Source

text / Data / Text.hs

The default branch has multiple heads

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
{-# LANGUAGE BangPatterns, CPP, Rank2Types #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}

-- |
-- Module      : Data.Text
-- Copyright   : (c) Tom Harper 2008-2009,
--               (c) Bryan O'Sullivan 2009,
--               (c) Duncan Coutts 2009
--
-- License     : BSD-style
-- Maintainer  : bos@serpentine.com, rtomharper@googlemail.com,
--               duncan@haskell.org
-- Stability   : experimental
-- Portability : GHC
--
-- A time and space-efficient implementation of Unicode text using
-- packed Word16 arrays.  Suitable for performance critical use, both
-- in terms of large data quantities and high speed.
--
-- This module is intended to be imported @qualified@, to avoid name
-- clashes with "Prelude" functions, e.g.
--
-- > import qualified Data.Text as T

module Data.Text
    (
    -- * Fusion
    -- $fusion

    -- * Types
      Text

    -- * Creation and elimination
    , pack
    , unpack
    , singleton
    , empty

    -- * Basic interface
    , cons
    , snoc
    , append
    , uncons
    , head
    , last
    , tail
    , init
    , null
    , length

    -- * Transformations
    , map
    , intercalate
    , intersperse
    , transpose
    , reverse
    , replace

    -- ** Case conversion
    -- $case
    , toCaseFold
    , toLower
    , toUpper

    -- ** Justification
    , justifyLeft
    , justifyRight
    , center

    -- * Folds
    , foldl
    , foldl'
    , foldl1
    , foldl1'
    , foldr
    , foldr1

    -- ** Special folds
    , concat
    , concatMap
    , any
    , all
    , maximum
    , minimum

    -- * Construction

    -- ** Scans
    , scanl
    , scanl1
    , scanr
    , scanr1

    -- ** Accumulating maps
    , mapAccumL
    , mapAccumR

    -- ** Generation and unfolding
    , replicate
    , unfoldr
    , unfoldrN

    -- * Substrings

    -- ** Breaking strings
    , take
    , drop
    , takeWhile
    , dropWhile
    , dropWhileEnd
    , dropAround
    , strip
    , stripStart
    , stripEnd
    , splitAt
    , spanBy
    , break
    , breakEnd
    , breakBy
    , group
    , groupBy
    , inits
    , tails

    -- ** Breaking into many substrings
    -- $split
    , split
    , splitBy
    , chunksOf

    -- ** Breaking into lines and words
    , lines
    --, lines'
    , words
    , unlines
    , unwords

    -- * Predicates
    , isPrefixOf
    , isSuffixOf
    , isInfixOf

    -- * Searching
    , filter
    , find
    , findBy
    , partitionBy

    -- , findSubstring
    
    -- * Indexing
    -- $index
    , index
    , findIndex
    , count

    -- * Zipping and unzipping
    , zip
    , zipWith

    -- -* Ordered text
    -- , sort
    ) where

import Prelude (Char, Bool(..), Functor(..), Int, Maybe(..), String,
                Eq(..), Ord(..), (++),
                Read(..), Show(..),
                (&&), (||), (+), (-), (.), ($), (>>), (*),
                div, error, not, return, otherwise)
#if defined(HAVE_DEEPSEQ)
import Control.DeepSeq (NFData)
#endif
import Control.Exception (assert)
import Data.Char (isSpace)
import Data.Data (Data(gfoldl, toConstr, gunfold, dataTypeOf))
#if __GLASGOW_HASKELL__ >= 612
import Data.Data (mkNoRepType)
#else
import Data.Data (mkNorepType)
#endif
import Control.Monad (foldM)
import Control.Monad.ST (ST)
import qualified Data.Text.Array as A
import qualified Data.List as L
import Data.Monoid (Monoid(..))
import Data.Word (Word16)
import Data.String (IsString(..))
import qualified Data.Text.Fusion as S
import qualified Data.Text.Fusion.Common as S
import Data.Text.Fusion (stream, reverseStream, unstream)
import Data.Text.Internal (Text(..), empty, text, textP)
import qualified Prelude as P
import Data.Text.Unsafe (iter, iter_, reverseIter, unsafeHead, unsafeTail)
import Data.Text.UnsafeChar (unsafeChr)
import qualified Data.Text.Encoding.Utf16 as U16
import Data.Text.Search (indices)

-- $fusion
--
-- Most of the functions in this module are subject to /fusion/,
-- meaning that a pipeline of such functions will usually allocate at
-- most one 'Text' value.

instance Eq Text where
    t1 == t2 = stream t1 == stream t2
    {-# INLINE (==) #-}

instance Ord Text where
    compare t1 t2 = compare (stream t1) (stream t2)
    {-# INLINE compare #-}

instance Show Text where
    showsPrec p ps r = showsPrec p (unpack ps) r

instance Read Text where
    readsPrec p str = [(pack x,y) | (x,y) <- readsPrec p str]

instance Monoid Text where
    mempty  = empty
    mappend = append
    mconcat = concat

instance IsString Text where
    fromString = pack

#if defined(HAVE_DEEPSEQ)
instance NFData Text
#endif

-- This instance preserves data abstraction at the cost of inefficiency.
-- We omit reflection services for the sake of data abstraction.
-- 
-- This instance was created by copying the behavior of Data.Set and
-- Data.Map. If you feel a mistake has been made, please feel free to
-- submit improvements.
--
-- Original discussion is archived here:

--  "could we get a Data instance for Data.Text.Text?"
--  http://groups.google.com/group/haskell-cafe/browse_thread/thread/b5bbb1b28a7e525d/0639d46852575b93

instance Data Text where
  gfoldl f z txt = z pack `f` (unpack txt)
  toConstr _     = error "Data.Text.Text.toConstr"
  gunfold _ _    = error "Data.Text.Text.gunfold"
#if __GLASGOW_HASKELL__ >= 612
  dataTypeOf _   = mkNoRepType "Data.Text.Text"
#else
  dataTypeOf _   = mkNorepType "Data.Text.Text"
#endif

-- -----------------------------------------------------------------------------
-- * Conversion to/from 'Text'

-- | /O(n)/ Convert a 'String' into a 'Text'.  Subject to fusion.
pack :: String -> Text
pack = unstream . S.streamList
{-# INLINE [1] pack #-}

-- | /O(n)/ Convert a Text into a String.  Subject to fusion.
unpack :: Text -> String
unpack = S.unstreamList . stream
{-# INLINE [1] unpack #-}

-- | /O(1)/ Convert a character into a Text.
-- Subject to fusion.
singleton :: Char -> Text
singleton = unstream . S.singleton
{-# INLINE [1] singleton #-}

-- -----------------------------------------------------------------------------
-- * Basic functions

-- | /O(n)/ Adds a character to the front of a 'Text'.  This function
-- is more costly than its 'List' counterpart because it requires
-- copying a new array.  Subject to fusion.
cons :: Char -> Text -> Text
cons c t = unstream (S.cons c (stream t))
{-# INLINE cons #-}

-- | /O(n)/ Adds a character to the end of a 'Text'.  This copies the
-- entire array in the process, unless fused.  Subject to fusion.
snoc :: Text -> Char -> Text
snoc t c = unstream (S.snoc (stream t) c)
{-# INLINE snoc #-}

-- | /O(n)/ Appends one 'Text' to the other by copying both of them
-- into a new 'Text'.  Subject to fusion.
append :: Text -> Text -> Text
append (Text arr1 off1 len1) (Text arr2 off2 len2) = Text (A.run x) 0 len
    where
      len = len1+len2
      x = do
        arr <- A.unsafeNew len
        copy arr 0 arr1 off1 len1
        copy arr len1 arr2 off2 (len1+len2)
        return arr
{-# INLINE append #-}

{-# RULES
"TEXT append -> fused" [~1] forall t1 t2.
    append t1 t2 = unstream (S.append (stream t1) (stream t2))
"TEXT append -> unfused" [1] forall t1 t2.
    unstream (S.append (stream t1) (stream t2)) = append t1 t2
 #-}

copy :: forall s. A.MArray s Word16 -> Int -> A.Array Word16 -> Int -> Int
     -> ST s ()
copy dest i0 src j0 top = go i0 j0
  where
    go i j | i >= top  = return ()
           | otherwise = do A.unsafeWrite dest i (src `A.unsafeIndex` j)
                            go (i+1) (j+1)

-- | /O(1)/ Returns the first character of a 'Text', which must be
-- non-empty.  Subject to fusion.
head :: Text -> Char
head t = S.head (stream t)
{-# INLINE head #-}

-- | /O(1)/ Returns the first character and rest of a 'Text', or
-- 'Nothing' if empty. Subject to fusion.
uncons :: Text -> Maybe (Char, Text)
uncons t@(Text arr off len)
    | len <= 0  = Nothing
    | otherwise = Just (c, textP arr (off+d) (len-d))
    where (c,d) = iter t 0
{-# INLINE [1] uncons #-}

-- | Lifted from Control.Arrow and specialized.
second :: (b -> c) -> (a,b) -> (a,c)
second f (a, b) = (a, f b)

{-# RULES
"TEXT uncons -> fused" [~1] forall t.
    uncons t = fmap (second unstream) (S.uncons (stream t))
"TEXT uncons -> unfused" [1] forall t.
    fmap (second unstream) (S.uncons (stream t)) = uncons t
  #-}

-- | /O(1)/ Returns the last character of a 'Text', which must be
-- non-empty.  Subject to fusion.
last :: Text -> Char
last (Text arr off len)
    | len <= 0                 = emptyError "last"
    | n < 0xDC00 || n > 0xDFFF = unsafeChr n
    | otherwise                = U16.chr2 n0 n
    where n  = A.unsafeIndex arr (off+len-1)
          n0 = A.unsafeIndex arr (off+len-2)
{-# INLINE [1] last #-}

{-# RULES
"TEXT last -> fused" [~1] forall t.
    last t = S.last (stream t)
"TEXT last -> unfused" [1] forall t.
    S.last (stream t) = last t
  #-}

-- | /O(1)/ Returns all characters after the head of a 'Text', which
-- must be non-empty.  Subject to fusion.
tail :: Text -> Text
tail t@(Text arr off len)
    | len <= 0  = emptyError "tail"
    | otherwise = textP arr (off+d) (len-d)
    where d = iter_ t 0
{-# INLINE [1] tail #-}

{-# RULES
"TEXT tail -> fused" [~1] forall t.
    tail t = unstream (S.tail (stream t))
"TEXT tail -> unfused" [1] forall t.
    unstream (S.tail (stream t)) = tail t
 #-}

-- | /O(1)/ Returns all but the last character of a 'Text', which must
-- be non-empty.  Subject to fusion.
init :: Text -> Text
init (Text arr off len) | len <= 0                   = emptyError "init"
                        | n >= 0xDC00 && n <= 0xDFFF = textP arr off (len-2)
                        | otherwise                  = textP arr off (len-1)
    where
      n = A.unsafeIndex arr (off+len-1)
{-# INLINE [1] init #-}

{-# RULES
"TEXT init -> fused" [~1] forall t.
    init t = unstream (S.init (stream t))
"TEXT init -> unfused" [1] forall t.
    unstream (S.init (stream t)) = init t
 #-}

-- | /O(1)/ Tests whether a 'Text' is empty or not.  Subject to
-- fusion.
null :: Text -> Bool
null (Text _arr _off len) = assert (len >= 0) $ len <= 0
{-# INLINE [1] null #-}

{-# RULES
"TEXT null -> fused" [~1] forall t.
    null t = S.null (stream t)
"TEXT null -> unfused" [1] forall t.
    S.null (stream t) = null t
 #-}

-- | /O(1)/ Tests whether a 'Text' contains exactly one character.
-- Subject to fusion.
isSingleton :: Text -> Bool
isSingleton = S.isSingleton . stream
{-# INLINE isSingleton #-}

-- | /O(n)/ Returns the number of characters in a 'Text'.
-- Subject to fusion.
length :: Text -> Int
length t = S.length (stream t)
{-# INLINE length #-}

-- -----------------------------------------------------------------------------
-- * Transformations
-- | /O(n)/ 'map' @f@ @t@ is the 'Text' obtained by applying @f@ to
-- each element of @t@.  Subject to fusion.
map :: (Char -> Char) -> Text -> Text
map f t = unstream (S.map f (stream t))
{-# INLINE [1] map #-}

-- | /O(n)/ The 'intercalate' function takes a 'Text' and a list of
-- 'Text's and concatenates the list after interspersing the first
-- argument between each element of the list.
intercalate :: Text -> [Text] -> Text
intercalate t = concat . (L.intersperse t)
{-# INLINE intercalate #-}

-- | /O(n)/ The 'intersperse' function takes a character and places it
-- between the characters of a 'Text'.  Subject to fusion.
intersperse     :: Char -> Text -> Text
intersperse c t = unstream (S.intersperse c (stream t))
{-# INLINE intersperse #-}

-- | /O(n)/ Reverse the characters of a string. Subject to fusion.
reverse :: Text -> Text
reverse t = S.reverse (stream t)
{-# INLINE reverse #-}

-- | /O(m+n)/ Replace every occurrence of one substring with another.
replace :: Text                 -- ^ Text to search for
        -> Text                 -- ^ Replacement text
        -> Text                 -- ^ Input text
        -> Text
replace s d = intercalate d . split s
{-# INLINE replace #-}

-- ----------------------------------------------------------------------------
-- ** Case conversions (folds)

-- $case
--
-- When case converting 'Text' values, do not use combinators like
-- @map toUpper@ to case convert each character of a string
-- individually, as this gives incorrect results according to the
-- rules of some writing systems.  The whole-string case conversion
-- functions from this module, such as @toUpper@, obey the correct
-- case conversion rules.  As a result, these functions may map one
-- input character to two or three output characters. For examples,
-- see the documentation of each function.

-- | /O(n)/ Convert a string to folded case.  This function is mainly
-- useful for performing caseless (also known as case insensitive)
-- string comparisons.
--
-- A string @x@ is a caseless match for a string @y@ if and only if:
--
-- @toCaseFold x == toCaseFold y@
--
-- The result string may be longer than the input string, and may
-- differ from applying 'toLower' to the input string.  For instance,
-- the Armenian small ligature \"&#xfb13;\" (men now, U+FB13) is case
-- folded to the sequence \"&#x574;\" (men, U+0574) followed by
-- \"&#x576;\" (now, U+0576), while the Greek \"&#xb5;\" (micro sign,
-- U+00B5) is case folded to \"&#x3bc;\" (small letter mu, U+03BC)
-- instead of itself.
toCaseFold :: Text -> Text
toCaseFold t = unstream (S.toCaseFold (stream t))
{-# INLINE [0] toCaseFold #-}

-- | /O(n)/ Convert a string to lower case, using simple case
-- conversion.  The result string may be longer than the input string.
-- For instance, \"&#x130;\" (Latin capital letter I with dot above,
-- U+0130) maps to the sequence \"i\" (Latin small letter i, U+0069) followed
-- by \" &#x307;\" (combining dot above, U+0307).
toLower :: Text -> Text
toLower t = unstream (S.toLower (stream t))
{-# INLINE toLower #-}

-- | /O(n)/ Convert a string to upper case, using simple case
-- conversion.  The result string may be longer than the input string.
-- For instance, the German \"&#xdf;\" (eszett, U+00DF) maps to the
-- two-letter sequence \"SS\".
toUpper :: Text -> Text
toUpper t = unstream (S.toUpper (stream t))
{-# INLINE toUpper #-}

-- | /O(n)/ Left-justify a string to the given length, using the
-- specified fill character on the right. Subject to fusion. Examples:
--
-- > justifyLeft 7 'x' "foo"    == "fooxxxx"
-- > justifyLeft 3 'x' "foobar" == "foobar"
justifyLeft :: Int -> Char -> Text -> Text
justifyLeft k c t
    | len >= k  = t
    | otherwise = t `append` replicateChar (k-len) c
  where len = length t
{-# INLINE [1] justifyLeft #-}

{-# RULES
"TEXT justifyLeft -> fused" [~1] forall k c t.
    justifyLeft k c t = unstream (S.justifyLeftI k c (stream t))
"TEXT justifyLeft -> unfused" [1] forall k c t.
    unstream (S.justifyLeftI k c (stream t)) = justifyLeft k c t
  #-}

-- | /O(n)/ Right-justify a string to the given length, using the
-- specified fill character on the left. Examples:
--
-- > justifyRight 7 'x' "bar"    == "xxxxbar"
-- > justifyRight 3 'x' "foobar" == "foobar"
justifyRight :: Int -> Char -> Text -> Text
justifyRight k c t
    | len >= k  = t
    | otherwise = replicateChar (k-len) c `append` t
  where len = length t
{-# INLINE justifyRight #-}

-- | /O(n)/ Center a string to the given length, using the
-- specified fill character on either side. Examples:
--
-- > center 8 'x' "HS" = "xxxHSxxx"
center :: Int -> Char -> Text -> Text
center k c t
    | len >= k  = t
    | otherwise = replicateChar l c `append` t `append` replicateChar r c
  where len = length t
        d   = k - len
        r   = d `div` 2
        l   = d - r
{-# INLINE center #-}

-- | /O(n)/ The 'transpose' function transposes the rows and columns
-- of its 'Text' argument.  Note that this function uses 'pack',
-- 'unpack', and the list version of transpose, and is thus not very
-- efficient.
transpose :: [Text] -> [Text]
transpose ts = P.map pack (L.transpose (P.map unpack ts))

-- -----------------------------------------------------------------------------
-- * Reducing 'Text's (folds)

-- | /O(n)/ 'foldl', applied to a binary operator, a starting value
-- (typically the left-identity of the operator), and a 'Text',
-- reduces the 'Text' using the binary operator, from left to right.
-- Subject to fusion.
foldl :: (b -> Char -> b) -> b -> Text -> b
foldl f z t = S.foldl f z (stream t)
{-# INLINE foldl #-}

-- | /O(n)/ A strict version of 'foldl'.  Subject to fusion.
foldl' :: (b -> Char -> b) -> b -> Text -> b
foldl' f z t = S.foldl' f z (stream t)
{-# INLINE foldl' #-}

-- | /O(n)/ A variant of 'foldl' that has no starting value argument,
-- and thus must be applied to a non-empty 'Text'.  Subject to fusion.
foldl1 :: (Char -> Char -> Char) -> Text -> Char
foldl1 f t = S.foldl1 f (stream t)
{-# INLINE foldl1 #-}

-- | /O(n)/ A strict version of 'foldl1'.  Subject to fusion.
foldl1' :: (Char -> Char -> Char) -> Text -> Char
foldl1' f t = S.foldl1' f (stream t)
{-# INLINE foldl1' #-}

-- | /O(n)/ 'foldr', applied to a binary operator, a starting value
-- (typically the right-identity of the operator), and a 'Text',
-- reduces the 'Text' using the binary operator, from right to left.
-- Subject to fusion.
foldr :: (Char -> b -> b) -> b -> Text -> b
foldr f z t = S.foldr f z (stream t)
{-# INLINE foldr #-}

-- | /O(n)/ A variant of 'foldr' that has no starting value argument,
-- and thust must be applied to a non-empty 'Text'.  Subject to
-- fusion.
foldr1 :: (Char -> Char -> Char) -> Text -> Char
foldr1 f t = S.foldr1 f (stream t)
{-# INLINE foldr1 #-}

-- -----------------------------------------------------------------------------
-- ** Special folds

-- | /O(n)/ Concatenate a list of 'Text's.
concat :: [Text] -> Text
concat ts = Text (A.run go) 0 len
  where
    len = L.sum (L.map (\(Text _ _ l) -> l) ts)
    go = do
      arr <- A.unsafeNew len
      let step i (Text a o l) = let j = i + l in copy arr i a o j >> return j
      foldM step 0 ts >> return arr
{-# INLINE concat #-}

-- | /O(n)/ Map a function over a 'Text' that results in a 'Text', and
-- concatenate the results.
concatMap :: (Char -> Text) -> Text -> Text
concatMap f = concat . foldr ((:) . f) []
{-# INLINE concatMap #-}

-- | /O(n)/ 'any' @p@ @t@ determines whether any character in the
-- 'Text' @t@ satisifes the predicate @p@. Subject to fusion.
any :: (Char -> Bool) -> Text -> Bool
any p t = S.any p (stream t)
{-# INLINE any #-}

-- | /O(n)/ 'all' @p@ @t@ determines whether all characters in the
-- 'Text' @t@ satisify the predicate @p@. Subject to fusion.
all :: (Char -> Bool) -> Text -> Bool
all p t = S.all p (stream t)
{-# INLINE all #-}

-- | /O(n)/ 'maximum' returns the maximum value from a 'Text', which
-- must be non-empty. Subject to fusion.
maximum :: Text -> Char
maximum t = S.maximum (stream t)
{-# INLINE maximum #-}

-- | /O(n)/ 'minimum' returns the minimum value from a 'Text', which
-- must be non-empty. Subject to fusion.
minimum :: Text -> Char
minimum t = S.minimum (stream t)
{-# INLINE minimum #-}

-- -----------------------------------------------------------------------------
-- * Building 'Text's

-- | /O(n)/ 'scanl' is similar to 'foldl', but returns a list of
-- successive reduced values from the left. Subject to fusion.
--
-- > scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]
--
-- Note that
--
-- > last (scanl f z xs) == foldl f z xs.
scanl :: (Char -> Char -> Char) -> Char -> Text -> Text
scanl f z t = unstream (S.scanl f z (stream t))
{-# INLINE scanl #-}

-- | /O(n)/ 'scanl1' is a variant of 'scanl' that has no starting
-- value argument.  Subject to fusion.
--
-- > scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]
scanl1 :: (Char -> Char -> Char) -> Text -> Text
scanl1 f t | null t    = empty
           | otherwise = scanl f (unsafeHead t) (unsafeTail t)
{-# INLINE scanl1 #-}

-- | /O(n)/ 'scanr' is the right-to-left dual of 'scanl'.
--
-- > scanr f v == reverse . scanl (flip f) v . reverse
scanr :: (Char -> Char -> Char) -> Char -> Text -> Text
scanr f z = S.reverse . S.reverseScanr f z . reverseStream
{-# INLINE scanr #-}

-- | /O(n)/ 'scanr1' is a variant of 'scanr' that has no starting
-- value argument.  Subject to fusion.
scanr1 :: (Char -> Char -> Char) -> Text -> Text
scanr1 f t | null t    = empty
           | otherwise = scanr f (last t) (init t)
{-# INLINE scanr1 #-}

-- | /O(n)/ Like a combination of 'map' and 'foldl'. Applies a
-- function to each element of a 'Text', passing an accumulating
-- parameter from left to right, and returns a final 'Text'.
mapAccumL :: (a -> Char -> (a,Char)) -> a -> Text -> (a, Text)
mapAccumL f s t = case uncons t of
                    Nothing -> (s, empty)
                    Just (x, xs) -> (s'', cons y ys)
                        where (s', y ) = f s x
                              (s'',ys) = mapAccumL f s' xs

-- | The 'mapAccumR' function behaves like a combination of 'map' and
-- 'foldr'; it applies a function to each element of a 'Text', passing
-- an accumulating parameter from right to left, and returning a final
-- value of this accumulator together with the new 'Text'.
mapAccumR :: (a -> Char -> (a,Char)) -> a -> Text -> (a, Text)
mapAccumR f s t = case uncons t of
                    Nothing -> (s, empty)
                    Just (x, xs) ->  (s'', cons y ys)
                        where (s'',y ) = f s' x
                              (s', ys) = mapAccumR f s xs

-- -----------------------------------------------------------------------------
-- ** Generating and unfolding 'Text's

-- | /O(n*m)/ 'replicate' @n@ @t@ is a 'Text' consisting of the input
-- @t@ repeated @n@ times.
replicate :: Int -> Text -> Text
replicate n t@(Text a o l)
    | n <= 0 || l <= 0 = empty
    | n == 1           = t
    | isSingleton t    = replicateChar n (unsafeHead t)
    | otherwise        = Text (A.run x) 0 len
  where
    len = l * n
    x = do
      arr <- A.unsafeNew len
      let loop !d !i | i >= n    = return arr
                     | otherwise = let m = d + l
                                   in copy arr d a o m >> loop m (i+1)
      loop 0 0
{-# INLINE [1] replicate #-}

{-# RULES
"TEXT replicate/singleton -> replicateChar" [~1] forall n c.
    replicate n (singleton c) = replicateChar n c
  #-}

-- | /O(n)/ 'replicateChar' @n@ @c@ is a 'Text' of length @n@ with @c@ the
-- value of every element. Subject to fusion.
replicateChar :: Int -> Char -> Text
replicateChar n c = unstream (S.replicateCharI n c)
{-# INLINE replicateChar #-}

-- | /O(n)/, where @n@ is the length of the result. The 'unfoldr'
-- function is analogous to the List 'L.unfoldr'. 'unfoldr' builds a
-- 'Text' from a seed value. The function takes the element and
-- returns 'Nothing' if it is done producing the 'Text', otherwise
-- 'Just' @(a,b)@.  In this case, @a@ is the next 'Char' in the
-- string, and @b@ is the seed value for further production. Subject
-- to fusion.
unfoldr     :: (a -> Maybe (Char,a)) -> a -> Text
unfoldr f s = unstream (S.unfoldr f s)
{-# INLINE unfoldr #-}

-- | /O(n)/ Like 'unfoldr', 'unfoldrN' builds a 'Text' from a seed
-- value. However, the length of the result should be limited by the
-- first argument to 'unfoldrN'. This function is more efficient than
-- 'unfoldr' when the maximum length of the result is known and
-- correct, otherwise its performance is similar to 'unfoldr'. Subject
-- to fusion.
unfoldrN     :: Int -> (a -> Maybe (Char,a)) -> a -> Text
unfoldrN n f s = unstream (S.unfoldrN n f s)
{-# INLINE unfoldrN #-}

-- -----------------------------------------------------------------------------
-- * Substrings

-- | /O(n)/ 'take' @n@, applied to a 'Text', returns the prefix of the
-- 'Text' of length @n@, or the 'Text' itself if @n@ is greater than
-- the length of the Text. Subject to fusion.
take :: Int -> Text -> Text
take n t@(Text arr off len)
    | n <= 0    = empty
    | n >= len  = t
    | otherwise = Text arr off (loop 0 0)
  where
      loop !i !cnt
           | i >= len || cnt >= n = i
           | otherwise            = loop (i+d) (cnt+1)
           where d = iter_ t i
{-# INLINE [1] take #-}

{-# RULES
"TEXT take -> fused" [~1] forall n t.
    take n t = unstream (S.take n (stream t))
"TEXT take -> unfused" [1] forall n t.
    unstream (S.take n (stream t)) = take n t
  #-}

-- | /O(n)/ 'drop' @n@, applied to a 'Text', returns the suffix of the
-- 'Text' of length @n@, or the empty 'Text' if @n@ is greater than the
-- length of the 'Text'. Subject to fusion.
drop :: Int -> Text -> Text
drop n t@(Text arr off len)
    | n <= 0    = t
    | n >= len  = empty
    | otherwise = loop 0 0
  where loop !i !cnt
            | i >= len || cnt >= n   = Text arr (off+i) (len-i)
            | otherwise              = loop (i+d) (cnt+1)
            where d = iter_ t i
{-# INLINE [1] drop #-}

{-# RULES
"TEXT drop -> fused" [~1] forall n t.
    drop n t = unstream (S.drop n (stream t))
"TEXT drop -> unfused" [1] forall n t.
    unstream (S.drop n (stream t)) = drop n t
  #-}

-- | /O(n)/ 'takeWhile', applied to a predicate @p@ and a 'Text',
-- returns the longest prefix (possibly empty) of elements that
-- satisfy @p@.  Subject to fusion.
takeWhile :: (Char -> Bool) -> Text -> Text
takeWhile p t@(Text arr off len) = loop 0
  where loop !i | i >= len    = t
                | p c         = loop (i+d)
                | otherwise   = textP arr off i
            where (c,d)       = iter t i
{-# INLINE [1] takeWhile #-}

{-# RULES
"TEXT takeWhile -> fused" [~1] forall p t.
    takeWhile p t = unstream (S.takeWhile p (stream t))
"TEXT takeWhile -> unfused" [1] forall p t.
    unstream (S.takeWhile p (stream t)) = takeWhile p t
  #-}

-- | /O(n)/ 'dropWhile' @p@ @t@ returns the suffix remaining after
-- 'takeWhile' @p@ @t@. Subject to fusion.
dropWhile :: (Char -> Bool) -> Text -> Text
dropWhile p t@(Text arr off len) = loop 0 0
  where loop !i !l | l >= len  = empty
                   | p c       = loop (i+d) (l+d)
                   | otherwise = Text arr (off+i) (len-l)
            where (c,d)        = iter t i
{-# INLINE [1] dropWhile #-}

{-# RULES
"TEXT dropWhile -> fused" [~1] forall p t.
    dropWhile p t = unstream (S.dropWhile p (stream t))
"TEXT dropWhile -> unfused" [1] forall p t.
    unstream (S.dropWhile p (stream t)) = dropWhile p t
  #-}

-- | /O(n)/ 'dropWhileEnd' @p@ @t@ returns the prefix remaining after
-- dropping characters that fail the predicate @p@ from the end of
-- @t@.  Subject to fusion.
-- Examples:
--
-- > dropWhileEnd (=='.') "foo..." == "foo"
dropWhileEnd :: (Char -> Bool) -> Text -> Text
dropWhileEnd p t@(Text arr off len) = loop (len-1) len
  where loop !i !l | l <= 0    = empty
                   | p c       = loop (i+d) (l+d)
                   | otherwise = Text arr off l
            where (c,d)        = reverseIter t i
{-# INLINE [1] dropWhileEnd #-}

{-# RULES
"TEXT dropWhileEnd -> fused" [~1] forall p t.
    dropWhileEnd p t = S.reverse (S.dropWhile p (S.reverseStream t))
"TEXT dropWhileEnd -> unfused" [1] forall p t.
    S.reverse (S.dropWhile p (S.reverseStream t)) = dropWhileEnd p t
  #-}

-- | /O(n)/ 'dropAround' @p@ @t@ returns the substring remaining after
-- dropping characters that fail the predicate @p@ from both the
-- beginning and end of @t@.  Subject to fusion.
dropAround :: (Char -> Bool) -> Text -> Text
dropAround p = dropWhile p . dropWhileEnd p
{-# INLINE [1] dropAround #-}

-- | /O(n)/ Remove leading white space from a string.  Equivalent to:
--
-- > dropWhile isSpace
stripStart :: Text -> Text
stripStart = dropWhile isSpace
{-# INLINE [1] stripStart #-}

-- | /O(n)/ Remove trailing white space from a string.  Equivalent to:
--
-- > dropWhileEnd isSpace
stripEnd :: Text -> Text
stripEnd = dropWhileEnd isSpace
{-# INLINE [1] stripEnd #-}

-- | /O(n)/ Remove leading and trailing white space from a string.
-- Equivalent to:
--
-- > dropAround isSpace
strip :: Text -> Text
strip = dropAround isSpace
{-# INLINE [1] strip #-}

-- | /O(n)/ 'splitAt' @n t@ returns a pair whose first element is a
-- prefix of @t@ of length @n@, and whose second is the remainder of
-- the string. It is equivalent to @('take' n t, 'drop' n t)@.
splitAt :: Int -> Text -> (Text, Text)
splitAt n t@(Text arr off len)
    | n <= 0    = (empty, t)
    | n >= len  = (t, empty)
    | otherwise = (Text arr off k, Text arr (off+k) (len-k))
  where k = loop 0 0
        loop !i !cnt
            | i >= len || cnt >= n = i
            | otherwise            = loop (i+d) (cnt+1)
            where d                = iter_ t i
{-# INLINE splitAt #-}

-- | /O(n)/ 'spanBy', applied to a predicate @p@ and text @t@, returns
-- a pair whose first element is the longest prefix (possibly empty)
-- of @t@ of elements that satisfy @p@, and whose second is the
-- remainder of the list.
spanBy :: (Char -> Bool) -> Text -> (Text, Text)
spanBy p t@(Text arr off len) = (textP arr off k, textP arr (off+k) (len-k))
  where k = loop 0
        loop !i | i >= len || not (p c) = i
                | otherwise             = loop (i+d)
            where (c,d)                 = iter t i
{-# INLINE spanBy #-}

-- | /O(n)/ 'breakBy' is like 'spanBy', but the prefix returned is
-- over elements that fail the predicate @p@.
breakBy :: (Char -> Bool) -> Text -> (Text, Text)
breakBy p = spanBy (not . p)
{-# INLINE breakBy #-}

-- | /O(n)/ Group characters in a string according to a predicate.
groupBy :: (Char -> Char -> Bool) -> Text -> [Text]
groupBy p = loop
  where
    loop t@(Text arr off len)
        | null t    = []
        | otherwise = text arr off n : loop (text arr (off+n) (len-n))
        where (c,d) = iter t 0
              n     = d + findAIndexOrEnd (not . p c) (Text arr (off+d) (len-d))

-- | Returns the /array/ index (in units of 'Word16') at which a
-- character may be found.  This is /not/ the same as the logical
-- index returned by e.g. 'findIndex'.
findAIndexOrEnd :: (Char -> Bool) -> Text -> Int
findAIndexOrEnd q t@(Text _arr _off len) = go 0
    where go !i | i >= len || q c       = i
                | otherwise             = go (i+d)
                where (c,d)             = iter t i
    
-- | /O(n)/ Group characters in a string by equality.
group :: Text -> [Text]
group = groupBy (==)

-- | /O(n)/ Return all initial segments of the given 'Text', shortest
-- first.
inits :: Text -> [Text]
inits t@(Text arr off len) = loop 0
    where loop i | i >= len = [t]
                 | otherwise = Text arr off i : loop (i + iter_ t i)

-- | /O(n)/ Return all final segments of the given 'Text', longest
-- first.
tails :: Text -> [Text]
tails t | null t    = [empty]
        | otherwise = t : tails (unsafeTail t)

-- $split
--
-- Splitting functions in this library do not perform character-wise
-- copies to create substrings; they just construct new 'Text's that
-- are slices of the original.

-- | /O(m+n)/ Break a 'Text' into pieces separated by the first
-- 'Text' argument, consuming the delimiter. An empty delimiter is
-- invalid, and will cause an error to be raised.
--
-- Examples:
--
-- > split "\r\n" "a\r\nb\r\nd\r\ne" == ["a","b","d","e"]
-- > split "aaa"  "aaaXaaaXaaaXaaa"  == ["","X","X","X",""]
-- > split "x"    "x"                == ["",""]
-- 
-- and
--
-- > intercalate s . split s         == id
-- > split (singleton c)             == splitBy (==c)
--
-- In (unlikely) bad cases, this function's time complexity degrades
-- towards /O(n*m)/.
split :: Text -> Text -> [Text]
split pat@(Text _ _ l) src@(Text arr off len)
    | l <= 0          = emptyError "split"
    | isSingleton pat = splitBy (== unsafeHead pat) src
    | otherwise       = go 0 (indices pat src)
  where
    go !s (x:xs) =  textP arr (s+off) (x-s) : go (x+l) xs
    go  s _      = [textP arr (s+off) (len-s)]
{-# INLINE [1] split #-}

{-# RULES
"TEXT split/singleton -> splitBy/==" [~1] forall c t.
    split (singleton c) t = splitBy (==c) t
  #-}

-- | /O(n)/ Splits a 'Text' into components delimited by separators,
-- where the predicate returns True for a separator element.  The
-- resulting components do not contain the separators.  Two adjacent
-- separators result in an empty component in the output.  eg.
--
-- > splitBy (=='a') "aabbaca" == ["","","bb","c",""]
-- > splitBy (=='a') ""        == [""]
splitBy :: (Char -> Bool) -> Text -> [Text]
splitBy _ t@(Text _off _arr 0) = [t]
splitBy p t = loop t
    where loop s | null s'   = [l]
                 | otherwise = l : loop (unsafeTail s')
              where (l, s') = breakBy p s
{-# INLINE splitBy #-}

-- | /O(n)/ Splits a 'Text' into components of length @k@.  The last
-- element may be shorter than the other chunks, depending on the
-- length of the input. Examples:
--
-- > chunksOf 3 "foobarbaz"   == ["foo","bar","baz"]
-- > chunksOf 4 "haskell.org" == ["hask","ell.","org"]
chunksOf :: Int -> Text -> [Text]
chunksOf k = go
  where
    go t = case splitAt k t of
             (a,b) | null a    -> []
                   | otherwise -> a : go b
{-# INLINE chunksOf #-}

-- ----------------------------------------------------------------------------
-- * Searching

-------------------------------------------------------------------------------
-- ** Searching with a predicate

-- | /O(n)/ The 'findBy' function takes a predicate and a 'Text', and
-- returns the first element in matching the predicate, or 'Nothing'
-- if there is no such element.
findBy :: (Char -> Bool) -> Text -> Maybe Char
findBy p t = S.findBy p (stream t)
{-# INLINE findBy #-}

-- | /O(n)/ The 'partitionBy' function takes a predicate and a 'Text',
-- and returns the pair of 'Text's with elements which do and do not
-- satisfy the predicate, respectively; i.e.
--
-- > partitionBy p t == (filter p t, filter (not . p) t)
partitionBy :: (Char -> Bool) -> Text -> (Text, Text)
partitionBy p t = (filter p t, filter (not . p) t)
{-# INLINE partitionBy #-}

-- | /O(n)/ 'filter', applied to a predicate and a 'Text',
-- returns a 'Text' containing those characters that satisfy the
-- predicate.
filter :: (Char -> Bool) -> Text -> Text
filter p t = unstream (S.filter p (stream t))
{-# INLINE filter #-}

-- | /O(n+m)/ Find the first instance of @needle@ (which must be
-- non-'null') in @haystack@.  The first element of the returned tuple
-- is the prefix of @haystack@ before @needle@ is matched.  The second
-- is the remainder of @haystack@, starting with the match.
--
-- Examples:
--
-- > break "::" "a::b::c" ==> ("a", "::b::c")
-- > break "/" "foobar"   ==> ("foobar", "")
--
-- Laws:
--
-- > append prefix match == haystack
-- >   where (prefix, match) = break needle haystack
--
-- If you need to break a string by a substring repeatedly (e.g. you
-- want to break on every instance of a substring), use 'find'
-- instead, as it has lower startup overhead.
--
-- In (unlikely) bad cases, this function's time complexity degrades
-- towards /O(n*m)/.
break :: Text -> Text -> (Text, Text)
break pat src@(Text arr off len)
    | null pat  = emptyError "break"
    | otherwise = case indices pat src of
                    []    -> (src, empty)
                    (x:_) -> (textP arr off x, textP arr (off+x) (len-x))
{-# INLINE break #-}

-- | /O(n+m)/ Similar to 'break', but searches from the end of the string.
--
-- The first element of the returned tuple is the prefix of @haystack@
-- up to and including the last match of @needle@.  The second is the
-- remainder of @haystack@, following the match.
--
-- > breakEnd "::" "a::b::c" ==> ("a::b::", "c")
breakEnd :: Text -> Text -> (Text, Text)
breakEnd pat src = let (a,b) = break (reverse pat) (reverse src)
                   in  (reverse b, reverse a)
{-# INLINE breakEnd #-}

-- | /O(n+m)/ Find all non-overlapping instances of @needle@ in
-- @haystack@.  The first element of the returned pair is the prefix
-- of @haystack@ prior to any matches of @needle@.  The second is a
-- list of pairs.
--
-- The first element of each pair in the list is a span from the
-- beginning of a match to the beginning of the next match, while the
-- second is a span from the beginning of the match to the end of the
-- input.
--
-- Examples:
--
-- > find "::" ""
-- > ==> ("", [])
-- > find "/" "a/b/c/d"
-- > ==> ("a", [("/b","/b/c/d"), ("/c","/c/d"), ("/d","/d")])
--
-- In (unlikely) bad cases, this function's time complexity degrades
-- towards /O(n*m)/.
find :: Text -> Text -> (Text, [(Text, Text)])
find pat src@(Text arr off len)
    | null pat  = emptyError "find"
    | otherwise = case indices pat src of
                    []     -> (src, [])
                    (x:xs) -> (chunk 0 x, go x xs)
  where
    go !s (x:xs) = (chunk s (x-s), chunk s (len-s)) : go x xs
    go  s _      = let c = chunk s (len-s)
                   in [(c,c)]
    chunk !n !l  = textP arr (n+off) l
{-# INLINE find #-}

-------------------------------------------------------------------------------
-- ** Indexing 'Text's

-- $index
--
-- If you think of a 'Text' value as an array of 'Char' values (which
-- it is not), you run the risk of writing inefficient code.
--
-- An idiom that is common in some languages is to find the numeric
-- offset of a character or substring, then use that number to split
-- or trim the searched string.  With a 'Text' value, this approach
-- would require two /O(n)/ operations: one to perform the search, and
-- one to operate from wherever the search ended.
--
-- For example, suppose you have a string that you want to split on
-- the substring @\"::\"@, such as @\"foo::bar::quux\"@. Instead of
-- searching for the index of @\"::\"@ and taking the substrings
-- before and after that index, you would instead use @find \"::\"@.

-- | /O(n)/ 'Text' index (subscript) operator, starting from 0.
index :: Text -> Int -> Char
index t n = S.index (stream t) n
{-# INLINE index #-}

-- | /O(n)/ The 'findIndex' function takes a predicate and a 'Text'
-- and returns the index of the first element in the 'Text' satisfying
-- the predicate. Subject to fusion.
findIndex :: (Char -> Bool) -> Text -> Maybe Int
findIndex p t = S.findIndex p (stream t)
{-# INLINE findIndex #-}

-- | /O(n+m)/ The 'count' function returns the number of times the
-- query string appears in the given 'Text'. An empty query string is
-- invalid, and will cause an error to be raised.
--
-- In (unlikely) bad cases, this function's time complexity degrades
-- towards /O(n*m)/.
count :: Text -> Text -> Int
count pat src
    | null pat        = emptyError "count"
    | isSingleton pat = countChar (unsafeHead pat) src
    | otherwise       = L.length (indices pat src)
{-# INLINE [1] count #-}

{-# RULES
"TEXT count/singleton -> countChar" [~1] forall c t.
    count (singleton c) t = countChar c t
  #-}

-- | /O(n)/ The 'countChar' function returns the number of times the
-- query element appears in the given 'Text'. Subject to fusion.
countChar :: Char -> Text -> Int
countChar c t = S.countChar c (stream t)
{-# INLINE countChar #-}

-------------------------------------------------------------------------------
-- * Zipping

-- | /O(n)/ 'zip' takes two 'Text's and returns a list of
-- corresponding pairs of bytes. If one input 'Text' is short,
-- excess elements of the longer 'Text' are discarded. This is
-- equivalent to a pair of 'unpack' operations.
zip :: Text -> Text -> [(Char,Char)]
zip a b = S.unstreamList $ S.zipWith (,) (stream a) (stream b)
{-# INLINE [0] zip #-}

-- | /O(n)/ 'zipWith' generalises 'zip' by zipping with the function
-- given as the first argument, instead of a tupling function.
zipWith :: (Char -> Char -> Char) -> Text -> Text -> Text
zipWith f t1 t2 = unstream (S.zipWith f (stream t1) (stream t2))
{-# INLINE [0] zipWith #-}

-- | /O(n)/ Breaks a 'Text' up into a list of words, delimited by 'Char's
-- representing white space.
words :: Text -> [Text]
words t@(Text arr off len) = loop 0 0
  where
    loop !start !n
        | n >= len = if start == n
                     then []
                     else [Text arr (start+off) (n-start)]
        | isSpace c =
            if start == n
            then loop (start+1) (start+1)
            else Text arr (start+off) (n-start) : loop (n+d) (n+d)
        | otherwise = loop start (n+d)
        where (c,d) = iter t n
{-# INLINE words #-}

-- | /O(n)/ Breaks a 'Text' up into a list of 'Text's at
-- newline 'Char's. The resulting strings do not contain newlines.
lines :: Text -> [Text]
lines ps | null ps   = []
         | otherwise = h : if null t
                           then []
                           else lines (unsafeTail t)
    where (h,t) = spanBy (/= '\n') ps
{-# INLINE lines #-}

{-
-- | /O(n)/ Portably breaks a 'Text' up into a list of 'Text's at line
-- boundaries.
--
-- A line boundary is considered to be either a line feed, a carriage
-- return immediately followed by a line feed, or a carriage return.
-- This accounts for both Unix and Windows line ending conventions,
-- and for the old convention used on Mac OS 9 and earlier.
lines' :: Text -> [Text]
lines' ps | null ps   = []
          | otherwise = h : case uncons t of
                              Nothing -> []
                              Just (c,t')
                                  | c == '\n' -> lines t'
                                  | c == '\r' -> case uncons t' of
                                                   Just ('\n',t'') -> lines t''
                                                   _               -> lines t'
    where (h,t)    = span notEOL ps
          notEOL c = c /= '\n' && c /= '\r'
{-# INLINE lines' #-}
-}

-- | /O(n)/ Joins lines, after appending a terminating newline to
-- each.
unlines :: [Text] -> Text
unlines = concat . L.map (`snoc` '\n')
{-# INLINE unlines #-}

-- | /O(n)/ Joins words using single space characters.
unwords :: [Text] -> Text
unwords = intercalate (singleton ' ')
{-# INLINE unwords #-}

-- | /O(n)/ The 'isPrefixOf' function takes two 'Text's and returns
-- 'True' iff the first is a prefix of the second.  This function is
-- subject to fusion.
isPrefixOf :: Text -> Text -> Bool
isPrefixOf a@(Text _ _ alen) b@(Text _ _ blen) =
    alen <= blen && S.isPrefixOf (stream a) (stream b)
{-# INLINE [1] isPrefixOf #-}

{-# RULES
"TEXT isPrefixOf -> fused" [~1] forall s t.
    isPrefixOf s t = S.isPrefixOf (stream s) (stream t)
"TEXT isPrefixOf -> unfused" [1] forall s t.
    S.isPrefixOf (stream s) (stream t) = isPrefixOf s t
  #-}

-- | /O(n)/ The 'isSuffixOf' function takes two 'Text's and returns
-- 'True' iff the first is a suffix of the second.
isSuffixOf :: Text -> Text -> Bool
isSuffixOf a@(Text _aarr _aoff alen) b@(Text barr boff blen) =
    d >= 0 && a == b'
  where d              = blen - alen
        b' | d == 0    = b
           | otherwise = Text barr (boff+d) alen
{-# INLINE isSuffixOf #-}

-- | /O(n+m)/ The 'isInfixOf' function takes two 'Text's and returns
-- 'True' iff the first is contained, wholly and intact, anywhere
-- within the second.
--
-- In (unlikely) bad cases, this function's time complexity degrades
-- towards /O(n*m)/.
isInfixOf :: Text -> Text -> Bool
isInfixOf needle haystack
    | null needle        = True
    | isSingleton needle = S.elem (unsafeHead needle) . S.stream $ haystack
    | otherwise          = not . L.null . indices needle $ haystack
{-# INLINE [1] isInfixOf #-}

{-# RULES
"TEXT isInfixOf/singleton -> S.elem/S.stream" [~1] forall n h.
    isInfixOf (singleton n) h = S.elem n (S.stream h)
  #-}

emptyError :: String -> a
emptyError fun = P.error ("Data.Text." ++ fun ++ ": empty input")
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.