From f57dc38c05f3b8b002b8daa823a21ad25f5d682d Mon Sep 17 00:00:00 2001

From: "Richard W.M. Jones" <rjones@redhat.com>

Date: Tue, 10 Nov 2015 20:07:56 +0000

Subject: [PATCH 2/5] mllib: Add Common_utils 'may' function.

This higher order function encapsulates the following pattern:

  match x with

  | None -> ()

  | Some x -> f x

(replaced with: `may f x`)

This is taken from OCaml lablgtk (Gtk bindings) where this pattern is

used frequently.

See also: https://ocaml.org/learn/tutorials/labels.html

(cherry picked from commit 9a2c5b7c4d367aae665ab66f85e463f9d244e465)

---

 mllib/common_utils.ml  | 4 ++++

 mllib/common_utils.mli | 3 +++

 2 files changed, 7 insertions(+)

diff --git a/mllib/common_utils.ml b/mllib/common_utils.ml

index c714cb3..dfee615 100644

--- a/mllib/common_utils.ml

+++ b/mllib/common_utils.ml

@@ -254,6 +254,10 @@ let rec assoc ?(cmp = compare) ~default x = function

   | (y, y') :: _ when cmp x y = 0 -> y'

   | _ :: ys -> assoc ~cmp ~default x ys

+let may f = function

+  | None -> ()

+  | Some x -> f x

+

 let istty chan =

   Unix.isatty (Unix.descr_of_out_channel chan)

diff --git a/mllib/common_utils.mli b/mllib/common_utils.mli

index 39e05a1..081e4a4 100644

--- a/mllib/common_utils.mli

+++ b/mllib/common_utils.mli

@@ -65,6 +65,9 @@ val assoc : ?cmp:('a -> 'a -> int) -> default:'b -> 'a -> ('a * 'b) list -> 'b

 (** Like {!List.assoc} but with a user-defined comparison function, and

     instead of raising [Not_found], it returns the [~default] value. *)

+val may : ('a -> unit) -> 'a option -> unit

+(** [may f (Some x)] runs [f x].  [may f None] does nothing. *)

+

 val prog : string

 (** The program name (derived from {!Sys.executable_name}). *)

-- 

2.5.0