aboutsummaryrefslogtreecommitdiff
path: root/src/HsLexer.lhs
blob: ac5fa9ae6b5707c17e74f54d0c754fad879c7691 (plain) (blame)
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
-----------------------------------------------------------------------------
-- $Id: HsLexer.lhs,v 1.3 2002/04/24 15:12:41 simonmar Exp $
--
-- (c) The GHC Team, 1997-2000
--
-- Lexer for Haskell.
--
-----------------------------------------------------------------------------

ToDo: Parsing floats is a *real* hack...
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?)

\begin{code}
module HsLexer (Token(..), lexer, parseError,isSymbol) where

import HsParseMonad
import HsParseUtils
import HsSyn(SrcLoc(..))

import Numeric	( readHex, readOct )
import Char
\end{code}

\begin{code}
data Token 
        = VarId String
        | QVarId (String,String)
	| ConId String
        | QConId (String,String)
        | VarSym String
        | ConSym String
        | QVarSym (String,String)
        | QConSym (String,String)

-- Literals

	| IntTok     Integer
        | FloatTok   String
	| Character  Char
        | StringTok  String
	| PrimChar   Char		-- GHC extension
	| PrimInt    Integer		-- GHC extension
        | PrimString String		-- GHC extension
	| PrimFloat  String		-- GHC extension
	| PrimDouble String		-- GHC extension

-- Symbols

	| LeftParen
	| RightParen
	| SemiColon
        | LeftCurly
        | RightCurly
        | VRightCurly			-- a virtual close brace
        | LeftSquare
        | RightSquare
	| Comma
        | Underscore
        | BackQuote
	| LeftUT			-- GHC Extension: (#
	| RightUT			-- GHC Extension: #)
	
-- Documentation annotations

	| DocCommentNext String		-- something beginning '-- |'
	| DocCommentPrev String		-- something beginning '-- ^'
	| DocCommentNamed String	-- something beginning '-- @'
	| DocSection Int String		-- a section heading

-- Reserved operators

	| Dot				-- GHC extension
	| DotDot
	| DoubleColon
	| Equals
	| Backslash
	| Bar
	| LeftArrow
	| RightArrow
	| At
	| Tilde
	| DoubleArrow
	| Minus
	| Exclamation

-- Reserved Ids

	| KW_As
	| KW_Case
	| KW_CCall
	| KW_Class
	| KW_Data
	| KW_Default
	| KW_Deriving
	| KW_Do
	| KW_DotNet
	| KW_Else
	| KW_Export
	| KW_Forall
	| KW_Foreign
        | 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_Safe
	| KW_StdCall
	| KW_Then
	| KW_ThreadSafe
	| KW_Type
	| KW_Unsafe
	| KW_Where    
	| KW_Qualified

        | EOF
        deriving (Eq,Show)

reserved_ops :: [(String,Token)]
reserved_ops = [
 ( ".",  Dot ),				-- GHC extension
 ( "..", DotDot ),    
 ( "::", DoubleColon ),
 ( "=",  Equals ),    
 ( "\\", Backslash ), 
 ( "|",  Bar ),       
 ( "<-", LeftArrow ), 
 ( "->", RightArrow ),
 ( "@",  At ),        
 ( "~",  Tilde ),     
 ( "=>", DoubleArrow ),
 ( "-",  Minus ),			--ToDo: shouldn't be here
 ( "!",  Exclamation )		--ditto
 ]

reserved_ids :: [(String,Token)]
reserved_ids = [
 ( "_",         Underscore ),
 ( "case",      KW_Case ),     
 ( "ccall",     KW_CCall ),
 ( "class",     KW_Class ),    
 ( "data",      KW_Data ),     
 ( "default",   KW_Default ),  
 ( "deriving",  KW_Deriving ), 
 ( "do",        KW_Do ),       
 ( "dotnet",    KW_DotNet ),       
 ( "else",      KW_Else ),     
 ( "export",    KW_Export ),     
 ( "forall",    KW_Forall ),     
 ( "foreign",   KW_Foreign ),     
 ( "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 ),       
 ( "safe", 	KW_Safe ),     
 ( "then", 	KW_Then ),     
 ( "threadsafe",KW_ThreadSafe ),     
 ( "type", 	KW_Type ),     
 ( "unsafe", 	KW_Unsafe ),
 ( "where", 	KW_Where ),    
 ( "as", 	KW_As ),       
 ( "qualified", KW_Qualified ),
 ( "hiding", 	KW_Hiding )
 ]

isIdent  c = isAlpha c || isDigit c || c == '\'' || c == '_'
isSymbol c = elem c ":!#$%&*+./<=>?@\\^|-~"
isWhite  c = elem c " \n\r\t\v\f"

tAB_LENGTH = 8 :: Int

-- The source location, (y,x), is the coordinates of the previous token.
-- col is the current column in the source file.  If col is 0, we are
-- somewhere at the beginning of the line before the first token.

-- Setting col to 0 is used in two places: just after emitting a virtual
-- close brace due to layout, so that next time through we check whether
-- we also need to emit a semi-colon, and at the beginning of the file,
-- to kick off the lexer.


lexer :: (Token -> P a) -> P a
lexer cont input (SrcLoc _ x) y col =
        if col == 0
           then tab y x True  input
           else tab y col False input -- throw away old x
  where
   	-- move past whitespace and comments
        tab y x bol [] = 
        	cont EOF [] (SrcLoc y x) col y
        tab y x bol ('\t':s) =
        	tab y (nextTab x) bol s
        tab y x bol ('\n':s) =
                newLine cont s y
        tab y x bol ('-':'-':s) | not (doc s) =
        	newLine cont (drop 1 (dropWhile (/= '\n') s)) y
        tab y x bol ('{':'-':s) = nestedComment tab y x bol s
        tab y x bol (c:s)
        	| isWhite c = tab y (x+1) bol s
        	| otherwise = 
        		if bol 	then lexBOL   cont (c:s) (SrcLoc y x) y x
        			else lexToken cont (c:s) (SrcLoc y x) y x

	newLine cont s y =  tab (y+1) 1 True s

	doc (' ':'|':_) = True
	doc (' ':'/':_) = True
	doc (' ':'^':_) = True
	doc (' ':'*':_) = True
	doc _ = False

nextTab x = x + (tAB_LENGTH - (x-1) `mod` tAB_LENGTH)

-- 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 :: (Token -> P a) -> P a
lexBOL cont s loc y x context =
        if need_close_curly then 
                -- 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.
        	cont VRightCurly s loc y 0 (tail context)
        else if need_semi_colon then
                --trace "layout: inserting ';'\n" $
        	cont SemiColon s loc y x context
        else
        	lexToken cont s loc y x context
 where
        need_close_curly =
        	case context of
        		[] -> False
        		(i:_) -> case i of
        			    NoLayout -> False
        			    Layout n -> x < n
        need_semi_colon =
        	case context of
        		[] -> False
        		(i:_) -> case i of
        			    NoLayout -> False
        			    Layout n -> x == n

lexToken :: (Token -> P a) -> P a
lexToken cont s loc y x =
   -- trace ("lexer: y="++show y++" x="++show x++"\n") $ 
   case s of
        -- First the special symbols
        '(':'#':s -> forward 2 LeftUT s
	'(':s 	  -> forward 1 LeftParen s
	'#':')':s -> forward 2 RightUT s
        ')':s     -> forward 1 RightParen s
        ',':s     -> forward 1 Comma s
        ';':s     -> forward 1 SemiColon s
        '[':s     -> forward 1 LeftSquare s
        ']':s     -> forward 1 RightSquare s
        '`':s     -> forward 1 BackQuote s
        '{':s     -> \ctxt -> forward 1 LeftCurly s (NoLayout : ctxt)
        '}':s     -> \ctxt -> case ctxt of
                              (_:ctxt) -> forward 1 RightCurly s ctxt
						-- pop context on '}'
                              []       -> error "Internal error: empty context in lexToken"

	'-':'-':' ':'|':s -> docComment DocCommentNext cont s loc y x
	'-':'-':' ':'/':s -> docComment DocCommentNext cont s loc y x
	'-':'-':' ':'^':s -> docComment DocCommentPrev cont s loc y x
	'-':'-':' ':'*':s -> docSection cont ('*':s) loc y x

        '\'':s -> lexChar cont s loc y (x+1)
        '\"':s{-"-} -> lexString cont s loc y (x+1)

        '0':'x':c:s | isHexDigit c -> 
	   let (num, rest) = span isHexDigit (c:s)
	       [(i,_)] = readHex num
	   in
	   afterNum cont i rest loc y (x+length num)
        '0':'o':c:s | isOctDigit c -> 
	   let (num, rest) = span isOctDigit (c:s)
	       [(i,_)] = readOct num
	   in
	   afterNum cont i rest loc y (x+length num)

        c:s | isLower c || c == '_' ->
        	let 
        	    (idtail, rest) = slurpIdent s
        	    id = c:idtail
        	    l_id = 1 + length idtail
        	in
        	case lookup id reserved_ids of
        		Just keyword -> forward l_id keyword rest
        		Nothing -> forward l_id (VarId id) rest

          | isUpper c -> lexCon "" cont (c:s) loc y x
          | isSymbol c ->
        	let
        	    (symtail, rest) = span isSymbol s
        	    sym = c : symtail
        	    l_sym = 1 + length symtail
        	in
        	case lookup sym reserved_ops of
        	    Just t  -> forward l_sym t rest
        	    Nothing -> case c of
        			':' -> forward l_sym (ConSym sym) rest
        			_   -> forward l_sym (VarSym sym) rest

          | isDigit c -> lexNum cont c s loc y x

          | otherwise ->
        	parseError ("illegal character \'" ++ show c ++ "\'\n") 
        		  s loc y x

 where forward n t s = cont t s loc y (x+n)

lexToken _ _ _ _ _ = error "Internal error: empty input in lexToken"

afterNum cont i ('#':s) loc y x = cont (PrimInt i) s loc y (x+1)
afterNum cont i s loc y x = cont (IntTok i) s loc y x

lexNum cont c s loc y x = 
  let (num, after_num) = span isDigit (c:s)
  in
  case after_num of
    '.':c:s | isDigit c ->
	let (frac,after_frac) = span isDigit s
	in
	let float = num ++ '.':frac
	    (f, after_exp)
		 = case after_frac of
		    'E':s -> do_exponent s
		    'e':s -> do_exponent s
		    _     -> (float, after_frac)

	    do_exponent s =
		 case s of
		  '-':c:s | isDigit c -> 
			let (exp,rest) = span isDigit (c:s) in
			(float ++ 'e':'-':exp, rest)
		  '+':c:s | isDigit c -> 
			let (exp,rest) = span isDigit (c:s) in
			(float ++ 'e':'+':exp, rest)
		  c:s | isDigit c -> 
			let (exp,rest) = span isDigit (c:s) in
			(float ++ 'e':exp, rest)
		  _ -> (float, after_frac)

	    x' = x + length f

	in case after_exp of -- glasgow exts only
		'#':'#':s -> cont (PrimDouble f) s loc y x'
		'#':s     -> cont (PrimFloat f)  s loc y x'
		s         -> cont (FloatTok f)   s loc y x'

    _ -> afterNum cont (parseInteger 10 num) after_num loc y (x + length num)

		
-- GHC extension: allow trailing '#'s in an identifier. 
slurpIdent s = slurp' s []
 where
  slurp' [] i = (reverse i, [])
  slurp' (c:cs) i 
    | isIdent c = slurp' cs (c:i)
    | c == '#'  = slurphashes cs (c:i)
  slurp' cs i = (reverse i, cs)

slurphashes [] i = (reverse i, [])
slurphashes ('#':cs) i = slurphashes cs ('#':i)
slurphashes s i = (reverse i, s)


lexCon qual cont s loc y x =
  let
    forward n t s = cont t s loc y (x+n)

    (con, rest) = slurpIdent s
    l_con = length con

    just_a_conid 
	| null qual = forward l_con (ConId con) rest
	| otherwise = forward l_con (QConId (qual,con)) rest
  in
  case rest of
    '.':c1:s1 
     | isLower c1 ->	-- qualified varid?
	let
	    (idtail, rest1) = slurpIdent s1
	    id = c1:idtail
	    l_id = 1 + length idtail
	in
	case lookup id reserved_ids of
	   -- cannot qualify a reserved word
	   Just keyword -> just_a_conid
	   Nothing -> forward (l_con+1+l_id) (QVarId (con, id)) rest1

     | isUpper c1 ->	-- qualified conid?
        let qual' | null qual = con
		  | otherwise = qual ++ '.':con
	in
	lexCon qual' cont (c1:s1) loc y (x+l_con+1)

     | isSymbol c1 ->	-- qualified symbol?
	let
	    (symtail, rest1) = span isSymbol s1
	    sym = c1 : symtail
	    l_sym = 1 + length symtail
	in
	case lookup sym reserved_ops of
	    -- cannot qualify a reserved operator
	    Just _  -> just_a_conid
	    Nothing -> case c1 of
			':' -> forward (l_con+1+l_sym) 
				(QConSym (con, sym)) rest1
			_   -> forward (l_con+1+l_sym)
				(QVarSym (con, sym)) rest1

    _ -> just_a_conid -- not a qualified thing


lexChar :: (Token -> P a) -> P a
lexChar cont s loc y x = case s of
                    '\\':s -> (escapeChar s `thenP` \(e,s,i) _ _ _ _ ->
                               charEnd e s loc y (x+i)) s loc y x
                    c:s    -> charEnd c s loc y (x+1)
                    []     -> error "Internal error: lexChar"

  where charEnd c ('\'':'#':s) = \loc y x -> cont (PrimChar c) s loc y (x+2)
	charEnd c ('\'':s) = \loc y x -> cont (Character c) s loc y (x+1)
        charEnd c s = parseError "Improperly terminated character constant" s

lexString :: (Token -> P a) -> P a
lexString cont s loc y x = loop "" s x y
  where
     loop e s x y = case s of
            '\\':'&':s  -> loop e s (x+2) y
            '\\':c:s | isSpace c -> stringGap e s (x+2) y
        	     | otherwise -> (escapeChar (c:s) `thenP` \(e',s,i) _ _ _ _ ->
        		             loop (e':e) s (x+i) y) s loc y x
            '\"':s{-"-} -> cont (StringTok (reverse e)) s loc y (x+1)
            c:s		-> loop (c:e) s (x+1) y
            []          -> parseError "Improperly terminated string" s loc y x

     stringGap e s x y = case s of
        	'\n':s -> stringGap e s 1 (y+1)
        	'\\':s -> loop e s (x+1) y
        	c:s' | isSpace c -> stringGap e s' (x+1) y
        	     | otherwise -> 
        	       parseError "Illegal character in string gap" s loc y x
                []     -> error "Internal error: stringGap"

-- ToDo: \o, \x, \<octal> things.

escapeChar :: String -> P (Char,String,Int)
escapeChar s = case s of

  'x':c:s | isHexDigit c -> 
	let (num,rest) = span isHexDigit (c:s) in
	returnP (chr (fromIntegral (parseInteger 16 num)), rest, length num)

  'o':c:s | isOctDigit c -> 
	let (num,rest) = span isOctDigit (c:s) in
	returnP (chr (fromIntegral (parseInteger 8 num)), rest, length num)

  c:s | isDigit c -> let (num,rest) = span isDigit (c:s) in
		     returnP (chr (read num), rest, length num)

-- Production charesc from section B.2 (Note: \& is handled by caller)

  'a':s 	  -> returnP ('\a',s,2)
  'b':s 	  -> returnP ('\b',s,2)
  'f':s 	  -> returnP ('\f',s,2)
  'n':s 	  -> returnP ('\n',s,2)
  'r':s 	  -> returnP ('\r',s,2)
  't':s 	  -> returnP ('\t',s,2)
  'v':s 	  -> returnP ('\v',s,2)
  '\\':s        -> returnP ('\\',s,2)
  '"':s         -> returnP ('\"',s,2)
  '\'':s        -> returnP ('\'',s,2)

-- Production ascii from section B.2

  '^':x@(c:s)   -> cntrl x
  'N':'U':'L':s -> returnP ('\NUL',s,4)
  'S':'O':'H':s -> returnP ('\SOH',s,4)
  'S':'T':'X':s -> returnP ('\STX',s,4)
  'E':'T':'X':s -> returnP ('\ETX',s,4)
  'E':'O':'T':s -> returnP ('\EOT',s,4)
  'E':'N':'Q':s -> returnP ('\ENQ',s,4)
  'A':'C':'K':s -> returnP ('\ACK',s,4)
  'B':'E':'L':s -> returnP ('\BEL',s,4)
  'B':'S':s     -> returnP ('\BS', s,3)
  'H':'T':s  	  -> returnP ('\HT', s,3)
  'L':'F':s 	  -> returnP ('\LF', s,3)
  'V':'T':s 	  -> returnP ('\VT', s,3)
  'F':'F':s 	  -> returnP ('\FF', s,3)
  'C':'R':s 	  -> returnP ('\CR', s,3)
  'S':'O':s 	  -> returnP ('\SO', s,3)
  'S':'I':s 	  -> returnP ('\SI', s,3)
  'D':'L':'E':s -> returnP ('\DLE',s,4)
  'D':'C':'1':s -> returnP ('\DC1',s,4)
  'D':'C':'2':s -> returnP ('\DC2',s,4)
  'D':'C':'3':s -> returnP ('\DC3',s,4)
  'D':'C':'4':s -> returnP ('\DC4',s,4)
  'N':'A':'K':s -> returnP ('\NAK',s,4)
  'S':'Y':'N':s -> returnP ('\SYN',s,4)
  'E':'T':'B':s -> returnP ('\ETB',s,4)
  'C':'A':'N':s -> returnP ('\CAN',s,4)
  'E':'M':s     -> returnP ('\EM', s,3)
  'S':'U':'B':s -> returnP ('\SUB',s,4)
  'E':'S':'C':s -> returnP ('\ESC',s,4)
  'F':'S':s     -> returnP ('\FS', s,3)
  'G':'S':s     -> returnP ('\GS', s,3)
  'R':'S':s     -> returnP ('\RS', s,3)
  'U':'S':s     -> returnP ('\US', s,3)
  'S':'P':s     -> returnP ('\SP', s,3)
  'D':'E':'L':s -> returnP ('\DEL',s,4)

  _             -> parseError "Illegal escape sequence"


-- Stolen from Hugs's Prelude
parseInteger :: Integer -> String -> Integer
parseInteger radix ds =
	foldl1 (\n d -> n * radix + d) (map (toInteger . digitToInt) ds)

-- Production cntrl from section B.2

cntrl :: String -> P (Char,String,Int)
cntrl (c:s) | c >= '@' && c <= '_' = returnP (chr (ord c - ord '@'), s,2)
cntrl _                            = parseError "Illegal control character"

nestedComment cont y x bol s =
   case s of
      '-':'}':s -> cont y (x+2) bol s
      '{':'-':s -> nestedComment (nestedComment cont) y (x+2) bol s
      '\t':s    -> nestedComment cont y (nextTab x) bol s
      '\n':s    -> nestedComment cont (y+1) 1 True s
      c:s       -> nestedComment cont y (x+1) bol s
      []        -> error "Internal error: nestedComment"


docComment f cont s loc y x 
  = let (s', comment, y') = slurpExtraCommentLines s [] y in
    cont (f comment) s' loc y' x  -- continue with the newline char
    
slurpExtraCommentLines s lines y
  = case rest of
	'\n':nextline -> 
		case dropWhile nonNewlineSpace nextline of 
		  -- stop slurping if we see a string of more than two '-';
		  -- strings of dashes are useful as separators but we don't
		  -- want them in the doc.
		  '-':'-':c:s | c /= '-'
			 -> slurpExtraCommentLines (c:s)
				((line++"\n"):lines) (y+1)
		  _ -> (rest, finished, y)
	other -> (rest, finished, y)
  where
	(line, rest) = break (== '\n') s
	finished = concat (reverse (line:lines))

nonNewlineSpace c = isSpace c && c /= '\n'

docSection cont s loc y x
  = let (stars, rest') = break (/= '*') s
        (line,  rest) = break (== '\n') rest'
    in
    cont (DocSection (length stars) line) rest loc y x
\end{code}