Steal a `concat_map` implementation from Karuta

2 files changed, 5 insertions, 0 deletions

diff --git a/lib/Utilities.ml b/lib/Utilities.ml
index 8b6b08e..dcf4417 100644
--- a/lib/Utilities.ml
+++ b/lib/Utilities.ml
@@ -92,6 +92,10 @@ module FingerTree = struct
       (fun acc elem ->
         match f elem with None -> acc | Some result -> BatFingerTree.snoc acc result)
       BatFingerTree.empty
+
+  let concat_map f =
+    BatFingerTree.fold_left (fun acc elem -> BatFingerTree.append acc @@ f elem) BatFingerTree.empty
+
 end
 
 module Atomic = struct
diff --git a/lib/Utilities.mli b/lib/Utilities.mli
index f220b08..7d41e20 100644
--- a/lib/Utilities.mli
+++ b/lib/Utilities.mli
@@ -36,6 +36,7 @@ module FingerTree : sig
   val foldm_left : ('a -> 'b -> ('a, 'e) result) -> 'a -> 'b BatFingerTree.t -> ('a, 'e) result
   val join : string BatFingerTree.t -> string -> string
   val filter_map : ('a -> 'b option) -> 'a BatFingerTree.t -> 'b BatFingerTree.t
+  val concat_map : ('a -> ('b BatFingerTree.t, 'e) result) -> 'a BatFingerTree.t -> ('b BatFingerTree.t, 'e) result
 end
 
 module Fun : sig