464c4e8 · elk · git.iko.soy

git.iko.soy/elk

Merge pull request #300 from erdeszt/list-init

Add init function

commit464c4e82560f050bf4cb4edbf02fc35d9b670845 authorEvan Czaplicki <info@elm-lang.org> dateFri 18 Oct 2013, 09:08 (13 years ago) parent83406ff 2ffacb7

2 files changed+21−1

compare with master

unifiedsplit

libraries/List.elm+7−1 libraries/Native/List.js+14

libraries/List.elm+7−1

@@ -7,7 +7,7 @@ list must have the same type.

77@docs (::), (++), isEmpty, length, reverse, map

99# Sub-lists

10−@docs head, tail, last, filter, take, drop

10+@docs head, tail, last, init, filter, take, drop

1111

1212# Putting Lists Together

1313@docs concat, concatMap, join, intersperse, zip, zipWith

@@ -58,6 +58,12 @@ tail = Native.List.tail

5858last : [a] -> a

5959last = Native.List.last

6060

61+{-| Extract the elements before the last element in the list. List must be non-empty.

62+`(init [1,2,3] == [1,2])

63+-}

64+init : [a] -> [a]

65+init = Native.List.init

66+

6167{-| Check if a list is empty `(isEmpty [] == True)` -}

6268isEmpty : [a] -> Bool

6369isEmpty xs =

libraries/Native/List.js+14

@@ -81,6 +81,19 @@ Elm.Native.List.make = function(elm) {

8181 return out;

8282 }

8383

84+ function init(xs) {

85+ if (xs.ctor === '[]') { throwError('init'); }

86+ var root = Cons(xs._0, Nil);

87+ var curr = root;

88+ xs = xs._1;

89+ while (xs._1.ctor !== '[]') {

90+ curr._1 = Cons(xs._0, Nil)

91+ xs = xs._1

92+ curr = curr._1

93+ }

94+ return root;

95+ }

96+

8497 function map(f, xs) {

8598 var arr = [];

8699 while (xs.ctor !== '[]') {

@@ -278,6 +291,7 @@ Elm.Native.List.make = function(elm) {

278291 head:head,

279292 tail:tail,

280293 last:last,

294+ init:init,

281295

282296 map:F2(map),

283297 foldl:F3(foldl),