package core_kernel

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  1. Make Functors
package core_kernel
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Comparable extends Base.Comparable and provides functions for comparing like types.

Usage example:

module Foo = struct
  module T = struct
    type t = ... [@@deriving compare, sexp]
  end
  include T
  include Comparable.Make (T)
end

Then include Comparable.S in the signature (see Comparable_intf for an example).

To add an Infix submodule:

module C = Comparable.Make (T)
include C
module Infix = (C : Comparable.Infix with type t := t)

Common pattern: Define a module O with a restricted signature. It aims to be (locally) opened to bring useful operators into scope without shadowing unexpected variable names. E.g. in the Date module:

module O = struct
  include (C : Comparable.Infix with type t := t)
  let to_string t = ..
end

Opening Date would shadow now, but opening Date.O doesn't:

let now = .. in
let someday = .. in
Date.O.(now > someday)
module type Infix = Comparable.Infix
module type Polymorphic_compare = Comparable.Polymorphic_compare
module type S = Comparable.S
module type Validate = Comparable.Validate
module type With_zero = Comparable.With_zero
val lexicographic : ('a -> 'a -> int) list -> 'a -> 'a -> int

lexicographic cmps x y compares x and y lexicographically using functions in the list cmps.

val lift : ('a -> 'a -> 'int_or_bool) -> f:('b -> 'a) -> 'b -> 'b -> 'int_or_bool

lift cmp ~f x y compares x and y by comparing f x and f y via cmp.

module Inherit (C : sig ... end) (T : sig ... end) : sig ... end

Inherit comparability from a component.

Make Functors

The Comparable Make functor family allows users to choose among the following attributes:

  • *_using_comparator or not
  • *_binable or not
  • *_plain or not

Thus there are functors like Make_plain or Make_binable_using_comparator, etc.

module Make_plain (T : sig ... end) : sig ... end
module Make (T : sig ... end) : sig ... end
module Make_plain_using_comparator (T : sig ... end) : sig ... end
module Make_using_comparator (T : sig ... end) : sig ... end
module Make_binable (T : sig ... end) : sig ... end
module Make_binable_using_comparator (T : sig ... end) : sig ... end
module Extend (M : Base.Comparable.S) (X : sig ... end) : sig ... end
module Extend_binable (M : Base.Comparable.S) (X : sig ... end) : sig ... end
module Map_and_set_binable (T : sig ... end) : sig ... end
module Map_and_set_binable_using_comparator (T : sig ... end) : sig ... end
module Poly (T : sig ... end) : sig ... end
module Validate = Comparable.Validate
module With_zero = Comparable.With_zero
module Validate_with_zero (T : sig ... end) : sig ... end

The following module types and functors may be used to define stable modules:

module Stable : sig ... end
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