find p l returns Some x where x is the first element of l such as p x returns true or None if such an element has not been found.

rfind p l returns Some x where x is the last element of l such that p x returns true or None if such element as not been found.

findi p l returns Some (i, ai) where ai and i are respectively the first element of l and its index, such that p i ai is true, or None if no such element has been found.

Whenever n is inside of l size bounds, split_at n l returns Ok(l1,l2), where l1 contains the first n elements of l and l2 contains the others. Otherwise, returns `Invalid_argument n.

If n is inside the bounds of l, at l n returns Ok x, where x is the n-th element of the list l. Otherwise, returns Error (`Invalid_argument(n)).

assoc a l returns Some b where b is the value associated with key b in the list of pairs l. That is, assoc a [ ...; (a,b); ...] = Some b if (a,b) is the leftmost binding of a in list l. Return None if there is no value associated with a in the list l.

assoc_inv b l returns Some a where a is the key associated with value b in the list of pairs l. That is, assoc b [ ...; (a,b); ...] = Some a if (a,b) is the leftmost binding of a in list l. Return None if there is no key associated with b in the list l.

As assoc but with physical equality.

find_map f xs returns Some y such that x is the first element of the list where f x returns Some y. It returns None if no such element exists.

hd l returns Some x such that x is the first element of the given list l. Returns None if list l is empty.

tl l returns Some x such that x is the given list l without its first element. Returns None if list l is empty.

last l returns either Some x where x is the last element of the list, or None if the list is empty. This function takes linear time.

reduce f h::t is Some (fold_left f h t) and reduce f [] is None.

min_max l returns either Some(s, l) where s and l are respectively the smallest and biggest element of l as judged by Pervasives.compare (by default) or None if l is empty. You can provide another comparison function via the optional cmp parameter.

max l returns either Some x where x is the largest value of the list as judged by Pervasives.compare (by default) or None is the list is empty. You can provide another comparison function via the optional cmp parameter.

min l returns either Some x where x is the smallest value of the list as judged by Pervasives.compare or None is the list is empty. You can provide another comparison function via the optional cmp parameter.