add infix operator (=|>) to compose Optional with Lens

README.md

@@ -262,6 +262,11 @@ Allows to chain lens composition for deeply nested structures:
  .getOption (maybe => array 2) (Just <| Array.fromList [ 10, 11, 12, 13 ])
  > 12
 ```
+#### Convenient infix operator for composing optional with lens.
+```elm
+ .getOption (maybe =|> id) (Just { id = 12 })
+ > 12
+```
 #### Step into a `Maybe` value.
 ```elm 
  maybe.set 5 Nothing

elm-package.json

@@ -1,5 +1,5 @@
 {
- "version": "1.5.1",
+ "version": "1.6.0",
  "summary": "Library providing functional tools to manipulate complex records",
  "repository": "https://github.com/arturopala/elm-monocle.git",
  "license": "MIT",

package.json

@@ -1,6 +1,6 @@
 {
  "name": "elm-monocle",
- "version": "1.5.2",
+ "version": "1.6.0",
  "description": "Library providing purely functional abstractions to manipulate records",
  "scripts": {
  "compile": "elm-make ./src/**/*.elm --output monocle.js",

src/Monocle/Common.elm

@@ -4,13 +4,15 @@ module Monocle.Common exposing (..)
 
 @docs (<|>)
 @docs (=>)
+@docs (=|>)
 @docs maybe
 @docs array
 @docs dict
 @docs result
 @docs id
 @docs first
 @docs second
+
 -}
 
 import Array exposing (Array)
@@ -20,7 +22,7 @@ import Monocle.Optional as Optional exposing (Optional)
 
 
 {-| Convenient Infix operator for composing lenses.
- Allows to chain lens composition for deeply nested structures:
+Allows to chain lens composition for deeply nested structures:
 
  fromAtoB : Lens A B
  fromAtoB = Lense .b (\a b -> { a | b = b })
@@ -45,6 +47,7 @@ import Monocle.Optional as Optional exposing (Optional)
 
  fromAtoE.set a "What we want to set"
  => { b: { c: { d: { e: "What we want to set" } } } }
+
 -}
 (<|>) : Lens a b -> Lens b c -> Lens a c
 (<|>) =
@@ -53,19 +56,33 @@ import Monocle.Optional as Optional exposing (Optional)
 
 {-| Convenient infix operator for composing optionals.
 
- .getOption (maybe => array 2) (Just <| Array.fromList [ 10, 11, 12, 13 ])
- > 12
+.getOption (maybe => array 2) (Just <| Array.fromList [ 10, 11, 12, 13 ])
+
+> 12
 
 -}
 (=>) : Optional a b -> Optional b c -> Optional a c
 (=>) =
  Optional.compose
 
 
+{-| Convenient infix operator for composing optional with lens.
+
+.getOption (maybe =|> id) (Just { id = 12 })
+
+> 12
+
+-}
+(=|>) : Optional a b -> Lens b c -> Optional a c
+(=|>) a b =
+ Optional.compose a (Optional.fromLens b)
+
+
 {-| Step into a `Maybe` value.
 
  maybe.set 5 Nothing
  > Just 5
+
 -}
 maybe : Optional (Maybe a) a
 maybe =
@@ -81,6 +98,7 @@ maybe =
 
  .getOption (array 8) (Array.fromList [ 10, 11, 12, 13 ])
  > Nothing
+
 -}
 array : Int -> Optional (Array a) a
 array index =
@@ -96,6 +114,7 @@ array index =
 
  .getOption (dict "Jerry") (Dict.fromList [ ( "Tom", "Cat" ) ])
  > Nothing
+
 -}
 dict : comparable -> Optional (Dict comparable v) v
 dict key =
@@ -111,6 +130,7 @@ dict key =
 
  result.getOption (Err "500")
  > Nothing
+
 -}
 result : Optional (Result e a) a
 result =
@@ -127,6 +147,7 @@ result =
 Since records with an `id` field are incredible common, this is
 included for convenience. It also serves as a simple recipe for
 creating record lenses.
+
 -}
 id : Lens { a | id : b } b
 id =
@@ -139,6 +160,7 @@ id =
 
  first.get ( 'a', 'b' )
  > Just 'a'
+
 -}
 first : Lens ( a, b ) a
 first =
@@ -151,6 +173,7 @@ first =
 
  second.get ( 'a', 'b' )
  > Just 'b'
+
 -}
 second : Lens ( a, b ) b
 second =

tests/CommonSpec.elm

@@ -6,17 +6,50 @@ import Fuzz exposing (list, int, tuple, string, char)
 import String
 import Dict
 import Maybe
-import Monocle.Common exposing (dict)
+import Array
+import Monocle.Common exposing (dict, (=>), (=|>), maybe, array, id)
 
 
 all : Test
 all =
  describe "A Common specification"
- [ test_dict_empty
+ [ test_maybe
+ , test_array_just
+ , test_array_nothing
+ , test_dict_empty
  , test_dict_list
+ , test_infix_compose_optionals
+ , test_infix_compose_optional_with_lens
  ]
 
 
+test_maybe : Test
+test_maybe =
+ let
+ test s =
+ maybe.set s Nothing |> Expect.equal (Just s)
+ in
+ fuzz string "Common.maybe should step into Maybe" test
+
+
+test_array_just : Test
+test_array_just =
+ let
+ test i =
+ .getOption (array 2) (Array.fromList [ 10, 11, i, 13 ]) |> Expect.equal (Just i)
+ in
+ fuzz int "Common.array should get some value at position 2" test
+
+
+test_array_nothing : Test
+test_array_nothing =
+ let
+ test i =
+ .getOption (array 8) (Array.fromList [ i, i, i, i, i, i, i, i ]) |> Expect.equal Nothing
+ in
+ fuzz int "Common.array should return nothing if index out of bound" test
+
+
 test_dict_empty : Test
 test_dict_empty =
  let
@@ -39,3 +72,21 @@ test_dict_list =
  .getOption opt (Dict.fromList [ ( "Tom", s ), ( "Alice", "Rabbit" ) ]) |> Expect.equal (Just s)
  in
  fuzz string "Common.dict should set and get value by key (preloaded dict)" test
+
+
+test_infix_compose_optionals : Test
+test_infix_compose_optionals =
+ let
+ test i =
+ .getOption (maybe => array 2) (Just <| Array.fromList [ 10, 11, i, 13 ]) |> Expect.equal (Just i)
+ in
+ fuzz int "Common.=> should compose 2 Optionals" test
+
+
+test_infix_compose_optional_with_lens : Test
+test_infix_compose_optional_with_lens =
+ let
+ test i =
+ .getOption (maybe =|> id) (Just { id = i }) |> Expect.equal (Just i)
+ in
+ fuzz int "Common.=|> should compose Optional with Lens" test