |a, b| a + b);
assert_eq!(v, 0);
}
#[test]
fn test_intersperse_collect_string() {
let contents = [1, 2, 3];
let contents_string = contents
.into_iter()
.map(|id| id.to_string())
.intersperse(", ".to_owned())
.collect::<String>();
assert_eq!(contents_string, "1, 2, 3");
}
#[test]
fn test_try_fold_specialization_intersperse_err() {
let orig_iter = ["a", "b"].iter().copied().intersperse("-");
// Abort after the first item.
let mut iter = orig_iter.clone();
iter.try_for_each(|_| None::<()>);
assert_eq!(iter.next(), Some("-"));
assert_eq!(iter.next(), Some("b"));
assert_eq!(iter.next(), None);
// Abort after the second item.
let mut iter = orig_iter.clone();
iter.try_for_each(|item| if item == "-" { None } else { Some(()) });
assert_eq!(iter.next(), Some("b"));
assert_eq!(iter.next(), None);
// Abort after the third item.
let mut iter = orig_iter.clone();
iter.try_for_each(|item| if item == "b" { None } else { Some(()) });
assert_eq!(iter.next(), None);
}
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