use core::cell::Cell;
use core::convert::TryFrom;
+use core::iter::TrustedRandomAccess;
use core::iter::*;
/// An iterator wrapper that panics whenever `next` or `next_back` is called
assert_eq!(b, vec![200, 300, 400]);
}
+#[test]
+fn test_zip_trusted_random_access_composition() {
+ let a = [0, 1, 2, 3, 4];
+ let b = a;
+ let c = a;
+
+ let a = a.iter().copied();
+ let b = b.iter().copied();
+ let mut c = c.iter().copied();
+ c.next();
+
+ let mut z1 = a.zip(b);
+ assert_eq!(z1.next().unwrap(), (0, 0));
+
+ let mut z2 = z1.zip(c);
+ fn assert_trusted_random_access<T: TrustedRandomAccess>(_a: &T) {}
+ assert_trusted_random_access(&z2);
+ assert_eq!(z2.next().unwrap(), ((1, 1), 1));
+}
+
#[test]
fn test_iterator_step_by() {
// Identity
assert_eq!([].iter().intersperse(&()).size_hint(), (0, Some(0)));
}
+#[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 = vec![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_fold_specialization_intersperse() {
let mut iter = (1..2).intersperse(0);