Handling of non-layout sections in HsParser
HsParser fails on any of these 6 examples:
data Data = A {
x :: Int
}
f1 x = let {
s = x
} in s
f2 x = do {
x
}
f3 x = case x of {
_ - 12
}
f4 x = s where {
s = 12
}
f5 y = A {
x = 45
}
The problem seems to be the production (copied from HsParser.ly)
layout_off :: { () } : {% pushContext NoLayout }
This production is supposed to make the parser enter a NoLayout
context every time the lexer reaches an open brace '{'. It is used in
other productions such as
decllist :: { [HsDecl] }
: '{' layout_off decls '}' { $3 }
| layout_on decls close{ $2 }
For some reason the use of layout_off only takes effect _after_ the
lexer has produced the next token. When the lexer reaches the second x
in
f2 x = do {
x
}
the NoLayout hasn't been pushed yet. Since x is indented to the same
column as f2, the lexer therefore inserts a ';'. The '{' followed by a ';'
causes the parser to fail. In code with a more normal indentation
f2 x = do {
x
}
the parser works fine, because the lexer in this case doesn't insert
an extra ';' or '}'.
One way of fixing this is to remove all uses of layout_off, and
instead delegate the pushing of NoLayouts to the lexer. I have
attached a patch of HsParser.ly and HsLexer.lhs to show what I had in
mind.
Anders
233c233
'{' - special LeftCurly
---
'{' - \ctxt - special LeftCurly (NoLayout : ctxt)
130c130
: '{' layout_off bodyaux '}' { $3 }
---
: '{' bodyaux '}' { $2 }
286c286
: '{' layout_off decls '}' { $3 }
---
: '{' decls '}' { $2 }
370,371c370,371
| srcloc con '{' layout_off fielddecls '}'
{ HsRecDecl $1 $2 (reverse $5) }
---
| srcloc con '{' fielddecls '}'
{ HsRecDecl $1 $2 (reverse $4) }
417c417
: 'where' '{' layout_off cbody '}' { $4 }
---
: 'where' '{' cbody '}' { $3 }
438c438
: 'where' '{' layout_off valdefs '}'{ $4 }
---
: 'where' '{' valdefs '}' { $3 }
506c506
: aexp '{' layout_off fbinds '}' {% mkRecConstrOrUpdate $1 (reverse $4) }
---
: aexp '{' fbinds '}' {% mkRecConstrOrUpdate $1 (reverse $3) }
571c571
: '{' layout_off alts optsemi '}' { reverse $3 }
---
: '{' alts optsemi '}' { reverse $2 }
601c601
: '{' layout_off stmts '}'{ $3 }
---
: '{' stmts '}' { $2 }
738d737
layout_off :: { () }: {% pushContext NoLayout }
RE: Handling of non-layout sections in HsParser
HsParser fails on any of these 6 examples:
[...]
The problem seems to be the production (copied from HsParser.ly)
layout_off :: { () }: {% pushContext NoLayout }
This production is supposed to make the parser enter a NoLayout
context every time the lexer reaches an open brace '{'. It is used in
other productions such as
decllist :: { [HsDecl] }
: '{' layout_off decls '}' { $3 }
| layout_on decls close{ $2 }
For some reason the use of layout_off only takes effect _after_ the
lexer has produced the next token.
Yes, Happy seems to be grabbing a lookahead token, even though it
doesn't need to. Anyway, your fix is the right one because it avoids
this non-deterministic behaviour in Happy, and it brings HsParser into
line with the way that GHC's parser works.
I've committed your patches, thanks!
Cheers,
Simon
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RE: Flags in GHCi
I noticed a difference in behavior between running: ghci -package utils And: ghci ... Prelude :set -package utils On our system, the first one works (it finds all the right dynamic libraries and stuff), but the second one doesn't (it cannot find libreadline.so, and other dynamic libraries). Thanks, this bug will be fixed in 5.02.1. Cheers, Simon ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
ghc-5.02: panic! NoCgInfo!
Hello, when I try to compile the program below with ghc -fglasgow-exts it says ghc-5.02: panic! (the `impossible' happened, GHC version 5.02): NoCgInfo! I couldn't find a smaller example because little modifications make the problem go away, e.g. - removing the type signature for `k' - replacing `y ([] ++ [[]] ++ [])' by `y ([] ++ [[]])' - changing the definition of `g' or `h', e.g. h ys = map (k (y [[0]])) ys Regards, Armin module Test where import List (transpose) data X a = X a class Y a b | a - b where y :: a - X b instance Y [[a]] a where y ((x:_):_) = X x g :: Num a = [X a] - [X a] g xs = h xs where h ys = ys ++ map (k (y [[0]])) xs k :: X a - X a - X a k _ _ = y ([] ++ [[]] ++ []) ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
¯uªº¡IµL±ø¥ó°e±z¤â¾÷»Pªù¸¹
§ÚÌÃØ°e±z¤â¾÷+ªù¸¹¡I¡I¡I¡I¡I ¨S¿ù¡I¡I§ÚÌÃØ°e±z¤â¾÷+ªù¸¹¡I¡I¡I¡I¡I ³oµ´¹ï¬O¯u¹êªº¡I ½Ð¤£n¦AÃhºÃ¤F¡I¡I §ÚÌ©M±z¤@¼Ë¬Oµ½¨}¡B¥¿ª½ªº¦Ñ¦Ê©m¡I¡I «ô°U¡I¡I «ô°U¡I¡I½Ð¤£n¦AÃhºÃ§ÚÌ¡I¡I¡I¡I ¤]½Ð¤£n¦A¥´¹q¸Ü¸ß°Ý©M«H¹q°T¤F¡A ³oÓÃØ°e¤è®×»P©M«H¹q°T¨S¦³Ãö«Y¡I §Ú̬O±¶°\¥ø·~ºÞ²zÅU°Ý¦³¤½¥q¡A ¬O§ÚÌÃØ°e±z¤â¾÷+ªù¸¹¡A¤£¬O©M«H¹q°T¡C ©ÒÃØ°e¤§§K¶O¤è®×¦p¤U¡G ªù¸¹¡G ©M«Hªù¸¹ ³q¸Ü¶Op¶O¤è®×¡G ©M«Hºëºâ188 ÃØ°e¤â¾÷¡G MOTOROLA T2288¡]^¤å¾÷¡^ ºëºâ188¤ë¯²¶O¡G 188¤¸ §K¶O³q¸Ü¡G ©è188¤¸¤ë¯²¶O ¤@¯ë®É¬q¡G 0.16¤¸/¬í¡A¶g¤@¦Ü¶g¤é¥þ¤é ´î»ù®É¬q¡G ¦P¤@¯ë®É¬q¦¬¶O ¥»ºô¤¬¥´¡G 0.08¤¸/¬í¡]¥b»ù¡^ ¡]ºëºâ188p¶O¤è¦¡¹ï¥ô¦ó©M«H¨Ï¥ÎªÌ¬Ò¬Û¦P¡^ ¥t¦³¦Xºâ¥I¶O¤è®×¦p¤U¡G ªù¸¹¡G ©M«Hªù¸¹ ³q¸Ü¶Op¶O¤è®×¡G ©M«H«¢©Ô900 ¤â¾÷¡G Nokia 3310¡]¤¤¤å¾÷¡^ ¥Ó½Ð¦¹´Ú¤â¾÷»Ý¥I¶O888¤¸¡A ¤ñ¦b¤@¯ë³q°T¦æ¥Ó½Ð¡A«K©y1000¤¸¥H¤W «¢©Ô900¤ë¯²¶O¡G 900¤¸ ¨C¤ë§K¶O³q¸Ü¤ÀÄÁ¡G 200¤ÀÄÁ ¤@¯ë®É¬q 0.11¤¸/¬í ´î»ù®É¬q 0.11¤¸/¬í ºô¤º¤¬¼·¨C³q«e5¤ÀÄÁ¤º§K¶O¡F ¶W¹L³¡¥÷¡G1¤¸/¤À¡A ¥¼º¡1¤ÀÄÁ¥H1¤ÀÄÁp ¡]«¢©Ô900p¶O¤è¦¡¹ï¥ô¦ó©M«H¨Ï¥ÎªÌ¬Ò¬Û¦P¡^ ½Ðª`·N¡G«¢°Õ900¨C¤ë§K¶O³q¸Ü¤ÀÄÁ¼Æ¡A·í¤ë¥¼¥Î§¹ªº¡A ¤£±o»¼©µ¨ì¤UÓ¤ë¨Ï¥Î¡C «¢°Õ900¤§¨C¤ë§K¶O³q¸Ü¤§200¤ÀÄÁ¤£§tºô¤º¤¬¼·¡C «¢°Õ900©M«Hºô¤º¤¬¼·¦³§K¶O³W©w¡A ºëºâ188ºô¤º¤¬¼·¦³¥b»ù³W©w¡A ³Ì¾A¦X±`±`¬Û¤¬Ápµ¸ªºªB¤Í̤@°_¥Ó½Ð¡C ºëºâ188»P«¢°Õ900¤§ªù¸¹¨Ï¥Î´Á³W©w¬°¦Ü¤Ö¨â¦~¡A »P¦b¤@¯ë³q°T¦æ¥Ó½Ð¬Û¦P¡C ¤é«áªº³q¸Ü¶O¡A±z¥i¦b©M«Hªù¥«¡B7-11¡B¶×´Ú¡B¹º¼·..µ¥µ¥Ãº¯Ç¡A ·íµM¤]¥i¥Ñ©M«H¹q°T±Ä»È¦æ±b¸¹¦Û°Ê¦©´Ú¤è¦¡¡C ¡]¨C¤ë³q¸Ü¶O¥I¶O¤è¦¡¹ï¥ô¦ó©M«H¨Ï¥ÎªÌ¬Ò¬Û¦P¡^ ¥Ó½Ðªù¸¹©Ò»ÝÃÒ¥ó 1.±z»Ý·Ç³Æ¨¥÷ÃÒ¼v¥»¡]¥¿¤Ï±¡^ 2.»È¦æ¦sºP«Ê±¼v¥»¡]»P¨¥÷ÃÒ¬Û¦P¦W¦r¡^ 3.«K³¹¤@Áû¡]»P¨¥÷ÃÒ¼v¥»¦W¦r¬Û¦P¡A¤£»Ýn¦LŲÃÒ©ú¹Ï³¹¡^ ¡]ªù¸¹¥Ó½Ð¤è¦¡¹ï¥ô¦ó©M«H¨Ï¥ÎªÌ¬Ò¬Û¦P¡^ ¥Ó½Ð¬ù¤@¬P´Á«á¡A«K¥i¨Ï¥Î¡C ¦P¤@Ó¦W¦r¡A³Ì¦h¥Ó½Ð3Óªù¸¹+3Ó¤â¾÷ ¬O¯uªº½Ð¬Û«H¡I µL±ø¥ó°e±z¤â¾÷»P©M«H¹q°Tªù¸¹¡I ¦p¿ï¾Ü§K¶O¤è®×¡A±z¤£¥²¥X¥ô¦ó¥b¤ò¿ú¡A§Y¥i¾Ö¦³¤â¾÷¡Ïªù¸¹¡I ¦p¿ï¾Ü¦Xºâ¥I¶O¤è®×¡A±z¥un¥I888¤¸¡A§Y¥i¾Ö¦³¤â¾÷¡Ïªù¸¹¡I ¦³·NÄ@¥Ó½ÐªÌ¡A½Ð¨Ó¥»¤½¥q¿ì²z¡I Åwªï¨Ó¹q¸ß°Ý¡G 02-27039827 0925851019 ±¶°\¥ø·~ºÞ²zÅU°Ý¦³¤½¥q·q¤W ²Î¤@½s¸¹¡G97225510 ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
/tmp/ghc13435.lpp:388: Non-exhaustive patterns in function zip_ty_env
Hi, When I compile the following module, module ZipTyEnvBug where type A i = i type B = A I get ghc-5.02: panic! (the `impossible' happened, GHC version 5.02): /tmp/ghc13435.lpp:388: Non-exhaustive patterns in function zip_ty_env Changing the second declaration to type B i = A i helps, but the Haskell 98 report (section 4.2.2) explicitly allows the lhs of a type sysonym declaration to be of higher kind... Regards, Thomas Hallgren ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Robustness of instance Read Char
Folks,
my code has unwillingly been forced to read a large string generated
by show. This turned out to be a robustness test because the effect is
a stack overflow (with Hugs as well as with GHC) and, of course, this
error happened in a CGI script.
If you want to try the effect yourself, just take a file foo of,
say, 150k and type this into you hungry Hugs prompt:
readFile foo = \s - putStr (read (show foo))
Digging down into the prelude code (taken from Hugs's prelude file),
you find this:
instance Read Char where
readsPrec p = readParen False
(\r - [(c,t) | ('\'':s,t) - lex r,
(c,\') - readLitChar s ])
readList = readParen False (\r - [(l,t) | ('':s, t) - lex r,
(l,_) - readl s ])
where readl ('':s) = [(,s)]
readl ('\\':'':s) = readl s
readl s= [(c:cs,u) | (c ,t) - readLitChar s,
(cs,u) - readl t ]
which means that the parser reading this string has the ability to
fail and to backtrack *at every single character*. While this might be
useful in the general case, it certainly causes our little one-line
program to die.
Unfortunately, in my real program, the String is embedded in a data
type which is deriving Read, so that writing the specific instance of
read is a major pain. Two things would help me in this situation:
1. some kind-hearted maintainer of a particularly well-behaved Haskell
implementation might put in a more efficient definition in the
instance Read Char (or convince me that backtracking inside of
reading a String is a useful gadget). The following code will do:
readListChar :: String - [(String, String)]
readListChar =
return . readListChar' . dropWhile isSpace
readListChar' ('\':rest) =
readListChar'' rest
readListChar'' ('\':rest) =
(,rest)
readListChar'' rest =
let (c, s') = head (readLitChar rest)
(s, s'') = readListChar'' s'
in (c:s, s'')
{- clearly, taking the head should be guarded and a proper error
message generated -}
2. provide a way of locally replacing the offending instance of Read
with something else. [urgh, a language extension]
Any suggestions or comments?
-Peter
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Re: Haskell Communities Survey - Second Call for Contributions
Hi all, I'm sending this to the whole list because maybe there are others who are doing the same thing as me, and so it would be useful to share some effort. What about a standard AST format? What about static analysis and type checking/inference? A few of us at Melbourne have been slowly creating a front end to Mark Jones' Typing Haskell in Haskell. It is getting close to being useable. It is intended as a stand-alone type inference/checking tool that can give detailed information about static aspects of the program. It will understand modules. Given Mark's approval I would like to make it available to the Haskell community. I think seperating this element of the language from the compilers is a useful thing to do, especially for program transformations that need types. It uses the Hsparser library for parsing. As for a standard AST and interface, that would be lovely but I think it is as much a language issue as a library issue. I think there was some people working on making the front end of GHC more independent from the rest of the compiler. I'm not sure if this is still happening. Regards, Bernie. ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Standard Prelude - Floating Class
Jerzy Karczmarczuk wrote: Did Joe Fasel include this consciously? If yes, my respect - already almost infinite, is even bigger now). I'm pretty sure he did, but he can speak for himself. I know he discussed these things with his numerical collegues when designing the prelude. Look at this definition (from Complex, by Joe) for instance instance (RealFloat a) = Fractional (Complex a) where (x:+y) / (x':+y') = (x*x''+y*y'') / d :+ (y*x''-x*y'') / d where x'' = scaleFloat k x' y'' = scaleFloat k y' k = - max (exponent x') (exponent y') d = x'*x'' + y'*y'' The scaleFloat calls are there for numeric reasons. -- Lennart ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Standard Prelude - Floating Class
I wrote I'm afraid that I have very little faith in the numerical analysis expertise of the typical Haskell implementor, so I think it is dangerous to give them an incorrect default implementation. I am reminded of the notorious ASCII C (very)-pseudo-random number generator . . . Dylan wrote I don't think it's worth worrying about much. I wrote This is a good argument for leaving things as they are. Jerzy Karczmarczuk wrote Absolutely NO. Unless you don't care at all about the potential scientific users of the language. Leaving the details which are of utmost importance for professional applications is killing the language. Most readers of this forum are very far away from numerics, and this is normal. But languages live through their libraries. At least 4 times a year somebody on this list complains about lack of such a support even if the actual libraries are already quite impressive. The potential scientific users of the language are not going to be well served if the language includes *incorrect* implementations of mathematical functions. This is my point. So, I would encourage to organize one day a group - not necessarily a task force like the GUI people - of people who would test all the numerics, and at least give to the freshmen some implementation prototypes, e.g. Padés for small arguments of sinh, etc Yes, in the ideal world, we would form a group of numerically-knowledgable Haskell people who would test things out properly. Well, perhaps. I would like to be on this group. I at least know what a Pad'e approximation is, and perhaps I could even remember how you find them. I have implemented sinh properly in ML based on the netlib specification. Still, I am not a numerical analyst, and I am not sure we are going to be able to find it easy to assemble a group of numerical analysts willing to give time to define the transcendental functions properly. I also doubt if this is going to be possible. At the moment for example, Haskell cannot even require IEEE arithmetic, because virtually no platform supports it completely. (Intel has too much precision which needs to be artificially clobbered if we want IEEE, Alpha doesn't do underflows properly unless you are very careful with inserting traps to fix things up.) So getting a standard which specifies exactly what Haskell transcendental functions should do (be accurate within 0.8ULP for example, though when you think about it that is horrendously complicated to guarantee in some instances . . .) is going to be tricky, to say the least. And what is this: typical Haskell implementor? Do you know many of them? Do you think really that some fellow totally inconscious in the domain of STANDARD numeric maths, somebody who never heard about IEEE etc. will NOW engage in implementing Haskell? What is the rationale behind your little faith, Man of Little Faith? I think numerical analysis is a prime example of A little learning is a dangerous thing. I think I would like a Haskell implementor to be either totally ignorant of numerical analysis, and simply call out to C routines written by an expert, such as the excellent ones available at netlib. Or else a Haskell implementor should be a skilled numerical analyst. Unfortunately expecting writers of functional compilers to be an s.n.a. seems to me rather like expecting them to be brain surgeons; it just isn't so. On the other hand, they have enough mathematical learning to know about sinh(x)=(exp(x)-exp(-x))/2, so they erroneously introduce it into their code, having forgotten whatever they learnt in bright college days about never subtracting two nearly-equal floating-point numbers. Standard ML/NJ and Microsoft Excel (when I tested it a couple of years ago) both get sinh wrong, so I think my pessimism is well-grounded. Incidentally, another fruitful example of ALLIADT is random number generators. I have yet to see a language standard which defined a random number generator which wasn't completely pathetic. ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Haskell 98 - Standard Prelude - Floating Class
Tue, 16 Oct 2001 15:29:36 +1000, Fergus Henderson [EMAIL PROTECTED] pisze: Not giving a default definition is *not* the same as giving a default definition that calls error. It's significantly safer. The difference is that the former makes it much easier for compilers to issue warnings when you forget to define a class method in an instance declaration. There are no warnings when default definitions are expressed in terms of themselves such that when no explicit definition is present, they will diverge. In practice this is analogous to not having a definition at all. But the compiler sees this as if they had a good definition. If we are serious about ensuring that definitions are not omitted, we should handle this case too. It can be done with a pragma which tells the compiler and a programmer who wants to make instances what are possible sets of methods to be provided by instances (in terms of conjunctions and alternatives). This is often already specified in comments. An optimizing compiler could detect most of such incomplete instances itself, with the help of strictness analysis. -- __( Marcin Kowalczyk * [EMAIL PROTECTED] http://qrczak.ids.net.pl/ \__/ ^^ SYGNATURA ZASTÊPCZA QRCZAK ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
ANNOUNCE: popenhs-0.00 released
I am happy to announce the first release of popenhs, version 0.00. popenhs is a very small Haskell library, based on runProcess in hslibs' posix library. It provides lazy output from subprocesses through two functions popen2 and popen3. The source and rpm files are available from: http://www.01.246.ne.jp/~juhp/haskell/popenhs/ I welcome comments and feedback. Jens ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
ExitFailure 127
hi. I'm trying to run an system command (wget) within a CGI script and get the following error: Exitfailure 127 How can I get more information out of an ExitFailure x error? Can I use ioeGetErrorString? But this function doesn't work on ExitCode, which system returns. TIA sebastian ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
