Source file CCFun.ml

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(* This file is free software, part of containers. See file "license" for more details. *)

(** {1 Basic Functions} *)

let opaque_identity x = x

(* import standard implementations, if any *)

include Sys
include CCShims_.Stdlib

[@@@ifge 4.8]

include Fun

[@@@else_]

external id : 'a -> 'a = "%identity"
let[@inline] flip f x y = f y x
let[@inline] const x _ = x
let[@inline] negate f x = not (f x)
let[@inline] protect ~finally f =
  try
    let x= f() in
    finally();
    x
  with e ->
    finally();
    raise e

[@@@endif]

let compose f g x = g (f x)

let compose_binop f g x y = g (f x) (f y)

let curry f x y = f (x,y)

let uncurry f (x,y) = f x y

let tap f x = ignore (f x); x

let lexicographic f1 f2 x y =
  let c = f1 x y in
  if c <> 0 then c else f2 x y

let finally ~h ~f =
  try
    let x = f () in
    ignore (h ());
    x
  with e ->
    ignore (h ());
    raise e

let finally1 ~h f x =
  try
    let res = f x in
    ignore (h ());
    res
  with e ->
    ignore (h ());
    raise e

let finally2 ~h f x y =
  try
    let res = f x y in
    ignore (h ());
    res
  with e ->
    ignore (h ());
    raise e

let rec iterate n f x =
  if n < 0 then
    invalid_arg "CCFun.iterate"
  else if n = 0 then
    x
  else
    iterate (n - 1) f (f x)

(*$= iterate & ~printer:Q.Print.int
  10 (iterate 0 succ 10)
  11 (iterate 1 succ 10)
  12 (iterate 2 succ 10)
  15 (iterate 5 succ 10)
*)
(*$R
  assert_raises
  (Invalid_argument "CCFun.iterate")
  (fun () -> iterate (-1) succ 10)
*)

module Infix = struct
  (* default implem for some operators *)
  let (|>) x f = f x
  let (@@) f x = f x

  let (%>) = compose
  let (%) f g x = f (g x)
end

(*$T
  CCFun.((succ %> string_of_int) 2 = "3")
  CCFun.((( * ) 3 % succ) 5 = 18)
  CCFun.(succ @@ ( * ) 2 @@ pred @@ 3 = 5)
  CCFun.(3 |> succ |> ( * ) 5 |> pred = 19)
*)

include Infix

module Monad(X : sig type t end) = struct
  type 'a t = X.t -> 'a
  let return x _ = x
  let (>|=) f g x = g (f x)
  let (>>=) f g x = g (f x) x
end