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use itertools::Itertools;
struct PanickingCounter {
curr: usize,
max: usize,
}
impl Iterator for PanickingCounter {
type Item = ();
fn next(&mut self) -> Option<Self::Item> {
self.curr += 1;
assert_ne!(
self.curr, self.max,
"Input iterator reached maximum of {} suggesting collection by adaptor",
self.max
);
Some(())
}
}
fn no_collect_test<A, T>(to_adaptor: T)
where A: Iterator, T: Fn(PanickingCounter) -> A
{
let counter = PanickingCounter { curr: 0, max: 10_000 };
let adaptor = to_adaptor(counter);
for _ in adaptor.take(5) {}
}
#[test]
fn permutations_no_collect() {
no_collect_test(|iter| iter.permutations(5))
}
#[test]
fn combinations_no_collect() {
no_collect_test(|iter| iter.combinations(5))
}
#[test]
fn combinations_with_replacement_no_collect() {
no_collect_test(|iter| iter.combinations_with_replacement(5))
}