Module Container_exts.Extend1Source

Extend1 creates extensions for a Container.S1.

Parameters

Signature

include Container_exts_types.Generic with type 'a t := 'a C.t and type 'a elt := 'a

Generic_extensions refers to the container type as 'a t, and the element type as 'a elt; substitute t/elt (arity-0) or 'a t/'a (arity-1) accordingly below.

include Generic_types.Generic with type 'a t := 'a C.t with type 'a elt := 'a

Testing for a specific number of elements

The following functions help in checking whether a container has a particular, commonly-required number of elements (zero or one, one, two, and so on).

Sourceval at_most_one : 'a C.t -> 'a Base.option Base.Or_error.t

at_most_one xs returns Ok None if xs is empty; Ok Some(x) if it contains only x; and an error otherwise.

Examples (using an extended version of List):

  List.at_most_one [] (* ok None *) at_most_one
    [1] (* ok (Some 1) *)
    at_most_one [1; 2]

  (* error -- too many *)
Sourceval one : 'a C.t -> 'a Base.Or_error.t

one xs returns Ok x if xs contains only x, and an error otherwise.

Examples (using an extended version of List):

  List.one [] (* error -- not enough *) one [1] (* ok 1 *) one [1; 2]

  (* error -- too many *)
Sourceval two : 'a C.t -> ('a * 'a) Base.Or_error.t

two xs returns Ok (x, y) if xs is a list containing only x and y in that order, and an error otherwise.

Examples (using an extended version of List):

  List.two [] (* error -- not enough *) two
    [1] (* error -- not enough *)
    two
    [1; 2] (* ok (1, 2) *)
    two [1; 2; 3]

  (* error -- too many *)

Miscellaneous extensions

Sourceval max_measure : measure:('a -> Base.int) -> ?default:Base.int -> 'a C.t -> Base.int

max_measure ~measure ~default xs measures each item in xs according to measure, and returns the highest measure reported. If xs is empty, return default if given, and 0 otherwise.

Predicate extensions are available on all arity-1 containers, provided that we fix the element type parameter to 'a -> bool.

include Container_exts_types.Generic_predicate with type 'a t := ('a -> Base.bool) C.t and type 'a item := 'a
Sourceval any : 'a -> predicates:('a -> Base.bool) C.t -> Base.bool

any x ~predicates tests x against predicates until one returns true, in which case it returns true; or all return false, in which case it returns false.

Sourceval all : 'a -> predicates:('a -> Base.bool) C.t -> Base.bool

any x ~predicates tests x against predicates until one returns false, in which case it returns false; or all return true, in which case it returns true.

Sourceval none : 'a -> predicates:('a -> Base.bool) C.t -> Base.bool

none x ~predicates is the same as any x with all predicates in predicates negated. It tests x against predicates until one returns true, in which case it returns false; or all return false, in which case it returns true.