1 files changed, 47 insertions, 0 deletions
diff --git a/website/sandbox/learnpianochords/src/Misc.elm b/website/sandbox/learnpianochords/src/Misc.elm
new file mode 100644
index 000000000000..52f957ad528f
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+++ b/website/sandbox/learnpianochords/src/Misc.elm
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+module Misc exposing (..)
+
+import Array exposing (Array)
+
+
+comesAfter : a -> List a -> Maybe a
+comesAfter x xs =
+    case xs of
+        [] ->
+            Nothing
+
+        _ :: [] ->
+            Nothing
+
+        y :: z :: rest ->
+            if y == x then
+                Just z
+
+            else
+                comesAfter x (z :: rest)
+
+
+comesBefore : a -> List a -> Maybe a
+comesBefore x xs =
+    case xs of
+        [] ->
+            Nothing
+
+        _ :: [] ->
+            Nothing
+
+        y :: z :: rest ->
+            if z == x then
+                Just y
+
+            else
+                comesBefore x (z :: rest)
+
+
+find : (a -> Bool) -> List a -> Maybe a
+find pred xs =
+    case xs |> List.filter pred of
+        [] ->
+            Nothing
+
+        x :: _ ->
+            Just x