ab8ff11 · elk · git.iko.soy

git.iko.soy/elk

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Get rid of `split` and make `repeat` significantly faster

ab8ff11Evan Czaplicki13 years ago

libraries/List.elm−7

compare with master

unifiedsplit

@@ -191,13 +191,6 @@ unzip pairs =

191 [] -> ([],[])

192 (x,y)::ps -> let (xs,ys) = (unzip ps) in (x::xs,y::ys)

193

194−{-| Split a list with a given seperator.

195−

196− split "," "hello,there,friend" == ["hello", "there", "friend"]

197−-}

198−split : [a] -> [a] -> [[a]]

199−split = Native.List.split

200−

201{-| Places the given value between all of the lists in the second

194{-| Places the given value between all of the lists in the second

202argument and concatenates the result.

195argument and concatenates the result.

203

196

libraries/Native/List.js+9−64

@@ -241,13 +241,14 @@ Elm.Native.List.make = function(elm) {

241 return xs;

242 }

243

244− function repeat(n, a) {

244+ function repeat(n, x) {

245− var arr = [];

245+ var arr = [];

246+ var pattern = [x];

246− while (n > 0) {

247+ while (n > 0) {

247− arr.push(a);

248+ if (n & 1) arr += pattern;

248− --n;

249+ n >>= 1, pattern += pattern;

249− }

250+ }

250− return fromArray(arr);

251+ return fromArray(arr);

251 }

252 }

252

253

253 function join(sep, xss) {

254 function join(sep, xss) {

@@ -263,61 +264,6 @@ Elm.Native.List.make = function(elm) {

263 return fromArray(out);

264 return fromArray(out);

264 }

265 }

265

266

266− function split(seperator, list) {

267− var array = toArray(list);

268− var alen = array.length;

269− if (alen === 0) {

270− // splitting an empty list is a list of lists: [[]]

271− return Cons(Nil,Nil);

272− }

273−

274− var sep = toArray(seperator);

275− var seplen = sep.length;

276− if (seplen === 0) {

277− // splitting with an empty sep is a list of all elements

278− // Same as (map (\x -> [x]) list)

279− var out = Nil;

280− for (var i = alen; i--; ) {

281− out = Cons(Cons(array[i],Nil), out);

282− }

283− return out;

284− }

285−

286− var matches = [-seplen];

287− var sepStart = sep[0];

288− var len = alen - seplen + 1;

289− for (var i = 0; i < len; ++i) {

290− if (Utils.eq(array[i], sepStart)) {

291− var match = true;

292− for (var j = seplen; --j; ) {

293− if (!Utils.eq(array[i+j], sep[j])) { match = false; break; }

294− }

295− if (match) {

296− matches.push(i);

297− i += seplen - 1;

298− }

299− }

300− }

301−

302− // shortcut in case of no matches

303− if (matches.length === 0) {

304− return Cons(list,Nil);

305− }

306−

307− var out = Nil;

308− var index = alen - 1;

309− for (var i = matches.length; i--; ) {

310− var temp = Nil;

311− var stop = matches[i] + seplen - 1;

312− for ( ; index > stop; --index ) {

313− temp = Cons(array[index], temp);

314− }

315− out = Cons(temp,out);

316− index -= seplen;

317− }

318− return out;

319− }

320−

321 Elm.Native.List.values = {

267 Elm.Native.List.values = {

322 Nil:Nil,

268 Nil:Nil,

323 Cons:Cons,

269 Cons:Cons,

@@ -355,8 +301,7 @@ Elm.Native.List.make = function(elm) {

355 drop:F2(drop),

301 drop:F2(drop),

356 repeat:F2(repeat),

302 repeat:F2(repeat),

357

303

358− join:F2(join),

304+ join:F2(join)

359− split:F2(split)

360 };

305 };

361 return elm.Native.List = Elm.Native.List.values;

306 return elm.Native.List = Elm.Native.List.values;

362

307