package travesty

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package travesty
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Extend0_predicate creates extensions for a Container.S0 over predicates.

Parameters

module P : Core_kernel.T
module C : Core_kernel.Container.S0 with type elt = P.t -> bool

Signature

include Extensions0 with type t := C.t and type elt := P.t -> Base.bool
include Types_intf.S0 with type t := C.t with type elt := P.t -> Base.bool
include Generic_extensions with type 'a t := C.t and type 'a elt := P.t -> Base.bool

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 Types_intf.Generic with type 'a t := C.t with type 'a elt := P.t -> Base.bool

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).

val at_most_one : C.t -> (P.t -> Base.bool) 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:

T_list.at_most_one []     (* ok None *)
       at_most_one [1]    (* ok (Some 1) *)
       at_most_one [1; 2] (* error -- too many *)
val one : C.t -> (P.t -> Base.bool) Base.Or_error.t

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

Examples:

T_list.one []     (* error -- not enough *)
       one [1]    (* ok 1 *)
       one [1; 2] (* error -- too many *)
val two : C.t -> ((P.t -> Base.bool) * (P.t -> Base.bool)) 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:

T_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

val max_measure : measure:((P.t -> Base.bool) -> Base.int) -> ?default:Base.int -> 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.

include Generic_predicate_extensions with type 'a t := C.t and type 'a item := P.t
val any : P.t -> predicates: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.

val all : P.t -> predicates: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.

val none : P.t -> predicates: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.

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