This module implements functional arrays equipped with accessors that cannot raise exceptions following the same design principles as FallbackArray:
Reading out of the bounds of the arrays return a fallback value fixed at array construction time, writing out of the bounds of the arrays is ignored.
Contrary to FallbackArray, writing generates a fresh array.
Please notice that this implementation is naive and should only be used for small arrays. If there is a need for large functional arrays, it is recommended to implement Backer's trick to get constant-time reads and writes for sequences of mutations applied to the same array.
val make : int -> 'a -> 'a tmake len v builds an array a initializing len cells with v. The value v is the fallback value for a.
val init : int -> 'a -> (int -> 'a) -> 'a tinit len v make builds an array a initializing len cells where the i-th cell value is make i. The value v is the fallback value for a.
val fallback : 'a t -> 'afallback a returns the fallback value for a.
val length : 'a t -> intlength a returns the length of a.
val get : 'a t -> int -> 'aget a idx returns the contents of the cell of index idx in a. If idx < 0 or idx >= length a, get a idx = fallback a.
set a idx value returns a new array identical to a except that the cell of index idx with value. If idx < 0 or idx >= length a, returns a copy of a.
val iter : ('a -> unit) -> 'a t -> unititer f a iterates f over the cells of a from the cell indexed 0 to the cell indexed length a - 1.
val iteri : (int -> 'a -> unit) -> 'a t -> unititeri f a iterates f over the cells of a from the cell indexed 0 to the cell indexed length a - 1 passing the cell index to f.
map a computes a new array obtained by applying f to each cell contents of a. Notice that the fallback value of the new array is f (fallback a).
mapi f a computes a new array obtained by applying f to each cell contents of a passing the index of this cell to i. Notice that the fallback value of the new array is f (-1) (fallback a).
val fold : ('b -> 'a -> 'b) -> 'a t -> 'b -> 'bfold f a init traverses a from the cell indexed 0 to the cell indexed length a - 1 and transforms accu into f accu x where x is the content of the cell under focus. accu is init on the first iteration.
fold_map f a init fallback traverses a from the cell indexed 0 to the cell indexed length a - 1 and transforms accu into fst (f accu x) where x is the content of the cell under focus. accu is init on the first iteration. The function also returns a fresh array containing snd (f accu x) for each x. fallback is required to initialize a fresh array before it can be filled.