8a89c86 · elk · git.iko.soy

git.iko.soy/elk

Shuffle the optimized AST to make code gen easier

For example, each case expression saves a temporary variable just in case. That means we do all variable name generation in the optimize phase, so the generate phase can be pure function from Elm to JS AST.

commit8a89c868b2d6a4b916e60c7307d2d84e3a26c1f2 authorEvan Czaplicki <evancz@users.noreply.github.com> dateTue 5 Dec 2017, 14:34 (9 years ago) parent022925a

6 files changed+116−131

compare with master

unifiedsplit

src/AST/Optimized.hs+25−27 src/Optimize/Case.hs+11−25 src/Optimize/DecisionTree.hs+20−19 src/Optimize/Expression.hs+40−31 src/Optimize/Module.hs+6−15 src/Optimize/Port.hs+14−14

src/AST/Optimized.hs+25−27

@@ -39,17 +39,16 @@ data Expr

3939 | VarLocal N.Name

4040 | VarGlobal Global

4141 | VarCycle ModuleName.Canonical N.Name

42− | VarDebug N.Name ModuleName.Canonical R.Region (Maybe Expr)

42+ | VarDebug N.Name ModuleName.Canonical R.Region (Maybe N.Name)

4343 | VarKernel N.Name N.Name

4444 | List [Expr]

4545 | Function [N.Name] Expr

4646 | Call Expr [Expr]

47− | TailCall N.Name [N.Name] [Expr]

47+ | TailCall N.Name [(N.Name, Expr)]

4848 | If [(Expr, Expr)] Expr

4949 | Let Def Expr

50− | Case N.Name (Decider Choice) [(Int, Expr)]

51− | Ctor N.Name [Expr]

52− | CtorAccess Expr Index.ZeroBased

50+ | Case N.Name N.Name (Decider Choice) [(Int, Expr)]

51+ | Index Expr Int

5352 | Accessor N.Name

5453 | Access Expr N.Name

5554 | Update Expr (Map.Map N.Name Expr)

@@ -116,6 +115,7 @@ data Main

116115data Node

117116 = Define Expr (Set.Set N.Name) (Set.Set Global)

118117 | DefineTailFunc [N.Name] Expr (Set.Set N.Name) (Set.Set Global)

118+ | Ctor N.Name Index.ZeroBased Int

119119 | Link Global

120120 | Cycle [(N.Name, Expr)] (Set.Set N.Name) (Set.Set Global)

121121 | PortIncoming Expr (Set.Set N.Name) (Set.Set Global)

@@ -150,19 +150,18 @@ instance Binary Expr where

150150 List a -> putWord8 9 >> put a

151151 Function a b -> putWord8 10 >> put a >> put b

152152 Call a b -> putWord8 11 >> put a >> put b

153− TailCall a b c -> putWord8 12 >> put a >> put b >> put c

153+ TailCall a b -> putWord8 12 >> put a >> put b

154154 If a b -> putWord8 13 >> put a >> put b

155155 Let a b -> putWord8 14 >> put a >> put b

156− Case a b c -> putWord8 15 >> put a >> put b >> put c

157− Ctor a b -> putWord8 16 >> put a >> put b

158− CtorAccess a b -> putWord8 17 >> put a >> put b

159− Accessor a -> putWord8 18 >> put a

160− Access a b -> putWord8 19 >> put a >> put b

161− Update a b -> putWord8 20 >> put a >> put b

162− Record a -> putWord8 21 >> put a

163− Unit -> putWord8 22

164− Tuple a b c -> putWord8 23 >> put a >> put b >> put c

165− Shader a -> putWord8 24 >> put a

156+ Case a b c d -> putWord8 15 >> put a >> put b >> put c >> put d

157+ Index a b -> putWord8 16 >> put a >> put b

158+ Accessor a -> putWord8 17 >> put a

159+ Access a b -> putWord8 18 >> put a >> put b

160+ Update a b -> putWord8 19 >> put a >> put b

161+ Record a -> putWord8 20 >> put a

162+ Unit -> putWord8 21

163+ Tuple a b c -> putWord8 22 >> put a >> put b >> put c

164+ Shader a -> putWord8 23 >> put a

166165

167166 get =

168167 do word <- getWord8

@@ -179,19 +178,18 @@ instance Binary Expr where

179178 9 -> liftM List get

180179 10 -> liftM2 Function get get

181180 11 -> liftM2 Call get get

182− 12 -> liftM3 TailCall get get get

181+ 12 -> liftM2 TailCall get get

183182 13 -> liftM2 If get get

184183 14 -> liftM2 Let get get

185− 15 -> liftM3 Case get get get

186− 16 -> liftM2 Ctor get get

187− 17 -> liftM2 CtorAccess get get

188− 18 -> liftM Accessor get

189− 19 -> liftM2 Access get get

190− 20 -> liftM2 Update get get

191− 21 -> liftM Record get

192− 22 -> pure Unit

193− 23 -> liftM3 Tuple get get get

194− 24 -> liftM Shader get

184+ 15 -> liftM4 Case get get get get

185+ 16 -> liftM2 Index get get

186+ 17 -> liftM Accessor get

187+ 18 -> liftM2 Access get get

188+ 19 -> liftM2 Update get get

189+ 20 -> liftM Record get

190+ 21 -> pure Unit

191+ 22 -> liftM3 Tuple get get get

192+ 23 -> liftM Shader get

195193 _ -> error "problem getting Opt.Expr binary"

196194

197195

src/Optimize/Case.hs+11−25

@@ -20,13 +20,21 @@ import qualified Optimize.DecisionTree as DT

2020-- OPTIMIZE A CASE EXPRESSION

2121

2222

23−optimize :: N.Name -> [(Can.Pattern, Opt.Expr)] -> Opt.Expr

24−optimize exprName optBranches =

23+optimize :: N.Name -> N.Name -> [(Can.Pattern, Opt.Expr)] -> Opt.Expr

24+optimize temp root optBranches =

2525 let

2626 (patterns, indexedBranches) =

2727 unzip (zipWith indexify [0..] optBranches)

28+

29+ decider = treeToDecider (DT.compile patterns)

30+ targetCounts = countTargets decider

31+

32+ (choices, maybeJumps) =

33+ unzip (map (createChoices targetCounts) indexedBranches)

2834 in

29− treeToExpr exprName (DT.compile patterns) indexedBranches

35+ Opt.Case temp root

36+ (insertChoices (Map.fromList choices) decider)

37+ (Maybe.catMaybes maybeJumps)

3038

3139

3240indexify :: Int -> (a,b) -> ((a,Int), (Int,b))

@@ -37,28 +45,6 @@ indexify index (pattern, branch) =

3745

3846

3947

40−-- CONVERT A TREE TO AN EXPRESSION

41−

42−

43−treeToExpr :: N.Name -> DT.DecisionTree -> [(Int, Opt.Expr)] -> Opt.Expr

44−treeToExpr name decisionTree allJumps =

45− let

46− decider =

47− treeToDecider decisionTree

48−

49− targetCounts =

50− countTargets decider

51−

52− (choices, maybeJumps) =

53− unzip (map (createChoices targetCounts) allJumps)

54− in

55− Opt.Case

56− name

57− (insertChoices (Map.fromList choices) decider)

58− (Maybe.catMaybes maybeJumps)

59−

60−

61−

6248-- TREE TO DECIDER

6349--

6450-- Decision trees may have some redundancies, so we convert them to a Decider

src/Optimize/DecisionTree.hs+20−19

@@ -21,7 +21,7 @@ as SML/NJ to get nice trees.

2121-}

2222

2323import Control.Arrow (second)

24−import Control.Monad (liftM, liftM2)

24+import Control.Monad (liftM, liftM2, liftM3)

2525import Data.Binary

2626import qualified Data.List as List

2727import qualified Data.Maybe as Maybe

@@ -29,6 +29,7 @@ import qualified Data.Set as Set

2929import Data.Text (Text)

3030

3131import qualified AST.Canonical as Can

32+import qualified Data.Index as Index

3233import qualified Elm.Name as N

3334import qualified Reporting.Annotation as A

3435

@@ -70,7 +71,7 @@ data DecisionTree

7071

7172

7273data Test

73− = IsCtor Int N.Name

74+ = IsCtor Int N.Name Index.ZeroBased

7475 | IsInt Int

7576 | IsChr Text

7677 | IsStr Text

@@ -162,7 +163,7 @@ toDecisionTree rawBranches =

162163isComplete :: [Test] -> Bool

163164isComplete tests =

164165 case head tests of

165− IsCtor alts _ ->

166+ IsCtor alts _ _ ->

166167 alts == length tests

167168

168169 _ ->

@@ -207,7 +208,7 @@ flatten pathPattern@(path, A.At region pattern) =

207208 Can.PTuple a b (Just c) ->

208209 concatMap flatten (subPositions path [a,b,c])

209210

210− Can.PCtor _ _ _ (Can.CtorAlts numAlts _) _ args ->

211+ Can.PCtor _ _ _ (Can.CtorAlts numAlts _) _ _ args ->

211212 if numAlts == 1 then

212213 concatMap flatten (subPositions path (map dearg args))

213214 else

@@ -304,8 +305,8 @@ testAtPath selectedPath (Branch _ pathPatterns) =

304305

305306 Just (A.At _ pattern) ->

306307 case pattern of

307− Can.PCtor _ _ _ (Can.CtorAlts numAlts _) name _ ->

308− Just (IsCtor numAlts name)

308+ Can.PCtor _ _ _ (Can.CtorAlts numAlts _) name index _ ->

309+ Just (IsCtor numAlts name index)

309310

310311 Can.PInt int ->

311312 Just (IsInt int)

@@ -346,12 +347,12 @@ testAtPath selectedPath (Branch _ pathPatterns) =

346347

347348{-# NOINLINE nilTest #-}

348349nilTest :: Test

349−nilTest = IsCtor 2 "[]"

350+nilTest = IsCtor 2 "[]" (Index.unsafe (-1))

350351

351352

352353{-# NOINLINE consTest #-}

353354consTest :: Test

354−consTest = IsCtor 2 "::"

355+consTest = IsCtor 2 "::" (Index.unsafe (-2))

355356

356357

357358

@@ -370,27 +371,27 @@ toRelevantBranch test path branch@(Branch goal pathPatterns) =

370371 case extract path pathPatterns of

371372 Just (start, A.At region pattern, end) ->

372373 case pattern of

373− Can.PCtor _ _ _ (Can.CtorAlts numAlts _) name args ->

374− if test == IsCtor numAlts name then

374+ Can.PCtor _ _ _ (Can.CtorAlts numAlts _) name index args ->

375+ if test == IsCtor numAlts name index then

375376 Just (Branch goal (start ++ subPositions path (map dearg args) ++ end))

376377 else

377378 Nothing

378379

379380 Can.PList [] ->

380− if test == IsCtor 2 "[]" then

381+ if test == nilTest then

381382 Just (Branch goal (start ++ end))

382383 else

383384 Nothing

384385

385386 Can.PList (hd:tl) ->

386− if test == IsCtor 2 "::" then

387+ if test == consTest then

387388 let tl' = A.At region (Can.PList tl) in

388389 Just (Branch goal (start ++ subPositions path [ hd, tl' ] ++ end))

389390 else

390391 Nothing

391392

392393 Can.PCons hd tl ->

393− if test == IsCtor 2 "::" then

394+ if test == consTest then

394395 Just (Branch goal (start ++ subPositions path [hd,tl] ++ end))

395396 else

396397 Nothing

@@ -471,7 +472,7 @@ needsTests (A.At _ pattern) =

471472 Can.PRecord _ ->

472473 False

473474

474− Can.PCtor _ _ _ _ _ _ ->

475+ Can.PCtor _ _ _ _ _ _ _ ->

475476 True

476477

477478 Can.PList _ ->

@@ -573,15 +574,15 @@ smallBranchingFactor branches path =

573574instance Binary Test where

574575 put test =

575576 case test of

576− IsCtor a b -> putWord8 0 >> put a >> put b

577− IsChr a -> putWord8 1 >> put a

578− IsStr a -> putWord8 2 >> put a

579− IsInt a -> putWord8 3 >> put a

577+ IsCtor a b c -> putWord8 0 >> put a >> put b >> put c

578+ IsChr a -> putWord8 1 >> put a

579+ IsStr a -> putWord8 2 >> put a

580+ IsInt a -> putWord8 3 >> put a

580581

581582 get =

582583 do word <- getWord8

583584 case word of

584− 0 -> liftM2 IsCtor get get

585+ 0 -> liftM3 IsCtor get get get

585586 1 -> liftM IsChr get

586587 2 -> liftM IsStr get

587588 3 -> liftM IsInt get

src/Optimize/Expression.hs+40−31

@@ -130,14 +130,14 @@ optimize cycle (A.At region expression) =

130130 obranch <- optimize cycle branch

131131 pure (pattern, foldr Opt.Let obranch defs)

132132 in

133− do oexpr <- optimize cycle expr

133+ do temp <- Names.generate

134+ oexpr <- optimize cycle expr

134135 case oexpr of

135136 Opt.VarLocal root ->

136− Case.optimize root <$> traverse (optimizeBranch root) branches

137+ Case.optimize temp root <$> traverse (optimizeBranch root) branches

137138

138139 _ ->

139− do root <- Names.generate

140− Case.optimize root <$> traverse (optimizeBranch root) branches

140+ Case.optimize temp temp <$> traverse (optimizeBranch temp) branches

141141

142142 Can.Accessor field ->

143143 Names.registerField field (Opt.Accessor field)

@@ -246,13 +246,13 @@ destructHelp root (A.At region pattern) revDefs =

246246 let newRevDefs = Opt.Def name root : revDefs

247247 case maybeC of

248248 Nothing ->

249− destructHelp (Opt.CtorAccess tuple Index.second) b =<<

250− destructHelp (Opt.CtorAccess tuple Index.first) a newRevDefs

249+ destructHelp (Opt.Index tuple 1) b =<<

250+ destructHelp (Opt.Index tuple 0) a newRevDefs

251251

252252 Just c ->

253− destructHelp (Opt.CtorAccess tuple Index.third) c =<<

254− destructHelp (Opt.CtorAccess tuple Index.second) b =<<

255− destructHelp (Opt.CtorAccess tuple Index.first) a newRevDefs

253+ destructHelp (Opt.Index tuple 2) c =<<

254+ destructHelp (Opt.Index tuple 1) b =<<

255+ destructHelp (Opt.Index tuple 0) a newRevDefs

256256

257257 Can.PList [] ->

258258 pure revDefs

@@ -272,7 +272,7 @@ destructHelp root (A.At region pattern) revDefs =

272272 Can.PInt _ ->

273273 pure revDefs

274274

275− Can.PCtor _ _ _ _ _ args ->

275+ Can.PCtor _ _ _ _ _ _ args ->

276276 do name <- Names.generate

277277 foldM

278278 (destructCtorArg (Opt.VarLocal name))

@@ -284,13 +284,13 @@ destructCons :: Opt.Expr -> Can.Pattern -> Can.Pattern -> [Opt.Def] -> Names.Tra

284284destructCons root hd tl revDefs =

285285 do name <- Names.generate

286286 let list = Opt.VarLocal name

287− destructHelp (Opt.CtorAccess list Index.first) hd =<<

288− destructHelp (Opt.CtorAccess list Index.second) tl (Opt.Def name root : revDefs)

287+ destructHelp (Opt.Index list 0) hd =<<

288+ destructHelp (Opt.Index list 1) tl (Opt.Def name root : revDefs)

289289

290290

291291destructCtorArg :: Opt.Expr -> [Opt.Def] -> Can.PatternCtorArg -> Names.Tracker [Opt.Def]

292292destructCtorArg root revDefs (Can.PatternCtorArg index _ arg) =

293− destructHelp (Opt.CtorAccess root index) arg revDefs

293+ destructHelp (Opt.Index root (Index.toZeroBased index)) arg revDefs

294294

295295

296296

@@ -312,37 +312,46 @@ optimizePotentialTailCall cycle def =

312312

313313

314314optimizeTail :: Cycle -> N.Name -> [N.Name] -> Can.Expr -> Names.Tracker Opt.Expr

315−optimizeTail cycle name argNames locExpr@(A.At _ expression) =

315+optimizeTail cycle rootName argNames locExpr@(A.At _ expression) =

316316 case expression of

317− Can.Call (A.At _ (Can.VarTopLevel _ funcName)) args ->

318− if funcName == name && length args == length argNames then

319− Opt.TailCall name argNames <$> traverse (optimize cycle) args

320− else

321− optimize cycle locExpr

317+ Can.Call func@(A.At _ (Can.VarTopLevel _ name)) args ->

318+ do oargs <- traverse (optimize cycle) args

319+ if name == rootName

320+ then

321+ case Index.indexedZipWith (\_ a b -> (a,b)) argNames oargs of

322+ Index.LengthMatch pairs ->

323+ pure $ Opt.TailCall name pairs

324+

325+ Index.LengthMismatch _ _ ->

326+ do ofunc <- optimize cycle func

327+ pure $ Opt.Call ofunc oargs

328+ else

329+ do ofunc <- optimize cycle func

330+ pure $ Opt.Call ofunc oargs

322331

323332 Can.If branches finally ->

324333 let

325334 optimizeBranch (condition, branch) =

326335 (,)

327336 <$> optimize cycle condition

328− <*> optimizeTail cycle name argNames branch

337+ <*> optimizeTail cycle rootName argNames branch

329338 in

330339 Opt.If

331340 <$> traverse optimizeBranch branches

332− <*> optimizeTail cycle name argNames finally

341+ <*> optimizeTail cycle rootName argNames finally

333342

334343 Can.Let def body ->

335− optimizeDef cycle def =<< optimizeTail cycle name argNames body

344+ optimizeDef cycle def =<< optimizeTail cycle rootName argNames body

336345

337346 Can.LetRec defs body ->

338347 case defs of

339348 [def] ->

340349 Opt.Let

341350 <$> optimizePotentialTailCall cycle def

342− <*> optimizeTail cycle name argNames body

351+ <*> optimizeTail cycle rootName argNames body

343352

344353 _ ->

345− do obody <- optimizeTail cycle name argNames body

354+ do obody <- optimizeTail cycle rootName argNames body

346355 foldM (\bod def -> optimizeDef cycle def bod) obody defs

347356

348357 Can.LetDestruct pattern expr body ->

@@ -356,17 +365,17 @@ optimizeTail cycle name argNames locExpr@(A.At _ expression) =

356365 let

357366 optimizeBranch root (Can.CaseBranch pattern branch) =

358367 do defs <- destructHelp (Opt.VarLocal root) pattern []

359− obranch <- optimizeTail cycle name argNames branch

368+ obranch <- optimizeTail cycle rootName argNames branch

360369 pure (pattern, foldr Opt.Let obranch defs)

361370 in

362− do oexpr <- optimize cycle expr

371+ do temp <- Names.generate

372+ oexpr <- optimize cycle expr

363373 case oexpr of

364374 Opt.VarLocal root ->

365− Case.optimize root <$> traverse (optimizeBranch root) branches

375+ Case.optimize temp root <$> traverse (optimizeBranch root) branches

366376

367377 _ ->

368− do root <- Names.generate

369− Case.optimize root <$> traverse (optimizeBranch root) branches

378+ Case.optimize temp temp <$> traverse (optimizeBranch temp) branches

370379

371380 _ ->

372381 optimize cycle locExpr

@@ -387,7 +396,7 @@ toTailDef name argNames defss body =

387396hasTailCall :: Opt.Expr -> Bool

388397hasTailCall expression =

389398 case expression of

390− Opt.TailCall _ _ _ ->

399+ Opt.TailCall _ _ ->

391400 True

392401

393402 Opt.If branches finally ->

@@ -396,7 +405,7 @@ hasTailCall expression =

396405 Opt.Let _ body ->

397406 hasTailCall body

398407

399− Opt.Case _ _ branches ->

408+ Opt.Case _ _ _ branches ->

400409 any (hasTailCall . snd) branches

401410

402411 _ ->

src/Optimize/Module.hs+6−15

@@ -15,6 +15,7 @@ import qualified Data.Set as Set

1515import qualified AST.Canonical as Can

1616import qualified AST.Optimized as Opt

1717import qualified AST.Module.Name as ModuleName

18+import qualified Data.Index as Index

1819import qualified Elm.Name as N

1920import qualified Optimize.Expression as Expr

2021import qualified Optimize.Names as Names

@@ -58,23 +59,13 @@ addUnions home unions (Graph fields nodes) =

5859

5960addUnion :: ModuleName.Canonical -> Can.Union -> Nodes -> Nodes

6061addUnion home (Can.Union _ ctors) nodes =

61− foldr (addCtor home) nodes ctors

62+ Map.union nodes $

63+ Map.fromList (Index.indexedMap (ctorToNode home) ctors)

6264

6365

64−addCtor :: ModuleName.Canonical -> (N.Name, [t]) -> Nodes -> Nodes

65−addCtor home (ctor, args) nodes =

66− let

67− argNames =

68− map N.localFromInt [ 1 .. length args ]

69−

70− function =

71− Opt.Function argNames $

72− Opt.Ctor ctor (map Opt.VarLocal argNames)

73−

74− node =

75− Opt.Define function Set.empty Set.empty

76− in

77− Map.insert (Opt.Global home ctor) node nodes

66+ctorToNode :: ModuleName.Canonical -> Index.ZeroBased -> (N.Name, [t]) -> (Opt.Global, Opt.Node)

67+ctorToNode home index (name, args) =

68+ ( Opt.Global home name, Opt.Ctor name index (length args) )

7869

7970

8071

src/Optimize/Port.hs+14−14

@@ -68,13 +68,13 @@ toEncoder tipe =

6868 let

6969 encodeField (name, fieldType) =

7070 do encoder <- toEncoder fieldType

71− let value = Opt.Call encoder [Opt.Access (Opt.VarLocal "r") name]

71+ let value = Opt.Call encoder [Opt.Access (Opt.VarLocal N.dollar) name]

7272 return $ Opt.Tuple (Opt.Str name) value Nothing

7373 in

7474 do object <- encode "object"

7575 keyValuePairs <- traverse encodeField (Map.toList fields)

7676 Names.registerFieldDict fields $

77− Opt.Function ["r"] (Opt.Call object [Opt.List keyValuePairs])

77+ Opt.Function [N.dollar] (Opt.Call object [Opt.List keyValuePairs])

7878

7979

8080

@@ -86,12 +86,12 @@ encodeMaybe tipe =

8686 do null <- encode "null"

8787 encoder <- toEncoder tipe

8888

89− let test = (DT.Empty, DT.IsCtor 2 "Nothing")

90− let just = Opt.Call encoder [ Opt.CtorAccess (Opt.VarLocal "m") Index.first ]

89+ let test = (DT.Empty, DT.IsCtor 2 "Just" Index.first)

90+ let just = Opt.Call encoder [ Opt.Index (Opt.VarLocal N.dollar) 0 ]

9191 let leaf expr = Opt.Leaf (Opt.Inline expr)

9292

93− return $ Opt.Function ["m"] $

94− Opt.Case "m" (Opt.Chain [test] (leaf null) (leaf just)) []

93+ return $ Opt.Function [N.dollar] $

94+ Opt.Case N.dollar N.dollar (Opt.Chain [test] (leaf just) (leaf null)) []

9595

9696

9797encodeList :: Can.Type -> Names.Tracker Opt.Expr

@@ -100,8 +100,8 @@ encodeList tipe =

100100 map_ <- Names.registerGlobal ModuleName.list "map"

101101 encoder <- toEncoder tipe

102102 return $

103− Opt.Function ["xs"] $

104− Opt.Call list [ Opt.Call map_ [ encoder, Opt.VarLocal "xs" ] ]

103+ Opt.Function [N.dollar] $

104+ Opt.Call list [ Opt.Call map_ [ encoder, Opt.VarLocal N.dollar ] ]

105105

106106

107107encodeArray :: Can.Type -> Names.Tracker Opt.Expr

@@ -110,8 +110,8 @@ encodeArray tipe =

110110 map_ <- Names.registerGlobal ModuleName.array "map"

111111 encoder <- toEncoder tipe

112112 return $

113− Opt.Function ["xs"] $

114− Opt.Call array [ Opt.Call map_ [ encoder, Opt.VarLocal "xs" ] ]

113+ Opt.Function [N.dollar] $

114+ Opt.Call array [ Opt.Call map_ [ encoder, Opt.VarLocal N.dollar ] ]

115115

116116

117117encodeTuple :: Can.Type -> Can.Type -> Maybe Can.Type -> Names.Tracker Opt.Expr

@@ -119,18 +119,18 @@ encodeTuple a b maybeC =

119119 let

120120 convert index tipe =

121121 do encoder <- toEncoder tipe

122− return $ Opt.Call encoder [ Opt.CtorAccess (Opt.VarLocal "t") index ]

122+ return $ Opt.Call encoder [ Opt.Index (Opt.VarLocal N.dollar) index ]

123123 in

124− Opt.Function ["t"] <$> (

124+ Opt.Function [N.dollar] <$> (

125125 Opt.Call

126126 <$> encode "list"

127127 <*>

128128 case maybeC of

129129 Nothing ->

130− Index.indexedTraverse convert [a,b]

130+ sequence [ convert 0 a, convert 1 b ]

131131

132132 Just c ->

133− Index.indexedTraverse convert [a,b,c]

133+ sequence [ convert 0 a, convert 1 b, convert 2 c ]

134134 )

135135

136136