feat(corelib): Iterator::find

[julio4]

Searches for an element of an iterator that satisfies a predicate.

find() takes a closure that returns true or false. It applies this closure to each element of the iterator, and if any of them return true, then find() returns Some(element). If they all return false, it returns None.

find() is short-circuiting; in other words, it will stop processing as soon as the closure returns true.

Examples

Basic usage:

let mut iter = array![1, 2, 3].into_iter();

assert_eq!(iter.find(|x| x == 2), Option::Some(2));

assert_eq!(iter.find(|x| x == 5), Option::None);

Stopping at the first true:

let mut iter = array![1, 2, 3].into_iter();

assert_eq!(iter.find(|x| x == 2), Option::Some(2));

// we can still use `iter`, as there are more elements.
assert_eq!(iter.next(), Option::Some(3));

[reviewable-StarkWare]

This change is 

[orizi]

Reviewed all commit messages.
Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @julio4)

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corelib/src/iter/traits/iterator.cairo line 359 at r1 (raw file):

            },
        }
    }

Suggestion:

    fn find<
        P,
        +core::ops::Fn<P, (@Self::Item,)>[Output: bool],
        +Destruct<P>,
        +Destruct<T>,
        +Destruct<Self::Item>,
    >(
        ref self: T, predicate: P,
    ) -> Option<
        Self::Item,
    > {
        match Self::next(ref self) {
            Option::None => Option::None,
            Option::Some(x) => if predicate(@x) {
                Option::Some(x)
            } else {
                Self::find(ref self, predicate)
            },
        }
    }

[julio4]

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @orizi)

---

corelib/src/iter/traits/iterator.cairo line 359 at r1 (raw file):

            },
        }
    }

Done.

[orizi]

Reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @julio4)

---

a discussion (no related file):
@gilbens-starkware @ilyalesokhin-starkware for 2nd eye.

[gilbens-starkware]

Reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @julio4)