Function discard_while 

pub fn discard_while<T>(
    iter: impl IntoIterator<Item = T>,
    cond: impl FnMut(&T) -> bool,
) -> (Option<T>, usize)

Advance an iterator as long as a condition on the yielded items holds. Returns the first item that no longer satisfies the condition, if any, and the number of items discarded.

This is similar to a combination of find and position.

Note: This function takes any implementation of IntoIterator, which includes iterators themselves and mutable references to them.

Overflow Behavior

The method does no guarding against overflows, so if there are more than usize::MAX non-matching elements, it either produces the wrong result or panics. If overflow checks are enabled, a panic is guaranteed.

Panics

This function might panic if the iterator has more than usize::MAX non-matching elements.

Examples

Basic usage:

let mut range = 1..=10;
let result = discard_while(&mut range, |&n| n != 5);
assert_eq!(result, (Some(5), 4));
assert_eq!(range, 6..=10);

If the iterator ends before an item that does not fulfill the condition is encountered, None is returned as the first return value.

let arr = [6, 5, 4, 3, 2, 1];
let result = discard_while(arr, |&n| true);
assert_eq!(result, (None, 6));

If the first element that is encountered does not fulfill the condition, 0 is returned as the second return value.

let mut range = 2..=8;
let result = discard_while(&mut range, |&n| false);
assert_eq!(result, (Some(2), 0));
assert_eq!(range, 3..=8);