f636b75 · elk · git.iko.soy

git.iko.soy/elk

Merge pull request #409 from maxsnew/keepWhen

Change semantics of keepWhen/dropWhen.

commitf636b7576f3856ee6105668af0449297cee1fc0e authorEvan Czaplicki <info@elm-lang.org> dateTue 28 Jan 2014, 06:18 (13 years ago) parent56c4fb9 50bc5a4

2 files changed+7−11

compare with master

unifiedsplit

libraries/Native/Signal/Signal.js−9 libraries/Signal.elm+7−2

libraries/Native/Signal/Signal.js−9

@@ -127,12 +127,6 @@ Elm.Native.Signal.make = function(elm) {

127127 input.kids.push(this);

128128 }

129129

130− function dropWhen(s1,b,s2) {

131− var pairs = lift2( F2(function(x,y){return {x:x,y:y};}), s1, s2 );

132− var dropped = new DropIf(function(p){return p.x;},{x:true,y:b},pairs);

133− return lift(function(p){return p.y;}, dropped);

134− }

135−

136130 function timestamp(a) {

137131 function update() { return Utils.Tuple2(Date.now(), a.value); }

138132 return new LiftN(update, [a]);

@@ -225,9 +219,6 @@ Elm.Native.Signal.make = function(elm) {

225219 keepIf : F3(function(pred,base,sig) {

226220 return new DropIf(function(x) {return !pred(x);},base,sig); }),

227221 dropIf : F3(function(pred,base,sig) { return new DropIf(pred,base,sig); }),

228− keepWhen : F3(function(s1,b,s2) {

229− return dropWhen(lift(function(b){return !b;},s1), b, s2); }),

230− dropWhen : F3(dropWhen),

231222 dropRepeats : function(s) { return new DropRepeats(s);},

232223 sampleOn : F2(sampleOn),

233224 timestamp : timestamp

libraries/Signal.elm+7−2

@@ -32,6 +32,10 @@ the [`Time`](/docs/Signal/Time.elm) library.

3232import Native.Signal

3333import List (foldr)

3434

35+import Basics (fst, snd, not)

36+import Native.Error

37+import Maybe as M

38+

3539data Signal a = Signal

3640

3741{-| Create a constant signal that never changes. -}

@@ -122,7 +126,8 @@ Until the first signal becomes false again, all events will be propagated. Elm

122126does not allow undefined signals, so a base case must be provided in case the

123127first signal is not true initially. -}

124128keepWhen : Signal Bool -> a -> Signal a -> Signal a

125−keepWhen = Native.Signal.keepWhen

129+keepWhen bs def sig =

130+ snd <~ (keepIf fst (False, def) ((,) <~ (sampleOn sig bs) ~ sig))

126131

127132{-| Drop events when the first signal is true. When the first signal becomes

128133false, the most recent value of the second signal will be propagated. Until the

@@ -130,7 +135,7 @@ first signal becomes true again, all events will be propagated. Elm does not

130135allow undefined signals, s oa base case must be provided in case the first

131136signal is true initially. -}

132137dropWhen : Signal Bool -> a -> Signal a -> Signal a

133−dropWhen = Native.Signal.dropWhen

138+dropWhen bs = keepWhen (not <~ bs)

134139

135140{-| Drop updates that repeat the current value of the signal.

136141