Add mapSelected and indexedMapSelected

src/Array/NonEmpty.elm

@@ -12,9 +12,11 @@ module Array.NonEmpty
         , getFirst
         , getSelected
         , indexedMap
+        , indexedMapSelected
         , initialize
         , length
         , map
+        , mapSelected
         , push
         , removeAt
         , removeAtSafe
@@ -62,7 +64,7 @@ Most functions (like `map`) keep the currently selected index untouched, other f
 
 # Selected Index
 
-@docs selectedIndex, setSelectedIndex, setSelectedIndexAndReport, getSelected, updateSelected
+@docs selectedIndex, setSelectedIndex, setSelectedIndexAndReport, getSelected, updateSelected, mapSelected, indexedMapSelected
 
 
 # Conversions
@@ -568,6 +570,52 @@ indexedMap function (NEA first selected rest) =
     NEA newFirst selected newRest
 
 
+{-| Apply different functions to every element in an array depending on whether
+the element is selected or not.
+
+    Just <|
+      (repeat 5 1
+        |> mapSelected (\isSelected ->
+          if isSelected then
+            (*) 2
+          else
+            Basics.identity
+        ))
+      --> fromList [2, 1, 1, 1, 1]
+
+-}
+mapSelected : (Bool -> a -> b) -> NonEmptyArray a -> NonEmptyArray b
+mapSelected function array =
+    let
+        innerFn index =
+            function (index == selectedIndex array)
+    in
+    indexedMap innerFn array
+
+
+{-| Apply different functions to every element with its index as first argument
+depending on whether the element is selected or not.
+
+    Just <|
+      (repeat 5 1
+        |> indexedMapSelected (\isSelected ->
+          if isSelected then
+            (*)
+          else
+            (+)
+        ))
+      --> fromList [0, 2, 3, 4, 5]
+
+-}
+indexedMapSelected : (Bool -> Int -> a -> b) -> NonEmptyArray a -> NonEmptyArray b
+indexedMapSelected function array =
+    let
+        innerFn index =
+            function (index == selectedIndex array) index
+    in
+    indexedMap innerFn array
+
+
 {-| Append two arrays to a new one.
 
     Just (append (repeat 2 42) (repeat 3 81)) --> fromList [42, 42, 81, 81, 81]

tests/NonEmptyArrayTest.elm

@@ -4,7 +4,6 @@ import Array.Hamt as Array exposing (Array)
 import Array.NonEmpty as NEA exposing (NonEmptyArray)
 import Expect exposing (Expectation)
 import Fuzz exposing (Fuzzer)
-import Random
 import Test exposing (..)
 
 
@@ -908,6 +907,51 @@ suite =
                         , Expect.equal Nothing (NEA.get 3 nea)
                         ]
             ]
+        , describe "mapSelected"
+            [ test "mapping over a single element" <|
+                \_ ->
+                    let
+                        nea =
+                            NEA.fromElement 1
+                                |> NEA.mapSelected addFiveOrMultiplyTwo
+                    in
+                    Expect.equal 6 (NEA.getFirst nea)
+            , test "mapping over multiple elements" <|
+                \_ ->
+                    let
+                        mnea =
+                            NEA.fromList [ 1, 2, 3, 4 ]
+                                |> Maybe.map (NEA.mapSelected addFiveOrMultiplyTwo)
+                    in
+                    expectMaybe
+                        (\nea ->
+                            expectAll
+                                [ Expect.equal 4 (NEA.length nea)
+                                , Expect.equal (Just 6) (NEA.get 0 nea)
+                                , Expect.equal (Just 4) (NEA.get 1 nea)
+                                , Expect.equal (Just 6) (NEA.get 2 nea)
+                                , Expect.equal (Just 8) (NEA.get 3 nea)
+                                , Expect.equal Nothing (NEA.get 4 nea)
+                                ]
+                        )
+                        mnea
+            ]
+        , describe "indexedMapSelected"
+            [ test "indexedMapSelected over multiple elements" <|
+                \_ ->
+                    let
+                        nea =
+                            NEA.initialize 3 identity
+                                |> NEA.indexedMapSelected multiplyOrAdd
+                    in
+                    expectAll
+                        [ Expect.equal 3 (NEA.length nea)
+                        , Expect.equal (Just 0) (NEA.get 0 nea)
+                        , Expect.equal (Just 2) (NEA.get 1 nea)
+                        , Expect.equal (Just 4) (NEA.get 2 nea)
+                        , Expect.equal Nothing (NEA.get 3 nea)
+                        ]
+            ]
         , describe "filter"
             [ test "filter to zero elements returns Nothing" <|
                 \_ ->
@@ -1353,6 +1397,14 @@ suite =
         ]
 
 
+addFiveOrMultiplyTwo : Bool -> Int -> Int
+addFiveOrMultiplyTwo isSelected =
+    if isSelected then
+        (+) 5
+    else
+        (*) 2
+
+
 expectJust : Maybe (NonEmptyArray a) -> Expectation
 expectJust maybe =
     case maybe of
@@ -1399,6 +1451,14 @@ intList =
     Fuzz.list (Fuzz.intRange 0 1000)
 
 
+multiplyOrAdd : Bool -> Int -> Int -> Int
+multiplyOrAdd isSelected =
+    if isSelected then
+        (*)
+    else
+        (+)
+
+
 nonEmptyIntList : Fuzzer (List Int)
 nonEmptyIntList =
     intList