Re: [Haskell-cafe] Language simplicity
On Tue, Jan 12, 2010 at 11:26 PM, Daniel Fischer
daniel.is.fisc...@web.dewrote:
Okay, 'as' is easy. But can you find a situation where 'qualified' or
'hiding' would be natural choices for an identifier? I'd love to see those
in some code :)
module LordsOfMidnight.Character(Character) where
data Character = C { name :: String,
location :: (Int,Int),
facing :: Direction,
hour :: Int,
energy :: Int,
fear :: Int,
riders :: Int,
soldiers :: Int,
hiding :: Bool
}
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Re: [Haskell-cafe] Language simplicity
On 12 Jan 2010, at 21:25, Andrew Coppin wrote: OK people, it's random statistics time! Haskell '98 apparently features 25 reserved words. (Not counting forall and mdo and so on, which AFAIK are not in Haskell '98.) So how does that compare to other languages? C: 32 C++: 62 Borland Turbo Pascal: ~50 [without the OOP extensions added later] Eiffel: 59 VB: The source I checked listed in excess of 120 reserved words, but I'm dubious as to how reserved they really are. (Is CInt really reserved? I doubt it!) It also depends wildly on which of the bazillion VB dialects you mean. Java: 50 JavaScript: 36 Smalltalk: 0 There are six singleton pseudo-variables that act as reserved words: true,false, nil, self, super and thisContext. Lisp: AFAIK, there are no truly reserved words in Lisp, only predefined functions. (??) All Lisps have special forms which are evaluated uniquely and differently from function application and are therefore reserved words by another name. For example, Clojure has def, if, do, let, var, quote, fn, loop, recur, throw, try, monitor-enter, monitor-exit, dot, new and set!. Python: 31 Ruby: 38 Tcl: Same analysis as for Lisp I believe. COBOL: Over 400 (!) As you can see, this conclusively proves... something. Generally speaking, the most widely used languages seem to be near the upper end of the range. I don't think it really tells you that much. Possibly that a little superficial complexity through syntactic sugar can make your language a lot more human-friendly, but that it's possible to go too far and end up like C++. Martin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On 12 Jan 2010, at 22:22, Andrew Coppin wrote: Niklas Broberg wrote: Haskell '98 apparently features 25 reserved words. (Not counting forall and mdo and so on, which AFAIK are not in Haskell '98.) 21 actually. case, class, data, default, deriving, do, else, if, import, in, infix, infixl, infixr, instance, let, module, newtype, of, then, type, where. There's also three special words that can still be used as identifiers, so aren't reserved: as, qualified, hiding. OK. Well the list I saw was for Haskell plus extensions, and I visually filtered out the inapplicable stuff. Apparently I missed something. Also, the number varies depending on whether you consider reversed words or keywords, Aye, there's a subtle distinction between keywords and reserved words, but I think for the purposes of this discussion, they're the same thing. Martin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
As you can see, this conclusively proves... something. What about brainfuck? 8 different signs are used. - http://de.wikipedia.org/wiki/Brainfuck#cite_note-0 The first link points to a page saying there is an interpreter 98 bytes in size.. What does this prove? :-) Marc Weber ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: FASTER primes
Daniel Fischer wrote: Heinrich Apfelmus wrote: It is exactly because these troubles that I'm advocating the original VIP data structure that buries the dorks (that name is awesome :D) deep inside the structure. :) In fact, your transformation that fixes the space leaks pretty much emulates the behavior of the old data People a = VIP a (People a) | Dorks [a] structure. This becomes apparent if we put the last two arguments of spMerge back into a pair: mergeSP (P a b) ~(P c d) = let P bc m = spMerge b (P c d) in P (a ++ bc) m where spMerge b (P [] d) = P [] (merge b d) spMerge xs@(x:xt) cd@(P (y:yt) d) = case compare x y of LT - celebrate x (spMerge xt cd ) EQ - celebrate x (spMerge xt (P yt d)) GT - celebrate y (spMerge xs (P yt d)) In particular, forcing dorks (mergeSP ...) also forces the complete VIP list. I wonder whether it's really the liveness of pair in mergeSP (a,b) pair = let sm = spMerge b (fst pair) in (a ++ fst sm, merge (snd sm) (snd pair)) that is responsible for the space leak, for chances are that Sparud's technique applies and pair is properly disposed of. Rather, it could be that we need the stronger property that forcing the second component will evaluate the first to NF. In any case, it appears to me that the lazy pattern match in mergeSP is actually unnecessary! This is because mergeSP returns a pair constructor immediately, so infinite nesting works even when the second argument is demanded. [...] No, loop. For the reason you stated below. In tfold f (a:b:c:xs) = (a `f` (b `f` c)) `f` smartfold f xs , it must compute smartfold f xs too early to match it against P c d. The compiler can't see that smartfold mergeSP always returns a P [well, it might return _|_, mightn't it?]. Oops, silly me! Mea culpa, of course mergeSP a (mergeSP b (mergeSP c ..))) or any infinite nesting is not going to work with a strict pattern. _ _ Regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] QuickCheck: test passes in GHCi, fails when compiled
I provided a Java solution to a problem of returning the first digit
of an integer on StackOverflow and someone wondered if there were any
floating point point problems with the solution, so I though I'd
implement the algorithm in Haskell and run QuickCheck on it.
Everything works fine on GHCi, but if I compile the code and run the
test, it fails with -1000, 1000, -100. Any ideas why?
In any case it seems that the commenter was right and there are some
subtle problems with my solution. I'd just like to know more
details...
import Data.Char
import Test.QuickCheck
-- my solution
getFirstDigit :: Int - Int
getFirstDigit 0 = 0
getFirstDigit x = let x' = abs x
digits = (floor $ logBase 10 $ fromIntegral x')
in x' `div` (floor $ 10 ** (fromIntegral digits))
-- two reference implementation that agree with each other
getFirstDigitRef1 :: Int - Int
getFirstDigitRef1 x = digitToInt $ head $ show $ abs x
getFirstDigitRef2 :: Int - Int
getFirstDigitRef2 x | x 0 = getFirstDigitRef2 (-x)
| x 10 = x
| otherwise = getFirstDigitRef2 $ x `div` 10
myTest x = getFirstDigit x == getFirstDigitRef1 x
--myTest x = getFirstDigitRef2 x == getFirstDigitRef1 x
myCheck n = check (defaultConfig { configMaxTest = n }) myTest
main = myCheck 10
--
! Lauri
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Re: [Haskell-cafe] Language simplicity
sylvain sylvain.na...@googlemail.com writes: Let me order your list: Smalltalk: 0 Lisp: 0 Tcl: 0 If you count reserved tokens, I guess Lisp reserves parentheses and whitespace? Haskell: 21 * Python: 31 C: 32 * JavaScript: 36 Ruby: 38 --- Borland Turbo Pascal: ~50 Java: 53 Eiffel: 59 C++: 62 Interestingly enough, interpreted languages tend to need less keywords, which support my observation above. I can't help but notice that the top three are untyped (all right, dynamically typed) languages. Static typing seems to require at least a few reserved words (does it make sense to redefine 'data' or 'type' in Haskell?) But if you really wanted to compare apples to apples you would, for instance, add GHC pragmas and magic things like `par` to the mix. I wonder if the picture would change much? Looking for a minimal subset that everything else can be implemented in terms of? Still, having 'par' as a user redefinable token lets you replace it with your own implementation (par = seq, for instance :-). So I think there's a benefit, even if it is normally implemented using magic. -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP?
On Sun, Nov 1, 2009 at 2:57 AM, Gregory Collins g...@gregorycollins.netwrote: Doing OO-style programming in Haskell is difficult and unnatural, it's true (although technically speaking it is possible). That said, nobody's yet to present a convincing argument to me why Java gets a free pass for lacking closures and typeclasses. I might be wrong, but doesn't Java's concepts of inner classes and interfaces together with adapter classes can be used to replace closures and typeclasses in a way? An inner class allows you to implicitly capture the parent object (environment), just like a closure does in a sense. Interfaces group together methods, like type classes do. Although I'm actually a C# fanboy for doing industrial programming, I think the Java designers did an excellent job, finding a good balance in language features, ease of use and readability, and although C# does offer closures and many more FP constructs, I really miss the above Java constructs. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP?
On 13 Jan 2010, at 09:51, Peter Verswyvelen wrote: On Sun, Nov 1, 2009 at 2:57 AM, Gregory Collins g...@gregorycollins.net wrote: Doing OO-style programming in Haskell is difficult and unnatural, it's true (although technically speaking it is possible). That said, nobody's yet to present a convincing argument to me why Java gets a free pass for lacking closures and typeclasses. I might be wrong, but doesn't Java's concepts of inner classes and interfaces together with adapter classes can be used to replace closures and typeclasses in a way? Inner classes are not a semantic replacement for closures, even if you discount horrific syntax. Inner classes do not close over their lexical environment. Martin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Type Inference for Overloading without Restrictions
A while ago, someone provided me a link to the paper Type Inference for Overloading without Restrictions http://www.dcc.ufmg.br/~camarao/ct-flops99.ps.gz Although I don't understand everything in this paper, I wander what people's opinions are about this regarding a future Haskell language revision or extension? Would a feature like this be preferable over typeclasses? Would it be practical to implement? Are people working on this? Thanks, Peter Verswyvelen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP?
The problem with interfaces as a replacement for type classes is that they only provide dispatch based on the specific type of the first argument (i.e. the receiver). Type classes allow you to dispatch based on return type, and on the instantiations of generic parameters. Neither of these things is reasonably possible with interfaces. For example you can't directly implement the Read type class with interfaces. Neither can you implement a function of type [a] - ... where the dispatch is based on the instantiation of a - even if you can add an interface to the [] generic type, you might not have a concrete object of type a to dispatch from if the empty list is passed as an argument. From: haskell-cafe-boun...@haskell.org [mailto:haskell-cafe-boun...@haskell.org] On Behalf Of Peter Verswyvelen Sent: 13 January 2010 09:52 To: Gregory Collins Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP? On Sun, Nov 1, 2009 at 2:57 AM, Gregory Collins g...@gregorycollins.net wrote: Doing OO-style programming in Haskell is difficult and unnatural, it's true (although technically speaking it is possible). That said, nobody's yet to present a convincing argument to me why Java gets a free pass for lacking closures and typeclasses. I might be wrong, but doesn't Java's concepts of inner classes and interfaces together with adapter classes can be used to replace closures and typeclasses in a way? An inner class allows you to implicitly capture the parent object (environment), just like a closure does in a sense. Interfaces group together methods, like type classes do. Although I'm actually a C# fanboy for doing industrial programming, I think the Java designers did an excellent job, finding a good balance in language features, ease of use and readability, and although C# does offer closures and many more FP constructs, I really miss the above Java constructs. === Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html === ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: QuickCheck: test passes in GHCi, fails when compiled
2010/1/13 Lauri Pesonen lauri.peso...@iki.fi: I provided a Java solution to a problem of returning the first digit of an integer on StackOverflow and someone wondered if there were any floating point point problems with the solution, so I though I'd implement the algorithm in Haskell and run QuickCheck on it. Everything works fine on GHCi, but if I compile the code and run the test, it fails with -1000, 1000, -100. Any ideas why? In any case it seems that the commenter was right and there are some subtle problems with my solution. I'd just like to know more details... Ok, I've figured out why the compiled version fails the check: main = putStrLn $ show $ logBase 10 1000 when compiled returns 2.9996 on my system (WinXp 32-bit) which then gets truncated to 2. So it seems that there's a precision difference between the compiled and the interpreted code. 'logBase 10 999' on the other hand produces exactly the same value in both cases. I expect this to be a known issue with floats. Sorry for the noise. -- ! Lauri ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP?
On Jan 13, 2010, at 11:00 AM, Sittampalam, Ganesh wrote: Type classes allow you to dispatch based on return type, and on the instantiations of generic parameters. Neither of these things is reasonably possible with interfaces. There is recent work that generalises the capabilities of interfaces in Java: http://www.informatik.uni-freiburg.de/~wehr/publications/WehrLammelThiemann2007.html http://www.informatik.uni-freiburg.de/~wehr/publications/WehrThiemann2009.html http://www.informatik.uni-freiburg.de/~wehr/publications/Wehr2009.html Seeing type-class features in Java disguise highlights the differences between the two concepts that you mention. Sebastian -- Underestimating the novelty of the future is a time-honored tradition. (D.G.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On Jan 13, 2010, at 03:49 , Martin Coxall wrote: COBOL: Over 400 (!) If we're going to go that far, FORTRAN and PL/1 have none. FORTRAN is somewhat infamous for this: DO 10 I = 1, 400 is a loop start, DO 10 I = 1. 400 (note typo, . for ,) parses as the assignment DO10I = 1.400. (This is often cited as the cause of the failure of Mariner 1, but that's an urban legend. See http://catless.ncl.ac.uk/Risks/9.54.html#subj1.1 for discussion, including the possible origin of this UL.) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP?
Yes that is true, but often in Haskell I had to use type annotations when the dispatch is based on the return type, so it also has some tradeoffs. Don't get me wrong, I see the advantages of Haskell's type classes and closures, and I love these. But in Java - if you stay close to OO, and don't try to do FP - you can accomplish a lot, albeit with a lot of boilerplate. IMO, it's not because you have less lines of code in Haskell, that the code becomes more readable per se. I'm not a Java expert, but I have no troubles at all reading Java code, even though that code is typically twice as long as similar C# code, and maybe ten times as long as Haskell or ML code (at least if the side effects are kept local enough, which is good practice in OO anyway). But after many years of playing with Haskell, I still fail to read and understand a lot of Haskell code (maybe because it is written by people with a much higher IQ than mine I guess) On Wed, Jan 13, 2010 at 11:00 AM, Sittampalam, Ganesh ganesh.sittampa...@credit-suisse.com wrote: The problem with interfaces as a replacement for type classes is that they only provide dispatch based on the specific type of the first argument (i.e. the receiver). Type classes allow you to dispatch based on return type, and on the instantiations of generic parameters. Neither of these things is reasonably possible with interfaces. For example you can't directly implement the Read type class with interfaces. Neither can you implement a function of type [a] - ... where the dispatch is based on the instantiation of a - even if you can add an interface to the [] generic type, you might not have a concrete object of type a to dispatch from if the empty list is passed as an argument. From: haskell-cafe-boun...@haskell.org [mailto:haskell-cafe-boun...@haskell.org] On Behalf Of Peter Verswyvelen Sent: 13 January 2010 09:52 To: Gregory Collins Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP? On Sun, Nov 1, 2009 at 2:57 AM, Gregory Collins g...@gregorycollins.net wrote: Doing OO-style programming in Haskell is difficult and unnatural, it's true (although technically speaking it is possible). That said, nobody's yet to present a convincing argument to me why Java gets a free pass for lacking closures and typeclasses. I might be wrong, but doesn't Java's concepts of inner classes and interfaces together with adapter classes can be used to replace closures and typeclasses in a way? An inner class allows you to implicitly capture the parent object (environment), just like a closure does in a sense. Interfaces group together methods, like type classes do. Although I'm actually a C# fanboy for doing industrial programming, I think the Java designers did an excellent job, finding a good balance in language features, ease of use and readability, and although C# does offer closures and many more FP constructs, I really miss the above Java constructs. == Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html == ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: QuickCheck: test passes in GHCi, fails when compiled
On Jan 13, 2010, at 05:07 , Lauri Pesonen wrote: I expect this to be a known issue with floats. Sorry for the noise. Yep. There's a faction that wants Float and Double to not be in the Eq typeclass, because floating point calculations can never reliably be compared for equality. (There are some infinite precision float packages out there, but transcendentals will still get you in trouble even if repeating decimals don't.) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] FFI, C/C++ and undefined references
But when I try to compile it (after having successfully compiled the C code with g++), I get: $ ghc --make Main.hs You are not telling ghc to link against the C/C++ code, e.g. ghc --make Main.hs srilm.o Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
Fraser Wilson blancoli...@gmail.com writes:
module LordsOfMidnight.Character(Character) where
data Character = C { name :: String,
location :: (Int,Int),
facing :: Direction,
hour :: Int,
energy :: Int,
fear :: Int,
riders :: Int,
soldiers :: Int,
hiding :: Bool
}
Daniel Fisher thinks again...
(With apologies for the rather obscure reference.)
-k
--
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Re: [Haskell-cafe] Language simplicity
Brandon S. Allbery KF8NH allb...@ece.cmu.edu writes: If we're going to go that far, FORTRAN and PL/1 have none. FORTRAN is somewhat infamous for this: There's also the option (perhaps this was PL/1?) of writing constructs like: IF THEN THEN IF ELSE THEN etc. Having few reserved words isn't necessarily a benefit. :-) -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On Jan 13, 2010, at 05:45 , Ketil Malde wrote: Brandon S. Allbery KF8NH allb...@ece.cmu.edu writes: If we're going to go that far, FORTRAN and PL/1 have none. FORTRAN is somewhat infamous for this: There's also the option (perhaps this was PL/1?) of writing constructs like: IF THEN THEN IF ELSE THEN etc. Having few reserved words isn't necessarily a benefit. :-) That'd be PL/I, and a prime example of why languages use keywords these days (as if FORTRAN weren't enough). :) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] wildcards for type variables?
On Wed, Jan 13, 2010 at 12:29 AM, Evan Laforge qdun...@gmail.com wrote: Occasionally I have a function with an unused argument, whose type I don't want to restrict. Thus: f :: _unused - A - B f _ a = b I probably misunderstood the problem, why not f:: a - A - B David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] wildcards for type variables?
On Jan 13, 2010, at 05:54 , David Virebayre wrote: On Wed, Jan 13, 2010 at 12:29 AM, Evan Laforge qdun...@gmail.com wrote: Occasionally I have a function with an unused argument, whose type I don't want to restrict. Thus: f :: _unused - A - B f _ a = b I probably misunderstood the problem, why not f:: a - A - B He's looking for the self-documentation aspect of this argument is completely irrelevant. Neither rolling a random unused type variable nor foralling it (my first idea) really accomplishes that. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] FFI, C/C++ and undefined references
Hello DNM,
Wednesday, January 13, 2010, 8:57:45 AM, you wrote:
Note: I'm relatively new to Haskell, and my knowledge of C and C++ is
basically pretty
minimal -- I can read, modify and compile C/C++ programs (usually).
1. you use too much unsafePerformIO. since you need newCString, i
suggest you to declare C functions as returning IO a so your code
will be
unsafePerformIO$ do
withCString str $ \c_str - do
c_function c_str ...
2. if your function returns Ptr a - then hold in haskell types this Ptr a.
no need to convert it back and forth to ForeignPtr
3. why c_dlm is FunPtr in your definition? it should be
foreign import ccall srilm.h deleteLM
c_dlm :: Ptr Ngram - IO ()
4. i don't looked in your code but if C functions defines
*modifiable* datastructure - you should use it at Haskell side via
imperatiove functions, i.e. those with return type IO a. using
unsafePerformIO in this case will lead to Haskell compiler will
consider this datatype as permanent and reorder operations on the will
so,
data NGModel = NGModel {ng :: !(Ptr Ngram)}
foreign import ccall srilm.h bldLM
c_blm :: CInt - CString - IO (Ptr Ngram)
foreign import ccall srilm.h deleteLM
c_dlm :: Ptr Ngram - IO ()
foreign import ccall srilm.h getSeqProb
c_ngramProb :: Ptr Ngram - CString - CUInt - CUInt - IO CFloat
scoreSequence :: NGModel - Int - [String] - IO Float
scoreSequence ngram order seq = do
withCString (unwords seq) $ \stringSeq - do
sc - c_ngramProb (ng ngram) stringSeq (fromIntegral order)
(fromIntegral $ length seq)
return (realToFrac sc)
and so on
--
Best regards,
Bulatmailto:bulat.zigans...@gmail.com
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Re: [Haskell-cafe] Re: FASTER primes
Am Mittwoch 13 Januar 2010 10:43:42 schrieb Heinrich Apfelmus:
I wonder whether it's really the liveness of pair in
mergeSP (a,b) pair
= let sm = spMerge b (fst pair)
in (a ++ fst sm, merge (snd sm) (snd pair))
that is responsible for the space leak, for chances are that Sparud's
technique applies and pair is properly disposed of. Rather, it could
be that we need the stronger property that forcing the second component
will evaluate the first to NF.
I think that is responsible. At least that's how I understand the core:
mergeSP (a,b) ~(c,d) = (a ++ bc, merge b' d)
where
(bc, b') = spMerge b c
spMerge ...
--
OldMerge.$wmergeSP :: [GHC.Types.Int]
- [GHC.Types.Int]
- ([GHC.Types.Int], [GHC.Types.Int])
- (# [GHC.Types.Int], [GHC.Types.Int] #)
GblId
[Arity 3
Str: DmdType LLL]
OldMerge.$wmergeSP =
\ (ww_sny :: [GHC.Types.Int])
(ww1_snz :: [GHC.Types.Int])
(w_snB :: ([GHC.Types.Int], [GHC.Types.Int])) -
let {
ds_so7 [ALWAYS Just D(SS)] :: ([GHC.Types.Int], [GHC.Types.Int])
LclId
[Str: DmdType]
ds_so7 =
case w_snB of _ { (c_adj, _) -
case OldMerge.$wspMerge ww1_snz c_adj
of _ { (# ww3_snH, ww4_snI #) -
(ww3_snH, ww4_snI)
}
} } in
(# GHC.Base.++
@ GHC.Types.Int
ww_sny
(case ds_so7 of _ { (bc_ajQ, _) - bc_ajQ }),
case ds_so7 of _ { (_, b'_ajS) -
case w_snB of _ { (_, d_adk) - OldMerge.merge b'_ajS d_adk }
-- Here, in the second component of the result,
-- we reference the entire pair to get the dorks
} #)
OldMerge.mergeSP :: ([GHC.Types.Int], [GHC.Types.Int])
- ([GHC.Types.Int], [GHC.Types.Int])
- ([GHC.Types.Int], [GHC.Types.Int])
GblId
[Arity 2
Worker OldMerge.$wmergeSP
Str: DmdType U(LL)Lm]
OldMerge.mergeSP =
__inline_me (\ (w_snw :: ([GHC.Types.Int], [GHC.Types.Int]))
(w1_snB :: ([GHC.Types.Int], [GHC.Types.Int])) -
case w_snw of _ { (ww_sny, ww1_snz) -
case OldMerge.$wmergeSP ww_sny ww1_snz w1_snB
of _ { (# ww3_snN, ww4_snO #) -
(ww3_snN, ww4_snO)
}
})
--
vs.
mergeSP (a,b) ~(c,d) = (a ++ bc, m)
where
(bc,m) = spMerge b c d
spMerge ...
--
NewMerge.$wmergeSP :: [GHC.Types.Int]
- [GHC.Types.Int]
- ([GHC.Types.Int], [GHC.Types.Int])
- (# [GHC.Types.Int], [GHC.Types.Int] #)
GblId
[Arity 3
Str: DmdType LLL]
NewMerge.$wmergeSP =
\ (ww_snB :: [GHC.Types.Int])
(ww1_snC :: [GHC.Types.Int])
(w_snE :: ([GHC.Types.Int], [GHC.Types.Int])) -
let {
ds_soa [ALWAYS Just D(SS)] :: ([GHC.Types.Int], [GHC.Types.Int])
LclId
[Str: DmdType]
ds_soa =
case w_snE of _ { (c_adj, d_adk) -
-- There's no reference to the pair after this
case NewMerge.$wspMerge ww1_snC c_adj d_adk
of _ { (# ww3_snK, ww4_snL #) -
(ww3_snK, ww4_snL)
}
} } in
(# GHC.Base.++
@ GHC.Types.Int
ww_snB
(case ds_soa of _ { (bc_ajT, _) - bc_ajT }),
case ds_soa of _ { (_, b'_ajV) - b'_ajV } #)
NewMerge.mergeSP :: ([GHC.Types.Int], [GHC.Types.Int])
- ([GHC.Types.Int], [GHC.Types.Int])
- ([GHC.Types.Int], [GHC.Types.Int])
GblId
[Arity 2
Worker NewMerge.$wmergeSP
Str: DmdType U(LL)Lm]
NewMerge.mergeSP =
__inline_me (\ (w_snz :: ([GHC.Types.Int], [GHC.Types.Int]))
(w1_snE :: ([GHC.Types.Int], [GHC.Types.Int])) -
case w_snz of _ { (ww_snB, ww1_snC) -
case NewMerge.$wmergeSP ww_snB ww1_snC w1_snE
of _ { (# ww3_snQ, ww4_snR #) -
(ww3_snQ, ww4_snR)
}
})
--
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Re: [Haskell-cafe] wildcards for type variables?
On Wed, Jan 13, 2010 at 4:59 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: On Jan 13, 2010, at 05:54 , David Virebayre wrote: On Wed, Jan 13, 2010 at 12:29 AM, Evan Laforge qdun...@gmail.com wrote: Occasionally I have a function with an unused argument, whose type I don't want to restrict. Thus: f :: _unused - A - B f _ a = b I probably misunderstood the problem, why not f:: a - A - B He's looking for the self-documentation aspect of this argument is completely irrelevant. Neither rolling a random unused type variable nor foralling it (my first idea) really accomplishes that. Isn't that what we have here? a function of type (a - A - B) cannot use the first argument in any meaningful way. But once you start throwing in higher ranked types you might have to think a bit to come to that conclusion. Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP?
Peter Verswyvelen bugf...@gmail.com writes: On Sun, Nov 1, 2009 at 2:57 AM, Gregory Collins g...@gregorycollins.net wrote: Doing OO-style programming in Haskell is difficult and unnatural, it's true (although technically speaking it is possible). That said, nobody's yet to present a convincing argument to me why Java gets a free pass for lacking closures and typeclasses. I might be wrong, but doesn't Java's concepts of inner classes and interfaces together with adapter classes can be used to replace closures and typeclasses in a way? Maybe, in the same sense that a lawnmower engine strapped to a skateboard is a replacement for a car: it takes you ten times as long to get to your destination and you're cold and wet when you get there. G -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] wildcards for type variables?
On Jan 13, 2010, at 2:16 PM, Antoine Latter wrote: He's looking for the self-documentation aspect of this argument is completely irrelevant. Neither rolling a random unused type variable nor foralling it (my first idea) really accomplishes that. Isn't that what we have here? a function of type (a - A - B) cannot use the first argument in any meaningful way. I think, he wants to document that the type variable 'a' is not used in the *type*. Just like you can document that the second argument of 'const' is unused by using a wildcard. You can write const x _ = x instead of const x y = x and it would be nice to write 'const's type as a - _ - a rather than a - b - a Sebastian -- Underestimating the novelty of the future is a time-honored tradition. (D.G.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] what is *hack*?
Hi, References to a Hack. module came in the responses to my posts on HTML-GUIs. What is Hack then? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what is *hack*?
http://hackage.haskell.org/package/hack 2010/1/13 Günther Schmidt gue.schm...@web.de Hi, References to a Hack. module came in the responses to my posts on HTML-GUIs. What is Hack then? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what is *hack*?
Hi John, thanks, I should have mentioned that I had found it on hackage, I just don't understand what it *is* or what it's supposed to be for. Günther Am 13.01.10 14:46, schrieb John Van Enk: http://hackage.haskell.org/package/hack 2010/1/13 Günther Schmidt gue.schm...@web.de mailto:gue.schm...@web.de Hi, References to a Hack. module came in the responses to my posts on HTML-GUIs. What is Hack then? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org mailto:Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what is *hack*?
This may help more: http://wiki.github.com/nfjinjing/hack The Hack project is based off of a project known as Rack for ruby. I'm fairly sure the documentation you can find on Rack will help you understand what Hack does. 2010/1/13 Günther Schmidt gue.schm...@web.de Hi John, thanks, I should have mentioned that I had found it on hackage, I just don't understand what it *is* or what it's supposed to be for. Günther Am 13.01.10 14:46, schrieb John Van Enk: http://hackage.haskell.org/package/hack 2010/1/13 Günther Schmidt gue.schm...@web.de Hi, References to a Hack. module came in the responses to my posts on HTML-GUIs. What is Hack then? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what is *hack*?
2010/1/13 John Van Enk vane...@gmail.com: This may help more: http://wiki.github.com/nfjinjing/hack The Hack project is based off of a project known as Rack for ruby. I'm fairly sure the documentation you can find on Rack will help you understand what Hack does. Not knowing what Rack is myself I found this, and assume that's the Ruby project you refer to: http://rack.rubyforge.org/ /M -- Magnus Therning(OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Xhtml?
Hi, apologies upfront. As time presses I decided to post questions immediately as soon as I run into dead-ends. I just don't want to give the impression that I'm not willing to do my homework. I'm trying to find documentation on Xhtml, the site on hackage refers to http://www.cse.ogi.edu/~andy/html/intro.htm for an introduction to the library, the link is dead. I managed to locate Andy Gill's current homepage (http://www.cse.ogi.edu/~andy/html/intro.htm) but there is no mention of his html combinatory library. Does anyone else know where an introduction to this library can be retrieved from? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Xhtml?
Am 13.01.10 15:31, schrieb Günther Schmidt: Hi, apologies upfront. As time presses I decided to post questions immediately as soon as I run into dead-ends. I just don't want to give the impression that I'm not willing to do my homework. I'm trying to find documentation on Xhtml, the site on hackage refers to http://www.cse.ogi.edu/~andy/html/intro.htm for an introduction to the library, the link is dead. I managed to locate Andy Gill's current homepage (http://www.cse.ogi.edu/~andy/html/intro.htm) but there is no mention of his html combinatory library. sry, I meant this site here: http://www.ittc.ku.edu/~andygill/index.php Does anyone else know where an introduction to this library can be retrieved from? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Web application interface
Hi, I recently read (again) the wiki page on a web application interface[1] for Haskell. It seems like this basically works out to Hack[2], but using an enumerator instead of lazy bytestring in the response type. Is anyone working on implementing this? If not, I would like to create the package, though I wouldn't mind some community input on some design decisions: * Hack has been fairly well-tested in the past year and I think it provides the features that people want. Therefore, I would want to model the Environment variable for WAI from Hack. I *could* just import Hack in WAI and use the exact same Environment data type. Thoughts? * If using a different data type for Environment, should I replace the String parts with ByteStrings? On the one hand, ByteStrings are the correct data type since the HTTP protocol does not specify a character encoding; on the other hand, Strings are easier to deal with. * It's simple to write a function to convert between a lazy bytestring and an enumerator, meaning it would be very easy to write conversion functions between Hack and WAI applications. This would make it simpler for people to use either backend. If someone else is already working on WAI, please let me know, I don't want to have duplicate implementations. The idea here is to consolidate, not split the community. I have a few Hack handlers (simpleserver, cgi, fastcgi) that I would happily convert to WAI handlers as well. Michael [1] http://www.haskell.org/haskellwiki/WebApplicationInterface [2] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hack ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what is *hack*?
Günther, Hack is a layer between a web application and a web server. It allows you to write a web application once and have it communicate with the server in different ways simply by swapping the handler. For example, I have applications that I test on my local system using hack-handler-simpleserver and then deploy onto an Apache server using either hack-handler-cgi or hack-handler-fastcgi. Michael 2010/1/13 Günther Schmidt gue.schm...@web.de Hi John, thanks, I should have mentioned that I had found it on hackage, I just don't understand what it *is* or what it's supposed to be for. Günther Am 13.01.10 14:46, schrieb John Van Enk: http://hackage.haskell.org/package/hack 2010/1/13 Günther Schmidt gue.schm...@web.de Hi, References to a Hack. module came in the responses to my posts on HTML-GUIs. What is Hack then? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Xhtml?
2010/1/13 Günther Schmidt gue.schm...@web.de: Am 13.01.10 15:31, schrieb Günther Schmidt: Hi, apologies upfront. As time presses I decided to post questions immediately as soon as I run into dead-ends. I just don't want to give the impression that I'm not willing to do my homework. I'm trying to find documentation on Xhtml, the site on hackage refers to http://www.cse.ogi.edu/~andy/html/intro.htm for an introduction to the library, the link is dead. I managed to locate Andy Gill's current homepage (http://www.cse.ogi.edu/~andy/html/intro.htm) but there is no mention of his html combinatory library. sry, I meant this site here: http://www.ittc.ku.edu/~andygill/index.php Does anyone else know where an introduction to this library can be retrieved from? Günther Hi, By Xhtml, do you mean the xhtml package on hackage [1] ? Maybe to get you started: $ ghci Prelude :m + Text.XHtml.Strict Prelude Text.XHtml.Strict putStrLn . prettyHtmlFragment $ p (primHtml hello) ! [theclass foo] p class=foo hello /p The idea is to create values of type Html, e.g. primHtml, combine them to make bigger document, e.g. with p or (+++), possibly with some attributes, e.g. with (!), then eventually render the final Html value, e.g. with prettyHtmlFragment. Try it in ghci! HTH, cheers Thu [1] http://hackage.haskell.org/package/xhtml ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ssh ports for monk and nun?
Trying to get ssh working via putty from behind my company firewall. My recommendation is to get access to an outside machine where you run an OpenVPN server on port 80 or 443. This will solve it once and for all. But first, please complain loudly and repeatedly about the firewall being closed to port 22. Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP?
On Wed, Jan 13, 2010 at 4:56 AM, Martin Coxall pseudo.m...@me.com wrote: On 13 Jan 2010, at 09:51, Peter Verswyvelen wrote: On Sun, Nov 1, 2009 at 2:57 AM, Gregory Collins g...@gregorycollins.net wrote: Doing OO-style programming in Haskell is difficult and unnatural, it's true (although technically speaking it is possible). That said, nobody's yet to present a convincing argument to me why Java gets a free pass for lacking closures and typeclasses. I might be wrong, but doesn't Java's concepts of inner classes and interfaces together with adapter classes can be used to replace closures and typeclasses in a way? Inner classes are not a semantic replacement for closures, even if you discount horrific syntax. Inner classes do not close over their lexical environment. Martin Anonymous classes in Java close over their lexical environment (can refer to variables in that lexical environment, with values bound at the time of instance construction) with the caveat that only local variables/parameters marked as 'final' may be referred to. Aside from the horrible syntax, this is the key distinction between them, and, say, Ruby closures. Referring to mutable variables from inside a closure has its drawbacks, making the horrible syntax the biggest stumbling block to using them IMHO (other than runtime overhead, which I believe is also an issue). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] wildcards for type variables?
Isn't that what we have here? a function of type (a - A - B) cannot use the first argument in any meaningful way. I think, he wants to document that the type variable 'a' is not used in the *type*. Yeah, that's the idea, sorry if I wasn't clear. In the case of const, I might write const :: a - _b - a To document that 'b' intentionally appears only once, but this is only my convention and I've never seen anyone else use it. In the case of 'const' it's pretty obvious and unnecessary, but in a longer signature it might help a bit, especially if you are using phantom types and some functions intentionally ignore type arguments. I haven't used them before, but in the presence of scoped type variables, wouldn't have a reader have to go look for internal definitions to reassure himself that the type is in fact ignored entirely? It's not a big issue, but it seemed like a nice symmetry with pattern matching syntax. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Name overloading
Hi,
these days I'm thinking about name scoping in Haskell and a question
built up silently but steadily in my mind.
Many times I see code like this:
data Foo = { fooBar :: Int, fooSay :: String, fooClose :: String }
which reminds me of Ye Olde Times of C where you prepend the
structure name (or an abbreviation) to the structure's fields so as to
avoid clashes with other (possibly included) structures (here Haskell
qualified imports don't help as they just let you cut down the size of
the prefix which is still present though and is module-scoped anyway).
One of the most appreciated (at least by me) features of OOP languages
like C++, Java, Python and co. is the possibility to name instance
methods the same in different classes and have the compiler resolve to
the correct implementation (at least indirectly through a virtual
table when inheritance is in place) simply looking at the type of the
variable which - is applied to. The most fulgid example of this is
the open method, which is likely to be present in lots of classes.
Now, in Haskell we have type inference, which is The Good Thing as
it allows to validate your program at compile time. Hence, the idea
coming up to my mind is that type inference actually forbids a
type-directed resolution of names as in C++ or Java.
Is this correct?
Think about this piece of code:
data DB = { open :: DBHandle }
data FS = { open :: File }
foo x = open x
or, worse:
foo x = open (open x)
if the result of the first open application should typecheck with
the second. Notice that, in my understanding, adding a signature
doesn't help as the type checker must guarantee that foo code
complies with its signature, which is actually impossible if open is
left undetermined in its type.
Thank you for any comment.
Cristiano
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Re: [Haskell-cafe] Name overloading
Hello Cristiano,
Wednesday, January 13, 2010, 9:43:06 PM, you wrote:
coming up to my mind is that type inference actually forbids a
type-directed resolution of names as in C++ or Java.
you are right. we either have ad-hoc polymorphism like in C++ where
type of id selected based on type of arguments, like in
int open(char *s)
int open(int i)
or two-way type inference where each id has just one type. otherwise,
having both overloaded ids and two-way inference, we will got
polynomial raise of complexity of type inferencing. ie. imagine some
f = a . b . c . d
where a,b,c,d have multiple possible types
there is backdorr to this mechanism - you can define foo inside of
class. moreover, you can use this to overload struct fields:
class HasFoo a b where
foo :: a - b
data X = {fooX :: Int}
data Y = {fooY :: Char}
instance HasFoo X Int where foo=fooX
instance HasFoo Y Char where foo=fooY
although error messages may be not ideal ;)
--
Best regards,
Bulatmailto:bulat.zigans...@gmail.com
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Re: [Haskell-cafe] Name overloading
The usual suggestion I see for this sort of thing is to create a typeclass for the operations you care about[1][2]. For example: --- class HasOpen a where open :: a - Handle data DB data FS openDB :: DB - Handle openFS :: FS - Handle instance DB HasOpen where open = openDB instance FS HasOpen where open = openFS --- Of course, this doesn't allow you to have functions share the same name if they have different signatures, as in your (open :: FS - File) example. To be honest, I think the C / Haskell approach of unambiguously-identified functions is clearly superior to the C++ / C# / Java class as namespace idiom, which has caused me no end of grief. Dynamic languages such as Python and Ruby, of course, can return anything from anywhere. This is nice in some cases, but having used both extensively I think (static typing+inference) is a better solution than dynamic typing. Now, in Haskell we have type inference, which is The Good Thing as it allows to validate your program at compile time. Hence, the idea coming up to my mind is that type inference actually forbids a type-directed resolution of names as in C++ or Java. Is this correct? Type inference and static typing are separate; inference makes static typing usable, but static typing makes compile-type correctness verification easier. And it's not inference making your goal impossible, but the fact that Haskell (like C) does not support arbitrary overloading. [1] http://www.mail-archive.com/haskell-cafe@haskell.org/msg64844.html [2] http://stackoverflow.com/questions/1897306/haskell-record-syntax-and-type-classes ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Name overloading
Hello John, Wednesday, January 13, 2010, 10:08:08 PM, you wrote: Of course, this doesn't allow you to have functions share the same name if they have different signatures class Open a where open :: a instance Open (Int - String) where ... instance Open (String - Int) where ... -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Name overloading
Well, you can get part of the way there, by using a class associated type class HasOpen a where type Open a :: * open :: a - Open a This lets you use type inference in one direction, without requiring that every result be a member of a data family. On the other hand, type inference just became directional, like in C#. you can't use the type of Open a to infer the type a because you've lost injectivity. You'd need a data type family to guarantee injectivity and determine a from the context of Open a, and that yields an ugly mess. Since each container would have to yield a distinct value type and interoperability goes out the window. On the other hand, the mixture of fixed type slots and type family slots gets you a pretty good compromise. You typically know the type of the structs whose members you are asking for. -Edward Kmett On Wed, Jan 13, 2010 at 2:08 PM, John Millikin jmilli...@gmail.com wrote: The usual suggestion I see for this sort of thing is to create a typeclass for the operations you care about[1][2]. For example: --- class HasOpen a where open :: a - Handle data DB data FS openDB :: DB - Handle openFS :: FS - Handle instance DB HasOpen where open = openDB instance FS HasOpen where open = openFS --- Of course, this doesn't allow you to have functions share the same name if they have different signatures, as in your (open :: FS - File) example. To be honest, I think the C / Haskell approach of unambiguously-identified functions is clearly superior to the C++ / C# / Java class as namespace idiom, which has caused me no end of grief. Dynamic languages such as Python and Ruby, of course, can return anything from anywhere. This is nice in some cases, but having used both extensively I think (static typing+inference) is a better solution than dynamic typing. Now, in Haskell we have type inference, which is The Good Thing as it allows to validate your program at compile time. Hence, the idea coming up to my mind is that type inference actually forbids a type-directed resolution of names as in C++ or Java. Is this correct? Type inference and static typing are separate; inference makes static typing usable, but static typing makes compile-type correctness verification easier. And it's not inference making your goal impossible, but the fact that Haskell (like C) does not support arbitrary overloading. [1] http://www.mail-archive.com/haskell-cafe@haskell.org/msg64844.html [2] http://stackoverflow.com/questions/1897306/haskell-record-syntax-and-type-classes ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Name overloading
On Wed, Jan 13, 2010 at 2:14 PM, Bulat Ziganshin bulat.zigans...@gmail.com wrote: class Open a where open :: a instance Open (Int - String) where ... instance Open (String - Int) where ... The problem with this approach is that you'll need to supply type annotations with basically every use of open, which is even more verbose than prepending the type name. -Edward Kmett ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
Colin Paul Adams wrote: Andrew It's weird that us Haskell people complain about there Andrew being only 26 letters in the alphabet Which alphabet? You have plenty of choice in Unicode. Er... I was under the impression that Haskell source code uses the ASCII character set, not Unicode. (And even if that's not the case, I've yet to find a way to type in the Unicode characters which are hypothetically possible.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
Marc Weber wrote: As you can see, this conclusively proves... something. What about brainfuck? 8 different signs are used. - http://de.wikipedia.org/wiki/Brainfuck#cite_note-0 The first link points to a page saying there is an interpreter 98 bytes in size.. What does this prove? :-) Exhibit A: The Iota calculus. It has one value (the Iota function), and one operator (function application). It is Turing-complete. I have literally *no idea* how big an interpretter would be... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Name overloading
Now, in Haskell we have type inference, which is The Good Thing as it allows to validate your program at compile time. Hence, the idea coming up to my mind is that type inference actually forbids a type-directed resolution of names as in C++ or Java. Is this correct? There is a proposed extension which is not implemented but was discussed on the list a while back, maybe you'd find this interesting: http://hackage.haskell.org/trac/haskell-prime/wiki/TypeDirectedNameResolution Search back in the archives for TDNR and you should turn up some threads. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On Jan 13, 2010, at 14:25 , Andrew Coppin wrote: Colin Paul Adams wrote: Andrew It's weird that us Haskell people complain about there Andrew being only 26 letters in the alphabet Which alphabet? You have plenty of choice in Unicode. Er... I was under the impression that Haskell source code uses the ASCII character set, not Unicode. The Report would beg to differ with you; see section 2.1. Haskell uses the Unicode [11] character set. However, source programs are currently biased toward the ASCII character set used in earlier versions of Haskell . (Currently at the time being 1998. Unicode is more prevalent these days.) (And even if that's not the case, I've yet to find a way to type in the Unicode characters which are hypothetically possible.) That's a problem with your editor/development environment. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
Brandon S. Allbery KF8NH wrote: On Jan 12, 2010, at 17:12 , Niklas Broberg wrote: Haskell '98 apparently features 25 reserved words. (Not counting forall and mdo and so on, which AFAIK are not in Haskell '98.) 21 actually. case, class, data, default, deriving, do, else, if, import, in, infix, infixl, infixr, instance, let, module, newtype, of, then, type, where. There's also three special words that can still be used as identifiers, so aren't reserved: as, qualified, hiding. Are we counting the FFI annex (foreign)? Strictly, wasn't that added *after* the Haskell 98 report was written? I.e., if you wanted to be ultra-technical about it, it's not part of the original Haskell '98? At any rate, no I didn't count the FFI. (Since I almost never use it.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On Jan 13, 2010, at 14:29 , Andrew Coppin wrote: Brandon S. Allbery KF8NH wrote: On Jan 12, 2010, at 17:12 , Niklas Broberg wrote: Haskell '98 apparently features 25 reserved words. (Not counting forall and mdo and so on, which AFAIK are not in Haskell '98.) 21 actually. case, class, data, default, deriving, do, else, if, import, in, infix, infixl, infixr, instance, let, module, newtype, of, then, type, where. There's also three special words that can still be used as identifiers, so aren't reserved: as, qualified, hiding. Are we counting the FFI annex (foreign)? Strictly, wasn't that added *after* the Haskell 98 report was written? I.e., if you wanted to be ultra-technical about it, it's not part of the original Haskell '98? That would be the import of annex, yes. It was not part of the original standard, but is considered part of the working Haskell '98 standard. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
sylvain wrote: Le mardi 12 janvier 2010 à 21:25 +, Andrew Coppin a écrit : Hi Andrew, As you can see, this conclusively proves... something. What, exactly? Not a lot. As you so elegantly point out, the number of keywords in a language is a fairly crude measurement of how complex the language is or is not. On the other hand, like lines of code, it's something that's easy to measure. ;-) Other such ways include taking the size of a gzip of a typical block of source code, like the Shootout does. This doesn't really prove anything though, because any benchmark can be implemented in more than one way. You could also try using how many pages it takes to explain the syntax of the language - but that also depends on how you explain it. Simplicity is really in the eye of the beholder, after all... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] What is the difference between Strachey diff from Scott Semantic Domain?
On Stack overflow page Conal Elliot says: Beware that denotational semantics has two parts, from its two founders Christopher Strachey and Dana Scott: the easier more useful Strachey part and the harder and less useful (for design) Scott part. http://stackoverflow.com/questions/1028250/what-is-functional-reactive-programming Any more information on how the Scott version is different from Starchey? On Tue, Jan 12, 2010 at 3:24 PM, Raoul Duke rao...@gmail.com wrote: http://lambda-the-ultimate.org/node/1665#comment-55086 http://perlustration.blogspot.com/ Daryoush ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
Brandon S. Allbery KF8NH wrote: On Jan 13, 2010, at 14:29 , Andrew Coppin wrote: Brandon S. Allbery KF8NH wrote: Are we counting the FFI annex (foreign)? Strictly, wasn't that added *after* the Haskell 98 report was written? I.e., if you wanted to be ultra-technical about it, it's not part of the original Haskell '98? That would be the import of annex, yes. It was not part of the original standard, but is considered part of the working Haskell '98 standard. Of course, you could always use Haskell 2010. It exists now, apparently... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
Brandon S. Allbery KF8NH wrote: On Jan 13, 2010, at 14:25 , Andrew Coppin wrote: Colin Paul Adams wrote: Andrew It's weird that us Haskell people complain about there Andrew being only 26 letters in the alphabet Which alphabet? You have plenty of choice in Unicode. Er... I was under the impression that Haskell source code uses the ASCII character set, not Unicode. The Report would beg to differ with you; see section 2.1. Haskell uses the Unicode [11] character set. However, source programs are currently biased toward the ASCII character set used in earlier versions of Haskell . (Currently at the time being 1998. Unicode is more prevalent these days.) So... how would GHC tell which of the hundreds of millions of possible character encodings is in use? (And even if that's not the case, I've yet to find a way to type in the Unicode characters which are hypothetically possible.) That's a problem with your editor/development environment. Or rather, the problem with every computer system known to man? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On 13 Jan 2010, at 22:25, Andrew Coppin wrote: Colin Paul Adams wrote: Andrew It's weird that us Haskell people complain about there Andrew being only 26 letters in the alphabet Which alphabet? You have plenty of choice in Unicode. Er... I was under the impression that Haskell source code uses the ASCII character set, not Unicode. (And even if that's not the case, I've yet to find a way to type in the Unicode characters which are hypothetically possible.) module Main where import Prelude hiding (putStrLn) import System.IO.UTF8 main = let é = Andrew Coppin снова оказался неправ ç = что_то_там where что_то_там = undefined in putStrLn é ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On Wed, Jan 13, 2010 at 12:55 AM, Eduard Sergeev eduard.serg...@gmail.comwrote: Andrew Coppin wrote: OK people, it's random statistics time! OK, my version of meaningless statistics: C++ (ISO/IEC 14882:1998(E)): 325 pages (712 including standard libraries) C# (ECMA-334): 505 pages (language only) Java: 450 pages (language only?) Scala (2.7): 125 pages (157 including standard library) Eiffel (ECMA-367): 160 pages (language only) ANSI SQL-92: 685 pages (language only) Haskell-98: 77 pages (247 including Prelude) Erlang (4.7.3) 162 pages (251 including builtin functions) Scheme (R5RS): 17 pages (45 including standard procedures) Oberon: 16 pages, including table of contents and Appendix (containing EBNF grammar). -- Sebastian Sylvan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On Jan 13, 2010, at 14:42 , Andrew Coppin wrote: Brandon S. Allbery KF8NH wrote: On Jan 13, 2010, at 14:25 , Andrew Coppin wrote: Colin Paul Adams wrote: Andrew It's weird that us Haskell people complain about there Andrew being only 26 letters in the alphabet Which alphabet? You have plenty of choice in Unicode. Er... I was under the impression that Haskell source code uses the ASCII character set, not Unicode. The Report would beg to differ with you; see section 2.1. Haskell uses the Unicode [11] character set. However, source programs are currently biased toward the ASCII character set used in earlier versions of Haskell . (Currently at the time being 1998. Unicode is more prevalent these days.) So... how would GHC tell which of the hundreds of millions of possible character encodings is in use? That's left to the compiler implementation. I'm not spotting an official statement in the GHC manual, but in practice GHC uses UTF-8. (It might support Windows standard UTF-16 as well; if do, it probably requires the first character of the source file to be a UTF-16 byte order mark.) (And even if that's not the case, I've yet to find a way to type in the Unicode characters which are hypothetically possible.) That's a problem with your editor/development environment. Or rather, the problem with every computer system known to man? s/man/you/ The existence of -XUnicodeSyntax ( http://www.haskell.org/ghc/docs/latest/html/users_guide/syntax-extns.html#unicode-syntax ) suggests that at least some other GHC users don't have your problem. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] wildcards for type variables?
On Jan 13, 2010, at 6:54 PM, Evan Laforge wrote: It's not a big issue, but it seemed like a nice symmetry with pattern matching syntax. And I don't think it's a weird idea. The Haskell dialect Curry [1] supports this syntax. Maybe the hurdle for Haskell is the competition with more complex, conflicting proposals like [2]. Sebastian [1] http://curry-language.org [2] http://hackage.haskell.org/trac/haskell-prime/wiki/PartialTypeSigs -- Underestimating the novelty of the future is a time-honored tradition. (D.G.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: what is *hack*?
Hi Michael, what is your experience with hack? Do you have any problem moving your apps from one server/env to another? Regards, titto 2010/1/13 Günther Schmidt gue.schm...@web.de: Hi Michael, on first impression this seems like a good idea then. Günther Am 13.01.10 15:48, schrieb Michael Snoyman: Günther, Hack is a layer between a web application and a web server. It allows you to write a web application once and have it communicate with the server in different ways simply by swapping the handler. For example, I have applications that I test on my local system using hack-handler-simpleserver and then deploy onto an Apache server using either hack-handler-cgi or hack-handler-fastcgi. Michael ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Pasqualino Titto Assini, Ph.D. http://quicquid.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
On Wed, Jan 13, 2010 at 1:28 PM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: On Jan 13, 2010, at 14:25 , Andrew Coppin wrote: (And even if that's not the case, I've yet to find a way to type in the Unicode characters which are hypothetically possible.) That's a problem with your editor/development environment. It's not just one's editor (I use emacs, and it's actually not that hard to type a decent subset of interesting Unicode characters in emacs with the tex input mode), but readability. The ASCII characters are universal and easily recognized (assuming you have a decent monochrome font); having to notice potentially significant differences involving diacritics alone (not to mention all the various mathematical symbols) in identifiers would drive me mad. It's the same reason we try to limit lines of code to ~80 characters — our editors are *capable* of more, sure, but are we? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: what is *hack*?
rack (and hack) permits also to concatenate applications (request handlers) one in top of the other. with interesting combinations (filters, encriptation layers, applications as such). It seems that this is the reason for its name. At first sight it seems too little code to make something useful, but it´s fine. 2010/1/13 Pasqualino Titto Assini tittoass...@gmail.com Hi Michael, what is your experience with hack? Do you have any problem moving your apps from one server/env to another? Regards, titto 2010/1/13 Günther Schmidt gue.schm...@web.de: Hi Michael, on first impression this seems like a good idea then. Günther Am 13.01.10 15:48, schrieb Michael Snoyman: Günther, Hack is a layer between a web application and a web server. It allows you to write a web application once and have it communicate with the server in different ways simply by swapping the handler. For example, I have applications that I test on my local system using hack-handler-simpleserver and then deploy onto an Apache server using either hack-handler-cgi or hack-handler-fastcgi. Michael ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Pasqualino Titto Assini, Ph.D. http://quicquid.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: what is *hack*?
Titto, I've had no problems with hack. The only things to keep in mind are outside the scope of hack such as: * Persistence. Clearly you need to optimize your application different for CGI run (load up only what you need right now) versus long-running processes like FastCGI (load data only once). * URL schemes. A lot of people assume that your web app with be served from the root of the domain. When using my simpleserver testing, that *is* the case. However, I deploy apps in subdirectories of my domain ( http://www.snoyman.com/photos/, http://www.snoyman.com/wordify/, etc), so I need to keep this in mind. My only two quips about hack itself is: * Versioning scheme. I wish (and have requested) that Hack would follow the Package Versioning Policy so that I could easily check for breaking changes. As is, I simply have to declare the exact version number of Hack I want to work with to guarantee my apps aren't broken in the future. * More serious issue is that it returns the response as a lazy bytestring. It's not really fair to call this a quip, since I fully supported this approach; nonetheless, using an enumerator for this would probably be more efficient for certain use cases. I just a few hours ago sent off an e-mail about bringing into fruition the Web Application Interface for Haskell, which I would envision as Hack with these two quips addressed. Theoretically, it would also allow easy collaboration with Hack. Michael On Wed, Jan 13, 2010 at 10:33 PM, Pasqualino Titto Assini tittoass...@gmail.com wrote: Hi Michael, what is your experience with hack? Do you have any problem moving your apps from one server/env to another? Regards, titto 2010/1/13 Günther Schmidt gue.schm...@web.de: Hi Michael, on first impression this seems like a good idea then. Günther Am 13.01.10 15:48, schrieb Michael Snoyman: Günther, Hack is a layer between a web application and a web server. It allows you to write a web application once and have it communicate with the server in different ways simply by swapping the handler. For example, I have applications that I test on my local system using hack-handler-simpleserver and then deploy onto an Apache server using either hack-handler-cgi or hack-handler-fastcgi. Michael ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Pasqualino Titto Assini, Ph.D. http://quicquid.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc -e
On Wed, 6 Jan 2010, Gwern Branwen wrote: On Wed, Jan 6, 2010 at 7:23 PM, Tony Morris tonymor...@gmail.com wrote: ghc -e import Control.Monad; forM [[1,2,3]] reverse As of 6.10.2, the bug whereby the GHC API lets you use functions from anywhere just by naming them (Java-style) has not been fixed: $ ghc -e Control.Monad.forM [[1,2,3]] reverse package flags have changed, resetting and loading new packages... Why is this a bug? This is the intended behaviour in GHCi and you can include and exclude packages with -package and -hide-package options, respectively. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: looking for origin of quote on preprocessors and language design
Maciej Piechotka schrieb: Not quite. While I agree that the *frequent* need for a preprocessor shows omissions in (the design of) a language. it is not necessary the case. Preprocessor may be useful if: - there is a new beatyful feature in newer version of compiler but you still want to have backward compatibility. - there are compiler or platform dependant elements. For example if you write a driver in Haskell you may want to share code as much as possible but you need to know 1) the size of registers and 2) the platform you're writing as Windows have quite different API then Linux or BSD. - You need to enable/disable features at build-time. It is not frequent at closed-source system but it is frequent on OpenSource systems. For example I might need to have minimal program for embedded system but with full feature set it likly conquer the desktops Many of these problems are solved by preprocessor intervention in C/C++, but there is often no need to do so. You could also write system dependent modules, where the right module for your system is included by the build system. I hope the build system does not count as a preprocessor. In Haskell it is however still no fun to support multiple versions of the base libraries, not to speak of different compilers - and their set of libraries. Unfortunately, the original question is still not answered. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: status of wash?
Hi, well I followed klondykes advise and followed through with the examples on the http://www.haskell.org/haskellwiki/Practical_web_programming_in_Haskell site. The authors did point out at the very beginning that the approach shown was not very sophisticated and I'd agree with that :) . Of what I *read* about WASH that is more like what I had in mind, state of the art sort of thing. How come it's discontinued or not maintained? It pretty much looks like Seaside just in Haskell. As I said this is by judging from what I *read*, I haven't actually used it yet. Is this technique continued in some other project maybe? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: looking for origin of quote on preprocessors and language design
On Wed, 2010-01-13 at 22:42 +0100, Henning Thielemann wrote: Maciej Piechotka schrieb: Not quite. While I agree that the *frequent* need for a preprocessor shows omissions in (the design of) a language. it is not necessary the case. Preprocessor may be useful if: - there is a new beatyful feature in newer version of compiler but you still want to have backward compatibility. - there are compiler or platform dependant elements. For example if you write a driver in Haskell you may want to share code as much as possible but you need to know 1) the size of registers and 2) the platform you're writing as Windows have quite different API then Linux or BSD. - You need to enable/disable features at build-time. It is not frequent at closed-source system but it is frequent on OpenSource systems. For example I might need to have minimal program for embedded system but with full feature set it likly conquer the desktops Many of these problems are solved by preprocessor intervention in C/C++, but there is often no need to do so. You could also write system dependent modules, where the right module for your system is included by the build system. I hope the build system does not count as a preprocessor. In Haskell it is however still no fun to support multiple versions of the base libraries, not to speak of different compilers - and their set of libraries. Unfortunately, the original question is still not answered. Hmm. May I ask how to do for example something depending on POSIX or WinAPI? I am sorry but I cannot see how any of the above problems could be solved. Regards signature.asc Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] looking for origin of quote on preprocessors and language design
Haskell doesn't *need* preprocessors, but they sure make a lot of things easier. There are three I use regularly (c2hs, cpphs, noweb), and each serves a purpose which isn't directly supported by plain Haskell: c2hs -- Supports generating foreign function imports and wrappers based on C header files. This is simpler and less prone to cross-platform type errors than writing the declarations in Haskell, which generally requires a cpp-style #if..#else..#endif preprocessor anyway. cpphs -- The C preprocessor, adapted to Haskell syntax. I'd like to replace my uses of it with Template Haskell, but TH's limitation that its splices can't be defined in the same file make it (for my purposes) essentially useless. cpphs is text-based, which means you can glue together pretty much anything and let the compiler verify that it type-checks. noweb -- True literate programming (as opposed to .lhs verbose commenting), which allows sections of the source code to be re-arranged arbitrarily. I suppose it's possible in theory for a language to support this without a preprocessing step, but (to my knowledge) not even LISP derivatives do/can. On Thu, Jan 7, 2010 at 04:32, Johannes Waldmann waldm...@imn.htwk-leipzig.de wrote: Dear all, It's not exactly Haskell-specific, but ... I am trying to track down the origin of the proverb the existence (or: need for) a preprocessor shows omissions in (the design of) a language. I like to think that in Haskell, we don't need preprocessors since we can manipulate programs programmatically, because they are data. In other words, a preprocessor realizes higher order functions, and you only need this if your base language is first-order. Yes, that's vastly simplified, and it does not cover all cases, what about generic programming (but this can be done via Data.Data) and alex/happy (but we have parsec) etc etc. Best regards, J.W. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to fulfill the code-reuse destiny of OOP?
Anonymous classes in Java close over their lexical environment (can refer to variables in that lexical environment, with values bound at the time of instance construction) with the caveat that only local variables/parameters marked as 'final' may be referred to. Aside from the horrible syntax, this is the key distinction between them, and, say, Ruby closures. Referring to mutable variables from inside a closure has its drawbacks, making the horrible syntax the biggest stumbling block to using them IMHO (other than runtime overhead, which I believe is also an issue). Yes, this. Which makes them basically unusable where you might want proper closures. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Web application interface
The hyena backend is essentially just a translator between hack and wai, i failed to finished it since I can't understand iteratee (seriously) and eventually got distracted ... What hyena tries to solve can't be realized in hack, so there's not too much reason for a backend anyway. Hyena is especially tuned for streaming and that's exactly what hack can't do (in practice). http://github.com/nfjinjing/hack-handler-hyena -- jinjing ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] space leaks and optimizations
On Sat, Jan 9, 2010 at 2:23 AM, Alexei Kitaev kit...@iqi.caltech.edu wrote: Reading the discussion related to your blog, I realized that strict State is different in that it does not actually force the state. But forcing can be achieved by wrapping all actions with the following function: sState :: (s - (a,s)) - State s a sState f = State $ \s - case f s of (a,s') - s' `seq` (a,s') I hope that somebody will answer my other questions about the operational semantics and optimizations. Hi Alexei, you have a ton of great points but I wanted to discuss an issue with this one. It's unusual that this is what you want either; since it only reduces the state to WHNF. For example, if your state is a string, this only evaluates enough to know whether or not the string is empty at each step, and you can still get into trouble with code like this: put (xxx ++ some_bad_computation) which leave bottoms inside of your state which won't show up until later. Several attempts to solve this problem exist, but the most commonly used one is the rnf strategy from Control.Parallel.Strategies, which uses a typeclass to allow each type to specify how to evaluate itself completely. -- ryan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] FFI, C/C++ and undefined references
Bulat, Some very good suggestions. I will try to appease Ceiling Cat and reduce my (perhaps gratuitous) use of unsafePerformIO. I'm going to have to use it somewhere, since I want referentially transparent code (and I try to avoid the IO monad when possible, anyway). 2. if your function returns Ptr a - then hold in haskell types this Ptr a. no need to convert it back and forth to ForeignPtr Yes, I thought of doing this, but then thought it was better to use a so-called managed foreign pointer via newForeignPtr. I thought this was the best way to have a foreign pointer that the Haskell garbage collector would eat up when it was no longer in use. I could be wrong. I convert from a ForeignPtr to a Ptr, because the FFI code wasn't compiling at all (nevermind the missing C/C++ reference problem), as apparently a ForeignPtr isn't the sort of thing that an imported foreign function can take as an argument (or so said GHC). I just assumed that the back-and-forth between Ptr and ForeignPtr would be compiled away by GHC. I could be wrong, though. If performance starts to suffer, I'll manage the Ptr memory in my code directly. 4. i don't looked in your code but if C functions defines *modifiable* datastructure - you should use it at Haskell side via imperatiove functions, i.e. those with return type IO a. using unsafePerformIO in this case will lead to Haskell compiler will consider this datatype as permanent and reorder operations on the will Good point. I would do this if I planned to train or update the language model from within Haskell, but, as it stands, I just want to train it once (at the command line, using the built-in mechanisms of SRILM) and then read in the ARPA-formatted language model file for use in Haskell. 3. why c_dlm is FunPtr in your definition? it should be foreign import ccall srilm.h deleteLM c_dlm :: Ptr Ngram - IO () No reason. Just because I don't know what I'm doing yet. Thanks for the correction. Thanks for the help, Bulat. Much appreciated. Best, Dennis -- View this message in context: http://old.nabble.com/FFI%2C-C-C%2B%2B-and-undefined-references-tp27139612p27156139.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] FFI, C/C++ and undefined references
Malcolm, I saw this suggestion somewhere else. Unfortunately, it didn't help either. I still get the undefined reference errors. I did eventually get ghc to compile Main.hs by putting the -c and -cpp flags after --make Main.hs. Then it produces a Main.o file which (even with +x permissions on my Linux box) will not run. I just get the message cannot run binary file, or some such message. No explanation given. Any ideas? Best, Dennis Malcolm Wallace wrote: But when I try to compile it (after having successfully compiled the C code with g++), I get: $ ghc --make Main.hs You are not telling ghc to link against the C/C++ code, e.g. ghc --make Main.hs srilm.o Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://old.nabble.com/FFI%2C-C-C%2B%2B-and-undefined-references-tp27139612p27156254.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] FFI, C/C++ and undefined references
Sorry. In my haste to paste in the .c file, I left out all the include statements. I do have #include srilm.h there (which to my non- C/C++ mind seems stupid -- why the hell would you need to import the header file for the code that it's a header *for*?) Still no dice. Thanks for your time, though. Sorry to waste it. --D.N. -- View this message in context: http://old.nabble.com/FFI%2C-C-C%2B%2B-and-undefined-references-tp27139612p27156267.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] FFI, C/C++ and undefined references
On Jan 13, 2010, at 23:28 , DNM wrote: Sorry. In my haste to paste in the .c file, I left out all the include statements. I do have #include srilm.h there (which to my non- C/C++ mind seems stupid -- why the hell would you need to import the header file for the code that it's a header *for*?) Really, the only reason in this case is that there is no equivalent for `extern C' that you can apply to a function definition, only to a declaration. The rationale is that everything that works with the function, including its definition, needs to see that declaration, so rather than repeat it in the definition you #include the declaration. In GHC, this is the kind of thing that lands in the .hi file; the tradeoff is you need to have up to date .hi files for everything that needs to see that information, which can lead to dependency loops. GHC has a .hs-boot hack to work around this. No free lunch -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Language simplicity
Tom == Tom Tobin korp...@korpios.com writes: Tom readability. The ASCII characters are universal and easily Tom recognized No they are not. My wife is Chinese. When she was learning pinyin as a child, she asked her father for help with some homework. He replied that he didn't understand them. -- Colin Adams Preston Lancashire ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Strategies
Dear Ryan, Thanks a lot for your support and for pointing out a problem with my approach to forcing the state. I was aware of this issue but I didn't know there was a standard solution. It is indeed very natural to let each type specify how to evaluate itself. I will try this technique on the nearest occasion. Incidentally, the link to Control.Parallel.Strategies from the latest GHC User Guide is broken... --Alexei Ryan Ingram wrote: On Sat, Jan 9, 2010 at 2:23 AM, Alexei Kitaev kit...@iqi.caltech.edu wrote: Reading the discussion related to your blog, I realized that strict State is different in that it does not actually force the state. But forcing can be achieved by wrapping all actions with the following function: sState :: (s - (a,s)) - State s a sState f = State $ \s - case f s of (a,s') - s' `seq` (a,s') I hope that somebody will answer my other questions about the operational semantics and optimizations. Hi Alexei, you have a ton of great points but I wanted to discuss an issue with this one. It's unusual that this is what you want either; since it only reduces the state to WHNF. For example, if your state is a string, this only evaluates enough to know whether or not the string is empty at each step, and you can still get into trouble with code like this: put (xxx ++ some_bad_computation) which leave bottoms inside of your state which won't show up until later. Several attempts to solve this problem exist, but the most commonly used one is the rnf strategy from Control.Parallel.Strategies, which uses a typeclass to allow each type to specify how to evaluate itself completely. -- ryan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: FASTER primes
Daniel Fischer daniel.is.fischer at web.de writes: Am Mittwoch 13 Januar 2010 10:43:42 schrieb Heinrich Apfelmus: I wonder whether it's really the liveness of pair in mergeSP (a,b) pair = let sm = spMerge b (fst pair) in (a ++ fst sm, merge (snd sm) (snd pair)) that is responsible for the space leak, for chances are that Sparud's technique applies and pair is properly disposed of. Rather, it could be that we need the stronger property that forcing the second component will evaluate the first to NF. I think that is responsible. At least that's how I understand the core: mergeSP (a,b) ~(c,d) = (a ++ bc, merge b' d) where (bc, b') = spMerge b c spMerge ... That is equivalent to first (a++) . second (`merge`d) $ spMerge b c and Daniel's fix is equivalent to first (a++) $ spMerge b c d Now, when compiler sees the first variant, it probably treats spMerge as opaque. I.e. although in reality spMerge only contributes to the first channel while it is progressively instantiated, and (`merge`d) will only be called upon when spMerge's final clause is reached, that is (most likely) not known to the compiler at this stage. When looking at just the first expression itself, it has to assume that spMerge may contribute to both channels (parts of a pair) while working, and so can't know _when_ /d/ will get called upon to contribute to the data, as it is consumed finally at access. So /d/ is gotten hold of prematurely, _before_ going into spMerge. The second variant passes the responsibility for actually accessing its inputs to spMerge itself, and _it_ is clear about needing /d/ only in the very end. Just a theory. :) Does that make sense? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] FFI, C/C++ and undefined references
Hello DNM, Thursday, January 14, 2010, 7:07:43 AM, you wrote: Yes, I thought of doing this, but then thought it was better to use a so-called managed foreign pointer via newForeignPtr. i recommend to use Ptr and switch to ForeignPtr only when you will study how to use it. overall, unsafe* functions are really unsafe, and using them without learning will lead to mysterious problems. it's like painting with eyes closed Good point. I would do this if I planned to train or update the language model from within Haskell, but, as it stands, I just want to train it once (at the command line, using the built-in mechanisms of SRILM) and then read in the ARPA-formatted language model file for use in Haskell. you may add problems by using unsafePerformIO. i recommend you to learn first how to manage FFI without it, make program work, and only then try to use it. eat elephant in small pieces! look into http://haskell.org/haskellwiki/IO_inside -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] FFI, C/C++ and undefined references
Hello Brandon,
Thursday, January 14, 2010, 7:40:45 AM, you wrote:
Really, the only reason in this case is that there is no equivalent
for `extern C' that you can apply to a function definition, only to
a declaration
it works with GCC:
extern C int c_szOpenArchive (TABI_ELEMENT* params)
{
}
--
Best regards,
Bulatmailto:bulat.zigans...@gmail.com
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