1 # Copyright (c) 2002-2010 International Business Machines Corporation and 2 # others. All Rights Reserved. 3 # 4 # file: line.txt 5 # 6 # Line Breaking Rules 7 # Implement default line breaking as defined by 8 # Unicode Standard Annex #14 Revision 24 for Unicode 6.0 9 # http://www.unicode.org/reports/tr14/ 10 # 11 # TODO: Rule LB 8 remains as it was in Unicode 5.2 12 # This is only because of a limitation of ICU break engine implementation, 13 # not because the older behavior is desirable. 14 15 # 16 # Character Classes defined by TR 14. 17 # 18 19 !!chain; 20 !!LBCMNoChain; 21 22 23 !!lookAheadHardBreak; 24 # 25 # !!lookAheadHardBreak Described here because it is (as yet) undocumented elsewhere 26 # and only used for the line break rules. 27 # 28 # It is used in the implementation of rule LB 10 29 # which says to treat any combining mark that is not attached to a base 30 # character as if it were of class AL (alphabetic). 31 # 32 # The problem occurs in the reverse rules. 33 # 34 # Consider a sequence like, with correct breaks as shown 35 # LF ID CM AL AL 36 # ^ ^ ^ 37 # Then consider the sequence without the initial ID (ideographic) 38 # LF CM AL AL 39 # ^ ^ 40 # Our CM, which in the first example was attached to the ideograph, 41 # is now unattached, becomes an alpha, and joins in with the other 42 # alphas. 43 # 44 # When iterating forwards, these sequences do not present any problems 45 # When iterating backwards, we need to look ahead when encountering 46 # a CM to see whether it attaches to something further on or not. 47 # (Look-ahead in a reverse rule is looking towards the start) 48 # 49 # If the CM is unattached, we need to force a break. 50 # 51 # !!lookAheadHardBreak forces the run time state machine to 52 # stop immediately when a look ahead rule ( '/' operator) matches, 53 # and set the match position to that of the look-ahead operator, 54 # no matter what other rules may be in play at the time. 55 # 56 # See rule LB 19 for an example. 57 # 58 59 $AI = [:LineBreak = Ambiguous:]; 60 $AL = [:LineBreak = Alphabetic:]; 61 $BA = [:LineBreak = Break_After:]; 62 $BB = [:LineBreak = Break_Before:]; 63 $BK = [:LineBreak = Mandatory_Break:]; 64 $B2 = [:LineBreak = Break_Both:]; 65 $CB = [:LineBreak = Contingent_Break:]; 66 $CL = [:LineBreak = Close_Punctuation:]; 67 $CM = [:LineBreak = Combining_Mark:]; 68 $CP = [:LineBreak = Close_Parenthesis:]; 69 $CR = [:LineBreak = Carriage_Return:]; 70 $EX = [:LineBreak = Exclamation:]; 71 $GL = [:LineBreak = Glue:]; 72 $HY = [:LineBreak = Hyphen:]; 73 $H2 = [:LineBreak = H2:]; 74 $H3 = [:LineBreak = H3:]; 75 $ID = [:LineBreak = Ideographic:]; 76 $IN = [:LineBreak = Inseperable:]; 77 $IS = [:LineBreak = Infix_Numeric:]; 78 $JL = [:LineBreak = JL:]; 79 $JV = [:LineBreak = JV:]; 80 $JT = [:LineBreak = JT:]; 81 $LF = [:LineBreak = Line_Feed:]; 82 $NL = [:LineBreak = Next_Line:]; 83 $NS = [:LineBreak = Nonstarter:]; 84 $NU = [:LineBreak = Numeric:]; 85 $OP = [:LineBreak = Open_Punctuation:]; 86 $PO = [:LineBreak = Postfix_Numeric:]; 87 $PR = [:LineBreak = Prefix_Numeric:]; 88 $QU = [:LineBreak = Quotation:]; 89 $SA = [:LineBreak = Complex_Context:]; 90 $SG = [:LineBreak = Surrogate:]; 91 $SP = [:LineBreak = Space:]; 92 $SY = [:LineBreak = Break_Symbols:]; 93 $WJ = [:LineBreak = Word_Joiner:]; 94 $XX = [:LineBreak = Unknown:]; 95 $ZW = [:LineBreak = ZWSpace:]; 96 97 # Dictionary character set, for triggering language-based break engines. Currently 98 # limited to LineBreak=Complex_Context. Note that this set only works in Unicode 99 # 5.0 or later as the definition of Complex_Context was corrected to include all 100 # characters requiring dictionary break. 101 102 $dictionary = [:LineBreak = Complex_Context:]; 103 104 # 105 # Rule LB1. By default, treat AI (characters with ambiguous east Asian width), 106 # SA (South East Asian: Thai, Lao, Khmer) 107 # SG (Unpaired Surrogates) 108 # XX (Unknown, unassigned) 109 # as $AL (Alphabetic) 110 # 111 $ALPlus = [$AL $AI $SA $SG $XX]; 112 113 # 114 # Combining Marks. X $CM* behaves as if it were X. Rule LB6. 115 # 116 $ALcm = $ALPlus $CM*; 117 $BAcm = $BA $CM*; 118 $BBcm = $BB $CM*; 119 $B2cm = $B2 $CM*; 120 $CLcm = $CL $CM*; 121 $CPcm = $CP $CM*; 122 $EXcm = $EX $CM*; 123 $GLcm = $GL $CM*; 124 $HYcm = $HY $CM*; 125 $H2cm = $H2 $CM*; 126 $H3cm = $H3 $CM*; 127 $IDcm = $ID $CM*; 128 $INcm = $IN $CM*; 129 $IScm = $IS $CM*; 130 $JLcm = $JL $CM*; 131 $JVcm = $JV $CM*; 132 $JTcm = $JT $CM*; 133 $NScm = $NS $CM*; 134 $NUcm = $NU $CM*; 135 $OPcm = $OP $CM*; 136 $POcm = $PO $CM*; 137 $PRcm = $PR $CM*; 138 $QUcm = $QU $CM*; 139 $SYcm = $SY $CM*; 140 $WJcm = $WJ $CM*; 141 142 ## ------------------------------------------------- 143 144 !!forward; 145 146 # 147 # Each class of character can stand by itself as an unbroken token, with trailing combining stuff 148 # 149 $ALPlus $CM+; 150 $BA $CM+; 151 $BB $CM+; 152 $B2 $CM+; 153 $CL $CM+; 154 $CP $CM+; 155 $EX $CM+; 156 $GL $CM+; 157 $HY $CM+; 158 $H2 $CM+; 159 $H3 $CM+; 160 $ID $CM+; 161 $IN $CM+; 162 $IS $CM+; 163 $JL $CM+; 164 $JV $CM+; 165 $JT $CM+; 166 $NS $CM+; 167 $NU $CM+; 168 $OP $CM+; 169 $PO $CM+; 170 $PR $CM+; 171 $QU $CM+; 172 $SY $CM+; 173 $WJ $CM+; 174 175 # 176 # CAN_CM is the set of characters that may combine with CM combining chars. 177 # Note that Linebreak UAX 14's concept of a combining char and the rules 178 # for what they can combine with are _very_ different from the rest of Unicode. 179 # 180 # Note that $CM itself is left out of this set. If CM is needed as a base 181 # it must be listed separately in the rule. 182 # 183 $CAN_CM = [^$SP $BK $CR $LF $NL $ZW $CM]; # Bases that can take CMs 184 $CANT_CM = [ $SP $BK $CR $LF $NL $ZW $CM]; # Bases that can't take CMs 185 186 # 187 # AL_FOLLOW set of chars that can unconditionally follow an AL 188 # Needed in rules where stand-alone $CM s are treated as AL. 189 # Chaining is disabled with CM because it causes other failures, 190 # so for this one case we need to manually list out longer sequences. 191 # 192 $AL_FOLLOW_NOCM = [$BK $CR $LF $NL $ZW $SP]; 193 $AL_FOLLOW_CM = [$CL $CP $EX $IS $SY $WJ $GL $OP $QU $BA $HY $NS $IN $NU $ALPlus]; 194 $AL_FOLLOW = [$AL_FOLLOW_NOCM $AL_FOLLOW_CM]; 195 196 197 # 198 # Rule LB 4, 5 Mandatory (Hard) breaks. 199 # 200 $LB4Breaks = [$BK $CR $LF $NL]; 201 $LB4NonBreaks = [^$BK $CR $LF $NL]; 202 $CR $LF {100}; 203 204 # 205 # LB 6 Do not break before hard line breaks. 206 # 207 $LB4NonBreaks? $LB4Breaks {100}; # LB 5 do not break before hard breaks. 208 $CAN_CM $CM* $LB4Breaks {100}; 209 $CM+ $LB4Breaks {100}; 210 211 # LB 7 x SP 212 # x ZW 213 $LB4NonBreaks [$SP $ZW]; 214 $CAN_CM $CM* [$SP $ZW]; 215 $CM+ [$SP $ZW]; 216 217 # 218 # LB 8 Break after zero width space 219 # TODO: ZW SP* <break> 220 # An engine change is required to write the reverse rule for this. 221 # For now, leave the Unicode 5.2 rule, ZW <break> 222 # 223 $LB8Breaks = [$LB4Breaks $ZW]; 224 $LB8NonBreaks = [[$LB4NonBreaks] - [$ZW]]; 225 226 227 # LB 9 Combining marks. X $CM needs to behave like X, where X is not $SP, $BK $CR $LF $NL 228 # $CM not covered by the above needs to behave like $AL 229 # See definition of $CAN_CM. 230 231 $CAN_CM $CM+; # Stick together any combining sequences that don't match other rules. 232 $CM+; 233 234 # 235 # LB 11 Do not break before or after WORD JOINER & related characters. 236 # 237 $CAN_CM $CM* $WJcm; 238 $LB8NonBreaks $WJcm; 239 $CM+ $WJcm; 240 241 $WJcm $CANT_CM; 242 $WJcm $CAN_CM $CM*; 243 244 # 245 # LB 12 Do not break after NBSP and related characters. 246 # GL x 247 # 248 $GLcm $CAN_CM $CM*; 249 $GLcm $CANT_CM; 250 251 # 252 # LB 12a Do not break before NBSP and related characters ... 253 # [^SP BA HY] x GL 254 # 255 [[$LB8NonBreaks] - [$SP $BA $HY]] $CM* $GLcm; 256 $CM+ GLcm; 257 258 259 260 # 261 # LB 13 Don't break before ']' or '!' or ';' or '/', even after spaces. 262 # 263 $LB8NonBreaks $CL; 264 $CAN_CM $CM* $CL; 265 $CM+ $CL; # by rule 10, stand-alone CM behaves as AL 266 267 $LB8NonBreaks $CP; 268 $CAN_CM $CM* $CP; 269 $CM+ $CP; # by rule 10, stand-alone CM behaves as AL 270 271 $LB8NonBreaks $EX; 272 $CAN_CM $CM* $EX; 273 $CM+ $EX; # by rule 10, stand-alone CM behaves as AL 274 275 $LB8NonBreaks $IS; 276 $CAN_CM $CM* $IS; 277 $CM+ $IS; # by rule 10, stand-alone CM behaves as AL 278 279 $LB8NonBreaks $SY; 280 $CAN_CM $CM* $SY; 281 $CM+ $SY; # by rule 10, stand-alone CM behaves as AL 282 283 284 # 285 # LB 14 Do not break after OP, even after spaces 286 # 287 $OPcm $SP* $CAN_CM $CM*; 288 $OPcm $SP* $CANT_CM; 289 290 $OPcm $SP+ $CM+ $AL_FOLLOW?; # by rule 10, stand-alone CM behaves as AL 291 292 # LB 15 293 $QUcm $SP* $OPcm; 294 295 # LB 16 296 ($CLcm | $CPcm) $SP* $NScm; 297 298 # LB 17 299 $B2cm $SP* $B2cm; 300 301 # 302 # LB 18 Break after spaces. 303 # 304 $LB18NonBreaks = [$LB8NonBreaks - [$SP]]; 305 $LB18Breaks = [$LB8Breaks $SP]; 306 307 308 # LB 19 309 # x QU 310 $LB18NonBreaks $CM* $QUcm; 311 $CM+ $QUcm; 312 313 # QU x 314 $QUcm .?; 315 $QUcm $LB18NonBreaks $CM*; # Don't let a combining mark go onto $CR, $BK, etc. 316 # TODO: I don't think this rule is needed. 317 318 319 # LB 20 320 # <break> $CB 321 # $CB <break> 322 323 $LB20NonBreaks = [$LB18NonBreaks - $CB]; 324 325 # LB 21 x (BA | HY | NS) 326 # BB x 327 # 328 $LB20NonBreaks $CM* ($BAcm | $HYcm | $NScm); 329 330 $BBcm [^$CB]; # $BB x 331 $BBcm $LB20NonBreaks $CM*; 332 333 # LB 22 334 $ALcm $INcm; 335 $CM+ $INcm; # by rule 10, any otherwise unattached CM behaves as AL 336 $IDcm $INcm; 337 $INcm $INcm; 338 $NUcm $INcm; 339 340 341 # $LB 23 342 $IDcm $POcm; 343 $ALcm $NUcm; # includes $LB19 344 $CM+ $NUcm; # Rule 10, any otherwise unattached CM behaves as AL 345 $NUcm $ALcm; 346 347 # 348 # LB 24 349 # 350 $PRcm $IDcm; 351 $PRcm $ALcm; 352 $POcm $ALcm; 353 354 # 355 # LB 25 Numbers. 356 # 357 ($PRcm | $POcm)? ($OPcm | $HYcm)? $NUcm ($NUcm | $SYcm | $IScm)* ($CLcm | $CPcm)? ($PRcm | $POcm)?; 358 359 # LB 26 Do not break a Korean syllable 360 # 361 $JLcm ($JLcm | $JVcm | $H2cm | $H3cm); 362 ($JVcm | $H2cm) ($JVcm | $JTcm); 363 ($JTcm | $H3cm) $JTcm; 364 365 # LB 27 Treat korean Syllable Block the same as ID (don't break it) 366 ($JLcm | $JVcm | $JTcm | $H2cm | $H3cm) $INcm; 367 ($JLcm | $JVcm | $JTcm | $H2cm | $H3cm) $POcm; 368 $PRcm ($JLcm | $JVcm | $JTcm | $H2cm | $H3cm); 369 370 371 # LB 28 Do not break between alphabetics 372 # 373 $ALcm $ALcm; 374 $CM+ $ALcm; # The $CM+ is from rule 10, an unattached CM is treated as AL 375 376 # LB 29 377 $IScm $ALcm; 378 379 # LB 30 380 ($ALcm | $NUcm) $OPcm; 381 $CM+ $OPcm; # The $CM+ is from rule 10, an unattached CM is treated as AL. 382 $CPcm ($ALcm | $NUcm); 383 384 385 # 386 # Reverse Rules. 387 # 388 ## ------------------------------------------------- 389 390 !!reverse; 391 392 $CM+ $ALPlus; 393 $CM+ $BA; 394 $CM+ $BB; 395 $CM+ $B2; 396 $CM+ $CL; 397 $CM+ $CP; 398 $CM+ $EX; 399 $CM+ $GL; 400 $CM+ $HY; 401 $CM+ $H2; 402 $CM+ $H3; 403 $CM+ $ID; 404 $CM+ $IN; 405 $CM+ $IS; 406 $CM+ $JL; 407 $CM+ $JV; 408 $CM+ $JT; 409 $CM+ $NS; 410 $CM+ $NU; 411 $CM+ $OP; 412 $CM+ $PO; 413 $CM+ $PR; 414 $CM+ $QU; 415 $CM+ $SY; 416 $CM+ $WJ; 417 $CM+; 418 419 420 # 421 # Sequences of the form (shown forwards) 422 # [CANT_CM] <break> [CM] [whatever] 423 # The CM needs to behave as an AL 424 # 425 $AL_FOLLOW $CM+ / ( 426 [$BK $CR $LF $NL $ZW {eof}] | 427 $SP+ $CM+ $SP | 428 $SP+ $CM* ([^$OP $CM $SP] | [$AL {eof}])); # if LB 14 will match, need to surpress this break. 429 # LB14 says OP SP* x . 430 # becomes OP SP* x AL 431 # becomes OP SP* x CM+ AL_FOLLOW 432 # 433 # Further note: the $AL in [$AL {eof}] is only to work around 434 # a rule compiler bug which complains about 435 # empty sets otherwise. 436 437 # 438 # Sequences of the form (shown forwards) 439 # [CANT_CM] <break> [CM] <break> [PR] 440 # The CM needs to behave as an AL 441 # This rule is concerned about getting the second of the two <breaks> in place. 442 # 443 444 [$PR ] / $CM+ [$BK $CR $LF $NL $ZW $SP {eof}]; 445 446 447 448 # LB 4, 5, 5 449 450 $LB4Breaks [$LB4NonBreaks-$CM]; 451 $LB4Breaks $CM+ $CAN_CM; 452 $LF $CR; 453 454 455 # LB 7 x SP 456 # x ZW 457 [$SP $ZW] [$LB4NonBreaks-$CM]; 458 [$SP $ZW] $CM+ $CAN_CM; 459 460 # LB 8 ZW SP* <break> 461 # TODO: to implement this, we need more than one look-ahead hard break in play at a time. 462 # Requires an engine enhancement. 463 # / $SP* $ZW 464 465 # LB 9,10 Combining marks. 466 # X $CM needs to behave like X, where X is not $SP or controls. 467 # $CM not covered by the above needs to behave like $AL 468 # Stick together any combining sequences that don't match other rules. 469 $CM+ $CAN_CM; 470 471 472 # LB 11 473 $CM* $WJ $CM* $CAN_CM; 474 $CM* $WJ [$LB8NonBreaks-$CM]; 475 476 $CANT_CM $CM* $WJ; 477 $CM* $CAN_CM $CM* $WJ; 478 479 # LB 12a 480 # [^SP BA HY] x GL 481 # 482 $CM* $GL $CM* [$LB8NonBreaks-[$CM $SP $BA $HY]]; 483 484 # LB 12 485 # GL x 486 # 487 $CANT_CM $CM* $GL; 488 $CM* $CAN_CM $CM* $GL; 489 490 491 # LB 13 492 $CL $CM+ $CAN_CM; 493 $CP $CM+ $CAN_CM; 494 $EX $CM+ $CAN_CM; 495 $IS $CM+ $CAN_CM; 496 $SY $CM+ $CAN_CM; 497 498 $CL [$LB8NonBreaks-$CM]; 499 $CP [$LB8NonBreaks-$CM]; 500 $EX [$LB8NonBreaks-$CM]; 501 $IS [$LB8NonBreaks-$CM]; 502 $SY [$LB8NonBreaks-$CM]; 503 504 # Rule 13 & 14 taken together for an edge case. 505 # Match this, shown forward 506 # OP SP+ ($CM+ behaving as $AL) (CL | CP | EX | IS | IY) 507 # This really wants to chain at the $CM+ (which is acting as an $AL) 508 # except for $CM chaining being disabled. 509 [$CL $CP $EX $IS $SY] $CM+ $SP+ $CM* $OP; 510 511 # LB 14 OP SP* x 512 # 513 $CM* $CAN_CM $SP* $CM* $OP; 514 $CANT_CM $SP* $CM* $OP; 515 $AL_FOLLOW? $CM+ $SP $SP* $CM* $OP; # by LB 10, behaves like $AL_FOLLOW? $AL $SP* $CM* $OP 516 517 $AL_FOLLOW_NOCM $CM+ $SP+ $CM* $OP; 518 $CM* $AL_FOLLOW_CM $CM+ $SP+ $CM* $OP; 519 $SY $CM $SP+ $OP; # TODO: Experiment. Remove. 520 521 522 523 # LB 15 524 $CM* $OP $SP* $CM* $QU; 525 526 # LB 16 527 $CM* $NS $SP* $CM* ($CL | $CP); 528 529 # LB 17 530 $CM* $B2 $SP* $CM* $B2; 531 532 # LB 18 break after spaces 533 # Nothing explicit needed here. 534 535 536 # 537 # LB 19 538 # 539 $CM* $QU $CM* $CAN_CM; # . x QU 540 $CM* $QU $LB18NonBreaks; 541 542 543 $CM* $CAN_CM $CM* $QU; # QU x . 544 $CANT_CM $CM* $QU; 545 546 # 547 # LB 20 Break before and after CB. 548 # nothing needed here. 549 # 550 551 # LB 21 552 $CM* ($BA | $HY | $NS) $CM* [$LB20NonBreaks-$CM]; # . x (BA | HY | NS) 553 554 $CM* [$LB20NonBreaks-$CM] $CM* $BB; # BB x . 555 [^$CB] $CM* $BB; # 556 557 558 559 # LB 22 560 $CM* $IN $CM* $ALPlus; 561 $CM* $IN $CM* $ID; 562 $CM* $IN $CM* $IN; 563 $CM* $IN $CM* $NU; 564 565 # LB 23 566 $CM* $PO $CM* $ID; 567 $CM* $NU $CM* $ALPlus; 568 $CM* $ALPlus $CM* $NU; 569 570 # LB 24 571 $CM* $ID $CM* $PR; 572 $CM* $ALPlus $CM* $PR; 573 $CM* $ALPlus $CM* $PO; 574 575 576 # LB 25 577 ($CM* ($PR | $PO))? ($CM* ($CL | $CP))? ($CM* ($NU | $IS | $SY))* $CM* $NU ($CM* ($OP | $HY))? ($CM* ($PR | $PO))?; 578 579 # LB 26 580 $CM* ($H3 | $H2 | $JV | $JL) $CM* $JL; 581 $CM* ($JT | $JV) $CM* ($H2 | $JV); 582 $CM* $JT $CM* ($H3 | $JT); 583 584 # LB 27 585 $CM* $IN $CM* ($H3 | $H2 | $JT | $JV | $JL); 586 $CM* $PO $CM* ($H3 | $H2 | $JT | $JV | $JL); 587 $CM* ($H3 | $H2 | $JT | $JV | $JL) $CM* $PR; 588 589 # LB 28 590 $CM* $ALPlus $CM* $ALPlus; 591 592 593 # LB 29 594 $CM* $ALPlus $CM* $IS; 595 596 # LB 30 597 $CM* $OP $CM* ($ALPlus | $NU); 598 $CM* ($ALPlus | $NU) $CM* $CP; 599 600 601 ## ------------------------------------------------- 602 603 !!safe_reverse; 604 605 # LB 9 606 $CM+ [^$CM $BK $CR $LF $NL $ZW $SP]; 607 $CM+ $SP / .; 608 609 # LB 14 610 $SP+ $CM* $OP; 611 612 # LB 15 613 $SP+ $CM* $QU; 614 615 # LB 16 616 $SP+ $CM* ($CL | $CP); 617 618 # LB 17 619 $SP+ $CM* $B2; 620 621 # LB 25 622 ($CM* ($IS | $SY))+ $CM* $NU; 623 ($CL | $CP) $CM* ($NU | $IS | $SY); 624 625 # For dictionary-based break 626 $dictionary $dictionary; 627 628 ## ------------------------------------------------- 629 630 !!safe_forward; 631 632 # Skip forward over all character classes that are involved in 633 # rules containing patterns with possibly more than one char 634 # of context. 635 # 636 # It might be slightly more efficient to have specific rules 637 # instead of one generic one, but only if we could 638 # turn off rule chaining. We don't want to move more 639 # than necessary. 640 # 641 [$CM $OP $QU $CL $CP $B2 $PR $HY $SP $dictionary]+ [^$CM $OP $QU $CL $CP $B2 $PR $HY $dictionary]; 642 $dictionary $dictionary; 643 644
