[Libguestfs] [PATCH 1/4] mllib: Add Common_utils 'may' function.

[Richard W.M. Jones]

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
---
 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 d654fa8..52079d2 100644
--- a/mllib/common_utils.ml
+++ b/mllib/common_utils.ml
@@ -267,6 +267,10 @@ 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 6e08e43..d8f63d5 100644
--- a/mllib/common_utils.mli
+++ b/mllib/common_utils.mli
@@ -124,6 +124,9 @@ 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