Adds a directory for shared code.

1 files changed, 36 insertions, 0 deletions

diff --git a/src/shared/elm/Util/List.elm b/src/shared/elm/Util/List.elm
new file mode 100644
index 0000000..1f914b1
--- /dev/null
+++ b/src/shared/elm/Util/List.elm
@@ -0,0 +1,36 @@
+module Util.List exposing (..)
+
+import List
+
+pop : List a -> (Maybe (a, List a))
+pop l =
+   case
+      ((List.head l), (List.tail l))
+   of
+      (Nothing, _) -> Nothing
+      (_ , Nothing) -> Nothing
+      ((Just head), (Just tail)) -> (Just (head, tail))
+
+get_first : (a -> Bool) -> (List a) -> (Maybe a)
+get_first fun list =
+   (List.head (List.filter fun list))
+
+product_map : (a -> b -> c) -> (List a) -> (List b) -> (List c)
+product_map product_fun list_a list_b =
+   (product_map_rec (product_fun) list_a list_b [])
+
+product_map_rec : (a -> b -> c) -> (List a) -> (List b) -> (List c) -> (List c)
+product_map_rec product_fun list_a list_b result =
+   case (pop list_a) of
+      Nothing -> result
+      (Just (head, tail)) ->
+         (product_map_rec
+            (product_fun)
+            tail
+            list_b
+            (List.append
+               (List.map (product_fun head) list_b)
+               result
+            )
+         )
+