From: Enrico Tassi <enrico.tassi@inria.fr>
Date: Thu, 25 Jun 2009 15:10:43 +0000 (+0000)
Subject: new function
X-Git-Tag: make_still_working~3796
X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=commitdiff_plain;h=571d199acd4e6743a48f8f64f28c62d18182d04d;p=helm.git

new function
---

diff --git a/helm/software/components/extlib/hExtlib.ml b/helm/software/components/extlib/hExtlib.ml
index 49d28bbb9..cccb46767 100644
--- a/helm/software/components/extlib/hExtlib.ml
+++ b/helm/software/components/extlib/hExtlib.ml
@@ -237,6 +237,18 @@ let filter_map_acc f acc l =
    acc, List.rev res
 ;;
 
+let filter_map_monad f acc l =
+  let acc, res = 
+   List.fold_left
+    (fun (acc, res) t ->
+       match f acc t with
+       | acc, None -> acc, res
+       | acc, Some x -> acc, x::res)
+    (acc,[]) l
+  in
+   acc, List.rev res
+;;
+
 let list_rev_map_filter f l =
    let rec aux a = function
       | []       -> a
diff --git a/helm/software/components/extlib/hExtlib.mli b/helm/software/components/extlib/hExtlib.mli
index 63bfc25f1..9c0980f76 100644
--- a/helm/software/components/extlib/hExtlib.mli
+++ b/helm/software/components/extlib/hExtlib.mli
@@ -86,6 +86,8 @@ val list_uniq:
 val filter_map: ('a -> 'b option) -> 'a list -> 'b list (** filter + map *)
 val filter_map_acc: ('acc -> 'a -> ('acc * 'b) option) -> 'acc -> 'a list ->
         'acc * 'b list (** fold/filter + map *)
+val filter_map_monad: ('acc -> 'a -> 'acc * 'b option) -> 'acc -> 'a list ->
+        'acc * 'b list (** fold/filter + map *)
 
 val list_rev_map_filter: ('a -> 'b option) -> 'a list -> 'b list
 val list_rev_map_filter_fold: ('c -> 'a -> 'c * 'b option) -> 'c -> 'a list -> 'c * 'b list