/usr/lib/hugs/packages/haskell-src/Language/Haskell/Lexer.hs is in libhugs-haskell-src-bundled 98.200609.21-5.3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | -- #hide
-----------------------------------------------------------------------------
-- |
-- Module : Language.Haskell.Lexer
-- Copyright : (c) The GHC Team, 1997-2000
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : portable
--
-- Lexer for Haskell.
--
-----------------------------------------------------------------------------
-- ToDo: Introduce different tokens for decimal, octal and hexadecimal (?)
-- ToDo: FloatTok should have three parts (integer part, fraction, exponent) (?)
-- ToDo: Use a lexical analyser generator (lx?)
module Language.Haskell.Lexer (Token(..), lexer) where
import Language.Haskell.ParseMonad
import Data.Char (isAlpha, isLower, isUpper, toLower,
isDigit, isHexDigit, isOctDigit, isSpace,
ord, chr, digitToInt)
import Data.Ratio
data Token
= VarId String
| QVarId (String,String)
| ConId String
| QConId (String,String)
| VarSym String
| ConSym String
| QVarSym (String,String)
| QConSym (String,String)
| IntTok Integer
| FloatTok Rational
| Character Char
| StringTok String
-- Symbols
| LeftParen
| RightParen
| SemiColon
| LeftCurly
| RightCurly
| VRightCurly -- a virtual close brace
| LeftSquare
| RightSquare
| Comma
| Underscore
| BackQuote
-- Reserved operators
| DotDot
| Colon
| DoubleColon
| Equals
| Backslash
| Bar
| LeftArrow
| RightArrow
| At
| Tilde
| DoubleArrow
| Minus
| Exclamation
-- Reserved Ids
| KW_As
| KW_Case
| KW_Class
| KW_Data
| KW_Default
| KW_Deriving
| KW_Do
| KW_Else
| KW_Hiding
| KW_If
| KW_Import
| KW_In
| KW_Infix
| KW_InfixL
| KW_InfixR
| KW_Instance
| KW_Let
| KW_Module
| KW_NewType
| KW_Of
| KW_Then
| KW_Type
| KW_Where
| KW_Qualified
| EOF
deriving (Eq,Show)
reserved_ops :: [(String,Token)]
reserved_ops = [
( "..", DotDot ),
( ":", Colon ),
( "::", DoubleColon ),
( "=", Equals ),
( "\\", Backslash ),
( "|", Bar ),
( "<-", LeftArrow ),
( "->", RightArrow ),
( "@", At ),
( "~", Tilde ),
( "=>", DoubleArrow )
]
special_varops :: [(String,Token)]
special_varops = [
( "-", Minus ), --ToDo: shouldn't be here
( "!", Exclamation ) --ditto
]
reserved_ids :: [(String,Token)]
reserved_ids = [
( "_", Underscore ),
( "case", KW_Case ),
( "class", KW_Class ),
( "data", KW_Data ),
( "default", KW_Default ),
( "deriving", KW_Deriving ),
( "do", KW_Do ),
( "else", KW_Else ),
( "if", KW_If ),
( "import", KW_Import ),
( "in", KW_In ),
( "infix", KW_Infix ),
( "infixl", KW_InfixL ),
( "infixr", KW_InfixR ),
( "instance", KW_Instance ),
( "let", KW_Let ),
( "module", KW_Module ),
( "newtype", KW_NewType ),
( "of", KW_Of ),
( "then", KW_Then ),
( "type", KW_Type ),
( "where", KW_Where )
]
special_varids :: [(String,Token)]
special_varids = [
( "as", KW_As ),
( "qualified", KW_Qualified ),
( "hiding", KW_Hiding )
]
isIdent, isSymbol :: Char -> Bool
isIdent c = isAlpha c || isDigit c || c == '\'' || c == '_'
isSymbol c = elem c ":!#$%&*+./<=>?@\\^|-~"
matchChar :: Char -> String -> Lex a ()
matchChar c msg = do
s <- getInput
if null s || head s /= c then fail msg else discard 1
-- The top-level lexer.
-- We need to know whether we are at the beginning of the line to decide
-- whether to insert layout tokens.
lexer :: (Token -> P a) -> P a
lexer = runL $ do
bol <- checkBOL
bol <- lexWhiteSpace bol
startToken
if bol then lexBOL else lexToken
lexWhiteSpace :: Bool -> Lex a Bool
lexWhiteSpace bol = do
s <- getInput
case s of
'{':'-':_ -> do
discard 2
bol <- lexNestedComment bol
lexWhiteSpace bol
'-':'-':rest | all (== '-') (takeWhile isSymbol rest) -> do
lexWhile (== '-')
lexWhile (/= '\n')
s' <- getInput
case s' of
[] -> fail "Unterminated end-of-line comment"
_ -> do
lexNewline
lexWhiteSpace True
'\n':_ -> do
lexNewline
lexWhiteSpace True
'\t':_ -> do
lexTab
lexWhiteSpace bol
c:_ | isSpace c -> do
discard 1
lexWhiteSpace bol
_ -> return bol
lexNestedComment :: Bool -> Lex a Bool
lexNestedComment bol = do
s <- getInput
case s of
'-':'}':_ -> discard 2 >> return bol
'{':'-':_ -> do
discard 2
bol <- lexNestedComment bol -- rest of the subcomment
lexNestedComment bol -- rest of this comment
'\t':_ -> lexTab >> lexNestedComment bol
'\n':_ -> lexNewline >> lexNestedComment True
_:_ -> discard 1 >> lexNestedComment bol
[] -> fail "Unterminated nested comment"
-- When we are lexing the first token of a line, check whether we need to
-- insert virtual semicolons or close braces due to layout.
lexBOL :: Lex a Token
lexBOL = do
pos <- getOffside
case pos of
LT -> do
-- trace "layout: inserting '}'\n" $
-- Set col to 0, indicating that we're still at the
-- beginning of the line, in case we need a semi-colon too.
-- Also pop the context here, so that we don't insert
-- another close brace before the parser can pop it.
setBOL
popContextL "lexBOL"
return VRightCurly
EQ ->
-- trace "layout: inserting ';'\n" $
return SemiColon
GT ->
lexToken
lexToken :: Lex a Token
lexToken = do
s <- getInput
case s of
[] -> return EOF
'0':c:d:_ | toLower c == 'o' && isOctDigit d -> do
discard 2
n <- lexOctal
return (IntTok n)
| toLower c == 'x' && isHexDigit d -> do
discard 2
n <- lexHexadecimal
return (IntTok n)
c:_ | isDigit c -> lexDecimalOrFloat
| isUpper c -> lexConIdOrQual ""
| isLower c || c == '_' -> do
ident <- lexWhile isIdent
return $ case lookup ident (reserved_ids ++ special_varids) of
Just keyword -> keyword
Nothing -> VarId ident
| isSymbol c -> do
sym <- lexWhile isSymbol
return $ case lookup sym (reserved_ops ++ special_varops) of
Just t -> t
Nothing -> case c of
':' -> ConSym sym
_ -> VarSym sym
| otherwise -> do
discard 1
case c of
-- First the special symbols
'(' -> return LeftParen
')' -> return RightParen
',' -> return Comma
';' -> return SemiColon
'[' -> return LeftSquare
']' -> return RightSquare
'`' -> return BackQuote
'{' -> do
pushContextL NoLayout
return LeftCurly
'}' -> do
popContextL "lexToken"
return RightCurly
'\'' -> do
c2 <- lexChar
matchChar '\'' "Improperly terminated character constant"
return (Character c2)
'"' -> lexString
_ -> fail ("Illegal character \'" ++ show c ++ "\'\n")
lexDecimalOrFloat :: Lex a Token
lexDecimalOrFloat = do
ds <- lexWhile isDigit
rest <- getInput
case rest of
('.':d:_) | isDigit d -> do
discard 1
frac <- lexWhile isDigit
let num = parseInteger 10 (ds ++ frac)
decimals = toInteger (length frac)
exponent <- do
rest2 <- getInput
case rest2 of
'e':_ -> lexExponent
'E':_ -> lexExponent
_ -> return 0
return (FloatTok ((num%1) * 10^^(exponent - decimals)))
e:_ | toLower e == 'e' -> do
exponent <- lexExponent
return (FloatTok ((parseInteger 10 ds%1) * 10^^exponent))
_ -> return (IntTok (parseInteger 10 ds))
where
lexExponent :: Lex a Integer
lexExponent = do
discard 1 -- 'e' or 'E'
r <- getInput
case r of
'+':d:_ | isDigit d -> do
discard 1
lexDecimal
'-':d:_ | isDigit d -> do
discard 1
n <- lexDecimal
return (negate n)
d:_ | isDigit d -> lexDecimal
_ -> fail "Float with missing exponent"
lexConIdOrQual :: String -> Lex a Token
lexConIdOrQual qual = do
con <- lexWhile isIdent
let conid | null qual = ConId con
| otherwise = QConId (qual,con)
qual' | null qual = con
| otherwise = qual ++ '.':con
just_a_conid <- alternative (return conid)
rest <- getInput
case rest of
'.':c:_
| isLower c || c == '_' -> do -- qualified varid?
discard 1
ident <- lexWhile isIdent
case lookup ident reserved_ids of
-- cannot qualify a reserved word
Just _ -> just_a_conid
Nothing -> return (QVarId (qual', ident))
| isUpper c -> do -- qualified conid?
discard 1
lexConIdOrQual qual'
| isSymbol c -> do -- qualified symbol?
discard 1
sym <- lexWhile isSymbol
case lookup sym reserved_ops of
-- cannot qualify a reserved operator
Just _ -> just_a_conid
Nothing -> return $ case c of
':' -> QConSym (qual', sym)
_ -> QVarSym (qual', sym)
_ -> return conid -- not a qualified thing
lexChar :: Lex a Char
lexChar = do
r <- getInput
case r of
'\\':_ -> lexEscape
c:_ -> discard 1 >> return c
[] -> fail "Incomplete character constant"
lexString :: Lex a Token
lexString = loop ""
where
loop s = do
r <- getInput
case r of
'\\':'&':_ -> do
discard 2
loop s
'\\':c:_ | isSpace c -> do
discard 1
lexWhiteChars
matchChar '\\' "Illegal character in string gap"
loop s
| otherwise -> do
ce <- lexEscape
loop (ce:s)
'"':_ -> do
discard 1
return (StringTok (reverse s))
c:_ -> do
discard 1
loop (c:s)
[] -> fail "Improperly terminated string"
lexWhiteChars :: Lex a ()
lexWhiteChars = do
s <- getInput
case s of
'\n':_ -> do
lexNewline
lexWhiteChars
'\t':_ -> do
lexTab
lexWhiteChars
c:_ | isSpace c -> do
discard 1
lexWhiteChars
_ -> return ()
lexEscape :: Lex a Char
lexEscape = do
discard 1
r <- getInput
case r of
-- Production charesc from section B.2 (Note: \& is handled by caller)
'a':_ -> discard 1 >> return '\a'
'b':_ -> discard 1 >> return '\b'
'f':_ -> discard 1 >> return '\f'
'n':_ -> discard 1 >> return '\n'
'r':_ -> discard 1 >> return '\r'
't':_ -> discard 1 >> return '\t'
'v':_ -> discard 1 >> return '\v'
'\\':_ -> discard 1 >> return '\\'
'"':_ -> discard 1 >> return '\"'
'\'':_ -> discard 1 >> return '\''
-- Production ascii from section B.2
'^':c:_ -> discard 2 >> cntrl c
'N':'U':'L':_ -> discard 3 >> return '\NUL'
'S':'O':'H':_ -> discard 3 >> return '\SOH'
'S':'T':'X':_ -> discard 3 >> return '\STX'
'E':'T':'X':_ -> discard 3 >> return '\ETX'
'E':'O':'T':_ -> discard 3 >> return '\EOT'
'E':'N':'Q':_ -> discard 3 >> return '\ENQ'
'A':'C':'K':_ -> discard 3 >> return '\ACK'
'B':'E':'L':_ -> discard 3 >> return '\BEL'
'B':'S':_ -> discard 2 >> return '\BS'
'H':'T':_ -> discard 2 >> return '\HT'
'L':'F':_ -> discard 2 >> return '\LF'
'V':'T':_ -> discard 2 >> return '\VT'
'F':'F':_ -> discard 2 >> return '\FF'
'C':'R':_ -> discard 2 >> return '\CR'
'S':'O':_ -> discard 2 >> return '\SO'
'S':'I':_ -> discard 2 >> return '\SI'
'D':'L':'E':_ -> discard 3 >> return '\DLE'
'D':'C':'1':_ -> discard 3 >> return '\DC1'
'D':'C':'2':_ -> discard 3 >> return '\DC2'
'D':'C':'3':_ -> discard 3 >> return '\DC3'
'D':'C':'4':_ -> discard 3 >> return '\DC4'
'N':'A':'K':_ -> discard 3 >> return '\NAK'
'S':'Y':'N':_ -> discard 3 >> return '\SYN'
'E':'T':'B':_ -> discard 3 >> return '\ETB'
'C':'A':'N':_ -> discard 3 >> return '\CAN'
'E':'M':_ -> discard 2 >> return '\EM'
'S':'U':'B':_ -> discard 3 >> return '\SUB'
'E':'S':'C':_ -> discard 3 >> return '\ESC'
'F':'S':_ -> discard 2 >> return '\FS'
'G':'S':_ -> discard 2 >> return '\GS'
'R':'S':_ -> discard 2 >> return '\RS'
'U':'S':_ -> discard 2 >> return '\US'
'S':'P':_ -> discard 2 >> return '\SP'
'D':'E':'L':_ -> discard 3 >> return '\DEL'
-- Escaped numbers
'o':c:_ | isOctDigit c -> do
discard 1
n <- lexOctal
checkChar n
'x':c:_ | isHexDigit c -> do
discard 1
n <- lexHexadecimal
checkChar n
c:_ | isDigit c -> do
n <- lexDecimal
checkChar n
_ -> fail "Illegal escape sequence"
where
checkChar n | n <= 0x01FFFF = return (chr (fromInteger n))
checkChar _ = fail "Character constant out of range"
-- Production cntrl from section B.2
cntrl :: Char -> Lex a Char
cntrl c | c >= '@' && c <= '_' = return (chr (ord c - ord '@'))
cntrl _ = fail "Illegal control character"
-- assumes at least one octal digit
lexOctal :: Lex a Integer
lexOctal = do
ds <- lexWhile isOctDigit
return (parseInteger 8 ds)
-- assumes at least one hexadecimal digit
lexHexadecimal :: Lex a Integer
lexHexadecimal = do
ds <- lexWhile isHexDigit
return (parseInteger 16 ds)
-- assumes at least one decimal digit
lexDecimal :: Lex a Integer
lexDecimal = do
ds <- lexWhile isDigit
return (parseInteger 10 ds)
-- Stolen from Hugs's Prelude
parseInteger :: Integer -> String -> Integer
parseInteger radix ds =
foldl1 (\n d -> n * radix + d) (map (toInteger . digitToInt) ds)
|