From: Matthias Goergens <matthias.goergens@citrix.com>
Date: Tue, 2 Feb 2010 16:07:11 +0000 (+0000)
Subject: Adds `join' to the Opt module
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=5a2b1eaffba59dc6459e18f735616f9f5fa70909;p=xcp%2Fxen-api-libs.git

Adds `join' to the Opt module

`join' collapses (Some (Some a)) down to (Some a), and gives Nothing otherwise.

Signed-off-by: Matthias Goergens <matthias.goergens@citrix.com>
---

diff --git a/stdext/opt.ml b/stdext/opt.ml
index 3175208..8c39fb1 100644
--- a/stdext/opt.ml
+++ b/stdext/opt.ml
@@ -54,3 +54,8 @@ let fold_right f opt accu =
 	| None -> accu
 
 let cat_options a = List.map unbox (List.filter is_boxed a)
+
+let join = function
+    | Some (Some a) -> Some a
+    | _ -> None
+
diff --git a/stdext/opt.mli b/stdext/opt.mli
index aafa63e..fd3147c 100644
--- a/stdext/opt.mli
+++ b/stdext/opt.mli
@@ -20,3 +20,4 @@ val to_list : 'a option -> 'a list
 val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b option -> 'a
 val fold_right : ('a -> 'b -> 'b) -> 'a option -> 'b -> 'b
 val cat_options : 'a option list -> 'a list
+val join : ('a option) option -> 'a option