Problem when compiling with -prof -fasm
Hello, when compiling anything with -prof -fasm, I get the following response: ghc-6.0: panic! (the `impossible' happened, GHC version 6.0): AbsCStixGen.gencode CC_DECLARE(CGI_CAFs_cc,CAF,CGI,CC_IS_CAF,); Please report it as a compiler bug to [EMAIL PROTECTED], or http://sourceforge.net/projects/ghc/. (without -fasm I get Prologue junk?: .globl __stginit_CGI .type __stginit_CGI,@function __stginit_CGI: pushl %ebp movl%esp, %ebp instead, which is probably caused by non-supported version of gas or gcc?) Zdenek Dvorak ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: int to float problem
Hello, [snip] Try intToFloat :: Int - Float intToFloat n = fromInteger (toInteger n) [snip] Use the Prelude function realToFrac. it sometimes happens to me that I must spend some time browsing prelude to devise somethink like this; it might be useful to have a library for this, that would define class Coerce a b where coerce :: a-b of course this cannot work without multiparametric type classes. Zdenek _ Help STOP SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: FiniteMap performance WITHOUT any copying?
Hello, Now, Haskell has a garbage collector, so Haskell must know how many pointers there are to all objects in the heap (or?). Then, if a finite map for example only has one single pointer to it, then it ought to be all right to modify the finite map (or whatever datastructure we are considering), I mean really modify the map without making any copies, just like in imperative languages. Perhaps there might be pointers to nodes inside the tree and I guess that could complicate the matter somewhat. But for Haskell arrays it ought to be possible to really modify the array if it is used by only one pointer ? Are such optimizations possible, and if they are, are they already implemented in for example GHC ? Or am I wrong somewhere ? You are more or less right; except that -- the Haskell implementations I have seen do not keep number of pointers to objects (gc in principle works by traversing the graph made by pointers, marking reachable nodes and finally removing the unreachable ones; just keeping the number of references is not sufficient due to cyclic structures) -- due to lazy evaluation, the situation where there would be just one pointer to array is rare Zdenek _ Add photos to your messages with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: default class methods in sub-classes
Hello, Apparently I can't do this (in ghc or hugs -- haven't tried others): class Space a where distance :: a - a - Int subtract :: a - a - a class (Space a) = NormSpace a where norm :: a - Int distance a b = norm (subtract a b) That is, I can't make (or redefine) a default for the superclass method 'distance' in a subclass. I agree that the Haskell'98 definition doesn't claim that this should be allowed, but it seems like something that would be useful. Are there reasons not to allow this (or that I shouldn't want to do this at all)? Apologies if this is well-covered. I couldn't find any mention of it. the problem is, that to make something instance of NormSpace, you must first have it as instance of Space, i.e. with distance already defined. Then for this to work, the default definition in NormSpace would have to override what user defined, which looks strange. Your problem can be solved in ghc by this (but unfortunately only with -fallow-overlapping-instances -fallow-undecidable-instances (or some simmilar flags)): class HavingSubtract a where -- not sure why generic space should have subtract, subtract :: a - a - a -- but why not class (HavingSubtract a) = Space a where distance :: a - a - Int class (HavingSubtract a) = NormSpace a where norm :: a - Int instance (NormSpace a) = Space a where distance a b = norm (subtract a b) (and there is several more examples in that I would find something like this very useful, but AFAIK there is no clean and elegant way how to do it -- you may do something simmilar using newtypes, but that is totally clumsy). Zdenek _ The new MSN 8: smart spam protection and 2 months FREE* http://join.msn.com/?page=features/junkmail ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: avoiding cost of (++)
Hello, I have a function which behaves like map, except instead of applying the given function to, say, the element at position 5, it applies it to the entire list *without* the element at position 5. An implementation looks like: mapWithout :: ([a] - b) - [a] - [b] mapWithout f = mapWith' [] where mapWith' pre [] = [] mapWith' pre (x:xs) = f (pre ++ xs) : mapWith' (x:pre) xs Unfortunately, this is very slow, due to the overhead of (++). Any way I could speed this up would be great. Note that order doesn't matter to 'f', but I do need that the order in which the elements of the list are processed be the same as in map. two remarks: 1) as long as f works on single list, there is no way how to make things faster (IMHO) 2) this solution is up to constant factor optimal due to laziness (at most one step of ++ will be evaluated for each element f needs) Zdenek Dvorak _ Protect your PC - get McAfee.com VirusScan Online http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963 ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Question About Random Module
Hello, Hello! I just Wanna Know, What should I do, to build a List of random Numbers, without IO type, just Float or Int the answer for this is either you can't, read something about IO and monads (good starting places are http://haskell.org/wiki/wiki?UsingIo and http://haskell.org/wiki/wiki?UsingMonads, and reading other FAQs there is a good idea, too) or you should not, but if you really have to, browse this mailing list archives, where you'll find the answer 1000x, depending on what you are asking for. Zdenek _ MSN 8 helps eliminate e-mail viruses. Get 3 months FREE*. http://join.msn.com/?page=features/virusxAPID=42PS=47575PI=7324DI=7474SU= http://www.hotmail.msn.com/cgi-bin/getmsgHL=1216hotmailtaglines_virusprotection_3mf ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Running out of memory in a simple monad
Hello, I hope I understand what's going on; if not please someone correct me. I have problems with monads and memory. I have a monad through which I thread output. If I do the concatenation of the output-strings in one way Hugs runs out of memory, but if I do it in another way everything works. I can't see why the first way doesn't work but the second is OK. I woudl appreciate if someone could tell me what I am doing wrong. Here is the non-working monad: -} The problem is not directly connected to monads; what is the problem: [] ++ x = x (h:t) ++ x = h : (t++x), i.e. time complexity of ++ is proportional to the length of first list. first way: putCharM c = M $ \o - ((), o ++ [c]) -- Is this stupid in some way? this takes list (looong) of everything produced before this putCharM and concatenates c as last member; this takes time linear in the length of the list, summing over all putCharMs it is quadratic (and of course, due to laziness a lot of memory is consumed; seq does not help, as it only evaluates first cell of the list so that it sees it is not empty; deepSeq would solve this, but the time consumption would still stay long). the second way: M f = k = M $ let (x, o) = f M f2 = k x (x', o') = f2 in (x', o ++ o') this is done reverse way (because = is bracketed to the right); we concatenate output of f (short) with output of f2 (the rest of computation, i.e. looong); but the time is proportional to the length of first list, so it is constant in our case; summing it over all putCharMs, we get linear time and we are happy :-) If you want to do it the first way, define putCharM c = M $ \o - ((), c : o) and then reverse the list in runM. Zdenek Dvorak _ Add photos to your messages with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: need help optimizing a function
Hello, p.s., I sense your next question is going to be something like why can't the compiler detect that the array can be updated in place instead of copied and the answer, from what i can tell, is simply that it doesn't try. And one might argue that it should not try [snip] and the other answer is that the result would not be worth the effort usually. The idea seems nice, but the laziness is where I see the problem; see the following code: do_something::Array Int Int-(Array Int Int, Result) do_something a = (a'',res) where a' = a // [(summon_index, summon_int)] w = a' ! 4 res = do_some_work w a'' = a' // [(summon_other_index, summon_other_int)] Seems like nice candidate for update-in-place? But the problem is, that in general you cannot say when w will be evaluated -- so you simply cannot destroy a' before then. This is also reason why DiffArray (from hslibs) does not have to be very useful, unless you have a good control on when things are evaluated -- it may (and it also happened to me) have quadratic behavior in cases like this. To solve this, '!' would have to produce a new array too; but then you must pass it everywhere and effectively you are doing the work monads would do for you. So in general you must choose -- either your programs will be nice and functional, but you will have to use structures with (some kind of) logarithmic slowdown (FiniteMap, Trie), or some of their parts will be embedded in monads. Zdenek Dvorak _ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: how to debug?
Hello, How does one debug in haskell? I have a function that I could swear should behave differently than it does, and after tracking down bugs for many hours, I'm wondering if there's any way to step through the evaluation of a haskell function? The other way I would be debugging in an imperative language would be to sprinkle printfs around. Is there any way to do something like that cleanly in haskell? The only thing I can think of would be to modify every function to accept an additional parameter, which seems like it's more likely to introduce bugs than remove them... For what it's worth I'm using ghc, and the only debugging options it seems to have are for debugging the compiler itself. I would be happy to install and use hugs for debugging if it has some nicer debugging mode. I have already isolated my bug within one function, but that function has somewhat funky recursion, and uses an array (which I'm none too familiar with in haskell), and there aren't any smaller parts that I can see to test. :( aside from (useful) general advices already given, just few tips that I found useful when I needed to debug: -- to print debug dumps, you may use 'trace' function from IOExts (but beware, it may affect behavior of your program if used incorrectly) -- other way (safer, but slower to learn and use) is to use Hood library -- if your program fails with some really informative error message of type '*** Exception: Maybe.fromJust: Nothing', compiling it with profiling (-prof -auto-all) and running with +RTS -xc will give you a stack dump (pretty useful, well hidden feature :-) Zdenek Dvorak _ Chat with friends online, try MSN Messenger: http://messenger.msn.com ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Pretty printing (was: Standard Library for text formatting?)
Hello, After doing some searching, it seems that pretty printing is a prominant Haskell way of doing text output. I still am interested in finding a library of standard text formatting (String formatting) functions, but it seems like it might be worth my while investigating pretty printing. Pretty printing is not very suited for printf like formatting, I have looked for something simmilar some time ago, but unsuccesfully. Pretty printing libraries are not very useful for breaking paragraphs into lines, distributing spaces evenly, etc. (at least I was not able to persuade them to work like that). I have written following module that implements stupid first-fit algorithm for these purposes; the interface is simmilar to the pretty printing libraries. Zdenek Dvorak module ReportPrinter ( LowDoc,HighDoc, (),(+),($$),($), int, lowText, text, empty, colon, comma, space, semi, period, brackets, parens, vcat, sep, punctuate, high, nest, par, render ) where data LowDoc=Text String | Join LowDoc LowDoc | Append LowDoc LowDoc | Empty deriving (Show) data HighDoc=HLowDoc LowDoc | Paragraph Int HighDoc | Nest Int HighDoc | Above HighDoc HighDoc | Beside HighDoc HighDoc deriving (Show) ()::LowDoc-LowDoc-LowDoc x Empty = x Empty x = x x y = Join x y (+)::LowDoc-LowDoc-LowDoc x + Empty = x Empty + x = x x + y = Append x y ($)::HighDoc-HighDoc-HighDoc x $ HLowDoc Empty=x HLowDoc Empty $ x=x x $ y=Beside x y ($$)::HighDoc-HighDoc-HighDoc x $$ HLowDoc Empty=x HLowDoc Empty $$ x=x x $$ y=Above x y lowText::String-LowDoc lowText=Text text::String-LowDoc text str=sep $ map lowText $ words str int::Int-LowDoc int=text . show empty::LowDoc empty=Empty colon::LowDoc colon=lowText : comma::LowDoc comma=lowText , space::LowDoc space=lowText semi::LowDoc semi=lowText ; period::LowDoc period=lowText . brackets::LowDoc-LowDoc brackets doc=lowText [ doc lowText ] parens::LowDoc-LowDoc parens doc=lowText ( doc lowText ) sep::[LowDoc]-LowDoc sep=foldl (+) empty high::LowDoc-HighDoc high=HLowDoc vcat::[HighDoc]-HighDoc vcat=foldl ($$) (high empty) punctuate::LowDoc-[LowDoc]-[LowDoc] punctuate _ [] = [] punctuate _ [x] = [x] punctuate pun (h:t) = (h pun) : punctuate pun t nest::Int-HighDoc-HighDoc nest=Nest par::Int-HighDoc-HighDoc par=Paragraph render::Int-HighDoc-String render width doc=highRender width 0 0 doc highRender::Int-Int-Int-HighDoc-String-String highRender width indFirst indRest doc rest= case doc of HLowDoc lowDoc - lowRender width indFirst indRest lowDoc rest Paragraph ind pDoc - highRender width indFirst (indRest+ind) pDoc rest Nest ind pDoc - highRender width (indFirst+ind) (indRest+ind) pDoc rest Above doc1 doc2- highRender width indFirst indRest doc1 $ highRender width indRest indRest doc2 rest Beside doc1 doc2 - error Rendering two HighDocs beside not supported. lowRender::Int-Int-Int-LowDoc-String-String lowRender width indFirst indRest doc rest= stringRender width indFirst indRest strs rest where (strs,_) = stringify False doc [] stringify False (Text txt) rest = ((txt,length txt):rest,False) stringify True (Text txt) [] = ([(txt,length txt)],False) stringify True (Text txt) ((txt',len'):rest) = ((txt++txt',length txt+len'):rest,False) stringify join Empty rest = (rest,join) stringify join (Append doc1 doc2) rest = let (rest',join')=stringify join doc2 rest in stringify join' doc1 rest' stringify join (Join doc1 doc2) rest = let (rest',_)=stringify join doc2 rest in stringify True doc1 rest' stringRender::Int-Int-Int-[(String,Int)]-String-String stringRender width indFirst indRest [] rest=rest stringRender width indFirst indRest strs rest= let (lne,rst)=cutLine (width-indFirst) strs rest'=stringRender width indRest indRest rst rest in lineRender (rst==[]) width indFirst lne rest' cutLine tot ((txt,len):t)=(txt:lne',rst) where (lne',rst)=cutLine' (tot-len) t cutLine' ml []=([],[]) cutLine' ml r@((tx,ln):t') | mlln = let (lne'',rst')=cutLine' (ml-ln-1) t' in (tx:lne'',rst') | otherwise = ([],r) lineRender::Bool-Int-Int-[String]-String-String lineRender last width ind lne rest=indent ind rslt where totlen = sum $ map length lne words= length lne reqlen = totlen + words - 1 havelen = width - ind distsp = if havelen reqlen not last then havelen - reqlen else 0 count= words `div` 2 rslt = distribSpaces count distsp words lne rest indent n = (take n (cycle ) ++) distribSpaces::Int-Int-Int-[String]-String-String distribSpaces _ _ _ [h] rest = h ++ '\n' : rest distribSpaces count minus plus (h:t) rest = h ++ ' ' : spaced where (spaced,count') = recount count rest' = distribSpaces (count'-minus) minus plus t rest recount cnt | cnt 0 = let
RE: comparison of execution speed of array types
Hello, DiffArray seems to be broken :). Either that or I'm using it incorrectly. I've attached the relevant code, but when I don't reverse the array everything works fine; when I reverse it the program doesn't (seem to) halt. I've tried to use DiffArray recently and it is terribly slow. I was forced to write my own version (it is a bit faster, but still nothing great). My suspicion about the result of your measuring is that it does the updates in reversing the array one by one, thus leading to quadratic behavior. Zdenek Dvorak _ Chat with friends online, try MSN Messenger: http://messenger.msn.com ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Defining instances of superclasses
Hello. I've got the following problem: I have class Structure, that says that its members have some internal parts that can be read from/written to Strings: data StrItem a=forall b c.(Show b,Parse c)=StrItem String (a-b) (a-c-a) class Structure a where strName::a-String strEmpty::a strItems::[StrItem a] Now I would like to use it to create instances of Show and Parse (and perhaps others (for input/output from various formats, ...)). The approaches I have tried: 1) instance Structure a = Show a where showsPrec _ w = showsStruct (strName w) (map showsPair strItems) where showsPair (StrItem fName fGet _)=(fName,shows $ fGet w) This is nice, but it only works in ghc with allowed overlapping and undecidable instances. It may not seem too important, when I use existential types anyway, but existential types are supported by at least one more implementation (hugs) and they seem to me to be a well defined extension that has good chances to become part of standard Haskell later; handling of overlapping and undecidable instances in ghc seems quite too much ad-hoc and experimental for me. 2) newtype Str a=Str a instance Structure a = Show (Str a) where showsPrec _ (Str w) = showsStruct (strName w) (map showsPair strItems) where showsPair (StrItem fName fGet _)=(fName,shows $ fGet w) This seems to be a standard way how to do it. The problem is, that I don't get Show instance for a, but for isomorphic type Str a; this is a bit annoying when I want to use it; also I may no longer use deriving Show on types containing such structure. Is there some better way how to do this? Zdenek Dvorak _ Send and receive Hotmail on your mobile device: http://mobile.msn.com ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Haskell digest, Vol 1 #656 - 3 msgs
Hello. Can I write dependencies like this: class C x y z | x - (y, z) class D x y z | (x, y) - z in hugs? in ghc? The ghc doc refers to Mark Jones: Type Classes with Functional Dependencies, http://www.cse.ogi.edu/~mpj/pubs/fundeps.html where this seems to be allowed (section 4, page 9) Especially, I would need class D above. class C can be rewritten to class C x y z | x - y, x - z concerning class D, I used (in GHC) class D x y z | x y - z and it seemed to do what I wanted. I guess class C x y z | x - y z would work too. Zdenek Dvorak _ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Haskell puzzles!
Hello. - All the answers are at the end of this mail. - 1) Are e1 and e2 equal? f (x:xs) y = x g (x:xs)= \y - x e1 = seq (f []) 1 e2 = seq (g []) 1 Should not these be f (x:xs) y = y g (x:xs)= \y - y ? Otherwise, both e1 and e2 are obviously undefined. Zdenek Dvorak _ Chat with friends online, try MSN Messenger: http://messenger.msn.com ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
