`val index_of : 'a t -> 'a -> int`

Return the index (position : 0 starting) of an element in a ref list, using ( = ) for testing element equality raise `Not_found` if no element was found

`val index : ('a -> bool) -> 'a t -> int`

Return the index (position : 0 starting) of an element in a ref list, using the specified comparator raise `Not_found` if no element was found

`val at_index : 'a t -> int -> 'a`

Return the element of ref list at the specified index raise `Invalid_index` if the index is outside `0 ; length-1`

`val set : 'a t -> int -> 'a -> unit`

Change the element at the specified index raise `Invalid_index` if the index is outside `0 ; length-1`

`val remove_at : 'a t -> int -> unit`

Remove the element at the specified index raise `Invalid_index` if the index is outside `0 ; length-1`