[Haskell-cafe] Problems translating Conor McBride's talk into Haskell + DataKind + KindPoly
Most part of Conor's talk at ICFP, until just before the last stage
where he heavily uses true value dependency for compiler correctness all
the code seemed to be able to translate into Haskell with the new hot
DataKinds and PolyKinds extension.
I tried it in GHC 7.4.1 and it was possible to do it, but I got stuck
and I had to make the generic list structure mono-kinded with kind
signatures rather not use the PolyKinds extension.
I wonder if this is just a but of GHC 7.4.1's implementation of
PolyKinds, or a limitation of the DataKind design.
I attached a literate Haskell script with this message that illustrates
this problem.
Thanks in advance for any comments including whether it runs in later
versions or still has problems, and discussions about the DataKinds and
PolyKinds extension.
Ki Yung
I ran into problems when I tryed doing some of
the Conor's talk at ICFP 2012 in Haskell with
DataKinds and PolyKinds extension, using GHC 7.4.1.
I am wondering whether this is a bug in GHC 7.4.1
(maybe fixed in GHC 7.6.x? haven't tried since
I haven't installed 7.6.x yet), or a limitation of
datatype promotion itself. The problem happens when
I try to use promoted list datatype.
Here is a code that illustrates this problem:
{-# LANGUAGE GADTs, DataKinds, PolyKinds, KindSignatures #-}
data GList x i j where
GNil :: GList x i i
GCons :: x i j - GList x j k
- GList x i k
append :: GList x i j - GList x j k
- GList x i k
append GNilys = ys
append ( GCons x xs) ys =
GCons x (append xs ys)
Instantiating to a plain regular list works
data Elem a i j where
MkElem :: a - Elem a () ()
type List' a = GList (Elem a) () ()
nil' = GNil {-~-} :: List' a
cons' :: a - List' a - List' a
cons' = GCons . MkElem
Instantiating to a length indexed list works
data Nat = Z | S Nat
data ElemV a i j where
MkElemV :: a - ElemV a (S n) n
type Vec a n = GList (ElemV a) n Z
vNil = GNil {-~-} :: Vec a Z
vCons :: a - Vec a n - Vec a (S n)
vCons = GCons . MkElemV
Good, then let's do some more things with DataKinds.
Promoting Bool works as well as Nat.
data RelB :: Bool - Bool - * where
MkRelB :: RelB b b
l1 = GCons MkRelB GNil
But, I have some problems with promoting [Bool] !!!
data RelBL :: [Bool] - [Bool] - * where
MkRelBL :: RelBL bs bs
I can only with mono-kinded list structure.
Below is a momomorphization of GList.
data MyList (x :: [Bool] - [Bool] - *) i j where
MyNil :: MyList x i i
MyCons :: x i j - MyList x j k
- MyList x i k
l3 = MyCons MkRelBL MyNil
However when I try to do this with the poly-kinded GList,
I get a kind error. Is this a bug of GHC 7.4.1 or is this
a limitation of DataKind extension?
l4 = GCons MkRelBL GNil
tmp.lhs:74:22:
Couldn't match kind `BOX' against `*'
Kind incompatibility when matching types:
k0 :: BOX
[Bool] :: *
In the second argument of `GCons', namely `GNil'
In the expression: GCons MkRelBL GNil
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Re: [Haskell-cafe] Problems translating Conor McBride's talk into Haskell + DataKind + KindPoly
Promotion works for user defined lists such as data List a = Nil | Cons a (List a) And, if I use (List Bool) instead of [Bool] everything works out. It's only the Haskell list type constructor [] is being a problem. In the Giving Haskell a promotion paper, it says that Haskell lists are natively promoted. I believe this means that it is treated specially somehow. I don't know how it is implemented but what GHC 7.4.1 does specially for Haskell lists has some problems. So, it's clearly not a limitation of DataKind and PolyKind extension, but that special routine for [] is the issue. I might have to write bug report. On 2012년 10월 25일 18:07, Ahn, Ki Yung wrote: Most part of Conor's talk at ICFP, until just before the last stage where he heavily uses true value dependency for compiler correctness all the code seemed to be able to translate into Haskell with the new hot DataKinds and PolyKinds extension. I tried it in GHC 7.4.1 and it was possible to do it, but I got stuck and I had to make the generic list structure mono-kinded with kind signatures rather not use the PolyKinds extension. I wonder if this is just a but of GHC 7.4.1's implementation of PolyKinds, or a limitation of the DataKind design. I attached a literate Haskell script with this message that illustrates this problem. Thanks in advance for any comments including whether it runs in later versions or still has problems, and discussions about the DataKinds and PolyKinds extension. Ki Yung ___ 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 Create Programming Language with Haskell?
Don't think this is what Shogo is looking for since the book is not about implementing a language WITH Haskell, but how to implement Haskell like languages with a more low level language (like C). 2011년 11월 16일 00:13, Anton Kholomiov 쓴 글: This can be very helpful: Implementation of FP languages by Simon Peyton Jones http://research.microsoft.com/en-us/um/people/simonpj/papers/slpj-book-1987/index.htm 2011/11/16 Shogo Sugamoto eseh...@gmail.com mailto:eseh...@gmail.com Hi,Cafe. I want to create my own Programming Language with Haskell, and I learn how to do it. I read: WikiBooks of Write Yourself a Scheme in 48 Hours, Real World Haskell of Chapter Using Parsec, Source of HJS, Book of Introduction of Functional Programming Using Haskell. Ok,What is another good source creating my own Programming Language with Haskell? Thanks :) esehara ___ 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Consuming anyToken with parsing with derivatives (derp) library in Hackage?
I was playing with derp recently, and many of the Char and Combinator of Parsec seem to be easily definable from derp. However, I haven't yet figured out a natural way to define anyToken or satisfy combiator of Parsec using derp. There is a way of course, to list all the unicode characters and combine them with |, which is extremely inefficient, even if you limit yourself that satisfy combinator be compile time template haskell function, it still seems a bit silly. For things like space, it seems reasonable to list all take the sum of them, since there are handful of them. But things like consume anything that is not a space ought to be defined as a complement or negation of the space parser. In general CFG is not closed under negation, but most of the time what we want to take a negation is really for regular fragment of the language, like consuming anything that is not a linebreak to lex/parse one line comments. In Matt's Standford talk, he mentioned some vision about going beyond CFG and he mentioned negation, but in the library implementation I didn't find that. Is it already possible with some trick? Is there a standard way to define such combinators with derp? Or, is it the case that there a way to do it in the scheme library but not implemented in Haskell derp package? I read through the scheme implementation too but there didn't seem to be a combinator for tacking negations either. Ki Yung Ahn ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Best links for Haskell Platform distro packages?
2010년 07월 17일 16:53, Don Stewart 쓴 글: Can distro maintainers confirm these are the best links for each distro package? Debian http://packages.debian.org/squeeze/haskell-platform (or should it be sid?) http://packages.debian.org/haskell-platform I am not a maintainer but I suggest the link above since it is the way to have them both, by searching package by package name. I believe haskell-platform package name is not likely to change. So, that URL will consistently serve the purpose even after major stable releases. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] wxHaskell not able to link to libstdc++.so
Dear Haskellers, I heard from a guy who was having problems with wxHaskell using GHC 6.10.x. I tried it myself and had the exact same problem occurring using GHC 6.12.x as well. I am using the debian unstable version of ghc6 package. kya...@kyagrd:~/tmp$ head bb.hs import Graphics.UI.WX import Graphics.UI.WXCore (bitmapGetSize) main = start viewer viewer :: IO () viewer = do bm - bitmapCreateFromFile ~/sample.jpg size - bitmapGetSize bm f - frame [text := viewer, on paint := onPaint bm, clientSize :=size] kya...@kyagrd:~/tmp$ runghc bb.hs bb.hs: command line: can't load .so/.DLL for: stdc++ (libstdc++.so: cannot open shared object file: No such file or directory) kya...@kyagrd:~/tmp$ ghc bb.hs bb.o: In function `r43M_info': (.text+0x48): undefined reference to `wxzm0zi12zi1zi4_GraphicsziUIziWXziWindow_zdfDimensionsObject_closure' bb.o: In function `r43O_info': (.text+0xa8): undefined reference to `wxzm0zi12zi1zi4_GraphicsziUIziWXziWindow_zdfPaintObject_closure' ... The problem is there is no libstdc++.so in my Debian system as well as the guy who uses Ubunto. What exists is libstdc++.so.6. kya...@kyagrd:~/tmp$ ls /usr/lib/libstdc++.* /usr/lib/libstdc++.so.6@ /usr/lib/libstdc++.so.6.0.13 I wonder how wxHaskell was even able to successfully configure and compile at all. I didn't have wx package installed before, and I installed it just today and it successfully configured and compiled but unable to dynamically link to libstdc++.so. More serious problem is that wxHaskell doesn't work even making a symbolic link of libstdc++.so from libstdc++.so.6. I've also tried running ldconfig -v and ldconfig -p as a root, but still get the same problem. Is this a commom problem with the libraries linking to libstdc++.so or is this just the wxHaskell problem? Or, is this a ghc problem? -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: wxHaskell not able to link to libstdc++.so
Just searched and found out that this is a ticket 4 months old http://hackage.haskell.org/trac/ghc/ticket/3798 but it seems that it's not only a GHCi problem. It doesn't compile with ghc either. 2010년 04월 22일 17:05, Ahn, Ki Yung 쓴 글: Dear Haskellers, I heard from a guy who was having problems with wxHaskell using GHC 6.10.x. I tried it myself and had the exact same problem occurring using GHC 6.12.x as well. I am using the debian unstable version of ghc6 package. kya...@kyagrd:~/tmp$ head bb.hs import Graphics.UI.WX import Graphics.UI.WXCore (bitmapGetSize) main = start viewer viewer :: IO () viewer = do bm- bitmapCreateFromFile ~/sample.jpg size- bitmapGetSize bm f- frame [text := viewer, on paint := onPaint bm, clientSize :=size] kya...@kyagrd:~/tmp$ runghc bb.hs bb.hs:command line: can't load .so/.DLL for: stdc++ (libstdc++.so: cannot open shared object file: No such file or directory) kya...@kyagrd:~/tmp$ ghc bb.hs bb.o: In function `r43M_info': (.text+0x48): undefined reference to `wxzm0zi12zi1zi4_GraphicsziUIziWXziWindow_zdfDimensionsObject_closure' bb.o: In function `r43O_info': (.text+0xa8): undefined reference to `wxzm0zi12zi1zi4_GraphicsziUIziWXziWindow_zdfPaintObject_closure' ... The problem is there is no libstdc++.so in my Debian system as well as the guy who uses Ubunto. What exists is libstdc++.so.6. kya...@kyagrd:~/tmp$ ls /usr/lib/libstdc++.* /usr/lib/libstdc++.so.6@ /usr/lib/libstdc++.so.6.0.13 I wonder how wxHaskell was even able to successfully configure and compile at all. I didn't have wx package installed before, and I installed it just today and it successfully configured and compiled but unable to dynamically link to libstdc++.so. More serious problem is that wxHaskell doesn't work even making a symbolic link of libstdc++.so from libstdc++.so.6. I've also tried running ldconfig -v and ldconfig -p as a root, but still get the same problem. Is this a commom problem with the libraries linking to libstdc++.so or is this just the wxHaskell problem? Or, is this a ghc problem? -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Is cabal option --extra-lib-dirs working?
I had some problem with --extra-lib-dirs option in cabal-install. I've been trying installing bindings-yices package on hackage. Since yices may be installed in non-standard location, such as under your own home directory, one may have to use --extra-include-dirs and --extra-lib-dirs option. --extra-include-dirs work well and locates the header for the yices C binding, but --extra-lib-dirs option does not seem to work well. Would this be a cabal-install bug, or some package misconfiguration? kya...@kyavaio:~/tmp/bindings-yices-0.1$ cabal configure Resolving dependencies... Configuring bindings-yices-0.1... cabal: Missing dependency on a foreign library: * Missing header file: yices_c.h * Missing C library: yices This problem can usually be solved by installing the system package that provides this library (you may need the -dev version). If the library is already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where it is. kya...@kyavaio:~/tmp/bindings-yices-0.1$ cabal configure --extra-include-dirs=/home/kyagrd/yices-1.0.21/include Resolving dependencies... Configuring bindings-yices-0.1... cabal: Missing dependency on a foreign library: * Missing C library: yices This problem can usually be solved by installing the system package that provides this library (you may need the -dev version). If the library is already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where it is. kya...@kyavaio:~/tmp/bindings-yices-0.1$ cabal configure --extra-include-dirs=/home/kyagrd/yices-1.0.21/include --extra-lib-dirs=/home/kyagrd/yices-1.0.21/lib Resolving dependencies... Configuring bindings-yices-0.1... cabal: Missing dependency on a foreign library: * Missing C library: yices This problem can usually be solved by installing the system package that provides this library (you may need the -dev version). If the library is already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where it is. kya...@kyavaio:~/tmp/bindings-yices-0.1$ kya...@kyavaio:~/tmp/bindings-yices-0.1$ ls /home/kyagrd/yices-1.0.21/include/ yices_c.h yicesl_c.h kya...@kyavaio:~/tmp/bindings-yices-0.1$ ls /home/kyagrd/yices-1.0.21/lib/ libyices.a libyices.so kya...@kyavaio:~/tmp/bindings-yices-0.1$ ls -al /home/kyagrd/yices-1.0.21/include/ 합계 40 drwxr-xr-x 2 kyagrd kyagrd 4096 2009-07-17 20:58 . drwxr-xr-x 6 kyagrd kyagrd 4096 2009-07-07 23:19 .. -rw-r--r-- 1 kyagrd kyagrd 27948 2009-05-05 19:03 yices_c.h -rw-r--r-- 1 kyagrd kyagrd 1786 2009-05-05 19:03 yicesl_c.h kya...@kyavaio:~/tmp/bindings-yices-0.1$ ls -al /home/kyagrd/yices-1.0.21/lib/ 합계 8936 drwxr-xr-x 2 kyagrd kyagrd4096 2009-12-30 19:29 . drwxr-xr-x 6 kyagrd kyagrd4096 2009-07-07 23:19 .. -rw-r--r-- 1 kyagrd kyagrd 5167710 2009-05-05 19:03 libyices.a -rwxr-xr-x 1 kyagrd kyagrd 3955648 2009-05-05 19:03 libyices.so ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Haskell for Physicists
ed...@ymonad.com 쓴 글: Hi, I will give a seminar to physicists at USP (Universidade de São Paulo, Brazil) university and they asked me for a good title, something that can attract physicists. Anyone has some suggestions? (Will be a seminar about the use of Haskell to substitute C or Fortran in a lot of tasks, and how it can be used in some problems instead of Matlab, Mathematica, etc.) Thanks, Edgar You should also see the well known Haskell story in this area: http://bayern.stanford.edu/~brant/lightning/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Testing nested implication properties with QuickCheck?
How should I you use QuickCheck for testing a property that is a nested implecation such as (A == B) == C ? The problem is (==) in QuickCheck is that its type is Testable prop = Bool - prop - Property rather than Testable prop = prop - prop - Property. So, A == (B == C) would work but (A == B) == C won't work when A, B, C are boolean expressions. Is there some trick to handle the latter? Thanks, -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Testing nested implication properties with QuickCheck?
How should I use QuickCheck for testing a property that is a nested implecation such as (A == B) == C ? The problem is (==) in QuickCheck is that its type is Testable prop = Bool - prop - Property rather than Testable prop = prop - prop - Property. So, A == (B == C) would work but (A == B) == C won't work when A, B, C are boolean expressions. Is there some trick to handle the latter? Thanks, -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: A Question of Restriction
Brian Troutwine wrote: Hello all. I would like to define a data type that is the super-set of several types and then each of the proper subset types. For example: data Foo = One | Two | Three | Four data Odd = One | Three data Even = Two | Four This, of course, does not work. It seems that such a thing should possible to express entirely in the type system, but I cannot think of how. Would someone be so kind as to explain how this sort of thing can be accomplished? You might want to look at Johan Nordlander's O'Haskell. It's a dialect of Haskell with such subtyping, designed and implemented while ago. Recently there was a proposal (but not an implementation yet) of subtyping data types in general with recursion and including GADTs http://portal.acm.org/citation.cfm?id=1411286.1411297 (I want to work on this again some time later again). But neither of these work is not implemented as an extension feature in major Haskell implementations like GHC or Hugs. I want to push this work further some time later on. FYI, there exist a functional language which you can express this kind of idea though. For example, in OCaml, you can use polymorphic variants. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Goldman Sachs - your home for OCaml and Erlang?
Max Cantor wrote: I know that this is a bit off topic, but thought it would interest several readers. Apparently, GS, which. AFAIK, doesn't make a lot of noise in the FP space compared to some other banks, does use some FP: http://www.zerohedge.com/article/aleynikov-code-dump-uncovered The link you gave seems controversial. But there is a more relative product based on OCaml that GS actually uses (or have used): http://www.lexifi.com/press_2002-09-02.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Haskell as a first language?
Before teaching any data structure course, one MUST learn functional languages with ADTs. It makes everything so easy to understand. So, it MUST be a first language in every institution. The biggest reason that one should learn functional languages with algebraic data type(ADT)s first is because understanding recursive definitions. If you recursion first, understanding iteration and mutable data structures are dead simple and easy: they are just alternate representation or optimization. However, when you learn while loops and for loops first, your brain gets damaged and a lot of students gets stuck when they first see the Tower of Hanoi, the notorious in-place quicksort routine written in imperative languages, you'll get to think of recursion as some stack blowing up monster that must be unrolled and managed manually. Furthermore, learning data structures in most traditional imperative language literature gives you the impression that linked list and binary trees are brain-fucking spaghetti monsters of memory pointers all the cells, which is a dead simple recursive definition in functional languages with ADTs. Personally, I never really understood what linked list was before I learned ML and Haskell, although I've used doubly linked list in a C++ standard library, which was to me a black box that meets the specification in some huge standard document, for two years. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Flipping *-*-* kinds, or monadic finally-tagless madness
Kim-Ee Yeoh wrote: The add function illustrates the kind of do-sugaring we know and love that I want to use for Symantics. lam f = unZ $ do show_c0 - get let vname = v ++ show_c0 c0 = read show_c0 :: VarCount c1 = succ c0 fz :: Z a String - Z b String fz = Z . f . unZ put (show c1) s - (fz . return) vname return $ (\\ ++ vname ++ - ++ s ++ ) Now with lam, I get this cryptic error message (under 6.8.2): Occurs check: cannot construct the infinite type: b = a - b When trying to generalise the type inferred for `lam' Signature type: forall a1 b1. (Y String a1 - Y String b1) - Y String (a1 - b1) Type to generalise: forall a1 b1. (Y String a1 - Y String b1) - Y String (a1 - b1) In the instance declaration for `Symantics (Y String)' Both the two types in the error message are identical, which suggests no generalization is needed. I'm puzzled why ghc sees an infinite type. Any ideas on how to proceed? Not an answer, but just a different error message from GHC 6.10.3 when I tried loading up your code. kya...@kyavaio:~/tmp$ ghci EvalTaglessF.hs GHCi, version 6.10.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( EvalTaglessF.hs, interpreted ) EvalTaglessF.hs:264:14: Couldn't match expected type `b1' against inferred type `b' `b1' is a rigid type variable bound by the type signature for `fz' at EvalTaglessF.hs:263:31 `b' is a rigid type variable bound by the type signature for `lam' at EvalTaglessF.hs:248:26 Expected type: Z b1 String Inferred type: Z b String In the expression: Z . f . unZ In the definition of `fz': fz = Z . f . unZ EvalTaglessF.hs:264:22: Couldn't match expected type `a1' against inferred type `a' `a1' is a rigid type variable bound by the type signature for `fz' at EvalTaglessF.hs:263:17 `a' is a rigid type variable bound by the type signature for `lam' at EvalTaglessF.hs:248:16 Expected type: Z a1 String Inferred type: Z a String In the second argument of `(.)', namely `unZ' In the second argument of `(.)', namely `f . unZ' Failed, modules loaded: none. I hope this gives you a hint, if any. I am not exactly sure about how to solve this but I might try using scoped type variables extension somehow if I were in your shoe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] here is how I made it type check
I don't know if this is what you want but I was at least able to make it
to type check basically changing (fz . return) into simply return. I
think the error message about the occurs check was because of the fz
function is used wrong (or you didn't give it a correct type).
{-# LANGUAGE NoMonomorphismRestriction,TypeSynonymInstances,FlexibleInstances,MultiParamTypeClasses,ScopedTypeVariables #-}
-- Haskell' Committee seems to have agreed to remove the restriction
-- Tagless Typed lambda-calculus with integers and the conditional
-- in the higher-order abstract syntax.
-- Haskell itself ensures the object terms are well-typed.
-- Here we use the tagless final approach.
{-
module EvalTaglessF where
class Symantics repr where
l:: (repr t1 - repr t2) - repr (t1-t2)
a:: repr (t1-t2) - repr t1 - repr t2
i:: Int - repr Int
(+:) :: repr Int - repr Int - repr Int -- addition
ifz :: repr Int - repr t - repr t - repr t -- if zero
fix :: repr ((a-b) - (a-b)) - repr (a-b)
-- Let :: repr t1 - (repr t1 - repr t) - repr t
-- compared to EvalTaglessI, everything is in lower-case now
-- Since we rely on the metalanguage for typechecking and hence
-- type generalization, we have to use `let' of the metalanguage.
infixl 9 `a`
-- It is quite challenging to show terms. Yet, in contrast to the GADT-based
-- approach (EvalTaglessI.hs), we are able to do that, without
-- extending our language with auxiliary syntactic forms.
-- Incidentally, showing of terms is just another way of _evaluating_
-- them, to strings.
type VarCount = Int -- to build the names of variables
newtype S t = S (VarCount - (String,VarCount))
evals (S t) = t
instance Symantics S where
l f = S $ \c0 -
let vname = v ++ show c0
c1 = succ c0
(s,c2) = evals (f (S $ \c - (vname,c))) c1
in ((\\ ++ vname ++ - ++ s ++ ),c2)
a e1 e2 = S $ \c0 -
let (s1,c1) = evals e1 c0
(s2,c2) = evals e2 c1
in (( ++ s1 ++ ++ s2 ++ ),c2)
i n = S $ \c - (show n,c)
e1 +:e2 = S $ \c0 -
let (s1,c1) = evals e1 c0
(s2,c2) = evals e2 c1
in (( ++ s1 ++ + ++ s2 ++ ),c2)
ifz e1 e2 e3 = S $ \c0 -
let (s1,c1) = evals e1 c0
(s2,c2) = evals e2 c1
(s3,c3) = evals e3 c2
in ((ifz ++ s1 ++ ++ s2 ++ ++ s3 ++),c3)
fix e = S $ \c0 -
let (s1,c1) = evals e c0
in ((fix ++ s1 ++ ),c1)
tshow t = fst $ evals t 0
-- We no longer need variables or the environment and we do
-- normalization by evaluation.
-- Denotational semantics. Why?
newtype D t = D t -- This is not a tag. Why?
evald:: D t - t
evald (D t) = t
instance Symantics D where
l f = D $ \x - evald (f (D x))
a e1 e2 = D $ (evald e1) (evald e2)
i n = D $ n
e1 +: e2 = D $ evald e1 + evald e2
ifz e1 e2 e3 = D $ if evald e1 == 0 then evald e2 else evald e3
fix e= D $ hfix (evald e) where hfix f = f (hfix f)
{-
We can also give operational semantics, by implementing the function of the
following signature:
evalo :: (forall repr. Symantics repr = repr t) -
(forall repr. Symantics repr = repr t)
The signature has rank-2 type and hence this file requires a PRAGMA
declaration {-# LANGUAGE Rank2Types #-}
The implementation of evalo is exactly the partial evaluator of the
tagless final paper. Please see the paper for details.
-}
-- Tests
-- Truly the tests differ from those in EvalTaglessI.hs only in the case
-- of `syntax`: (i 1) vs (I 1), etc.
test0d = evald $ l(\vx - vx +: (i 2)) `a` (i 1) -- 3
term1 = l (\vx - ifz vx (i 1) (vx +: (i 2)))
test11d = evald $ term1
test11s = tshow $ term1 -- (\\v0- (ifz v0 1 (v0 + 2)))
test12d = evald (term1 `a` (i 2)) -- 4, as Haskell Int
-- test14 = evald (term1 `a` vx) -- Type error! Not in scope: `vx'
term2 = l (\vx - l (\vy - vx +: vy))
-- *EvalTaglessF :t term2
-- term2 :: (Symantics repr) = repr (Int - Int - Int)
test21 = evald term2
test23d = evald (term2 `a` (i 1) `a` (i 2)) -- 3
termid = l(\vx - vx)
testid = evald termid -- testid :: t1 - t1
term2a = l (\vx - l(\vy - vx `a` vy))
{- The meta-language figured the (polymorphic) type now
*EvalTaglessF :t term2a
term2a :: (Symantics repr) = repr ((t1 - t2) - t1 - t2)
-}
-- No longer hidden problems
-- term3 = l (\vx - ifz vx (i 1) vy) -- Not in scope: `vy'
-- The following is a type error, we can't even enter the term
-- term4 = l (\vx - ifz vx (i 1) (vx `a` (i 1)))
{- Now we get good error messages!
Couldn't match expected type `t1 - Int'
against inferred type `Int'
Expected type: repr (t1 - Int)
Inferred type: repr Int
In the first argument of `a', namely `vx'
In the third argument of `ifz', namely `(vx `a` (i 1))'
-}
-- (x+1)*y = x*y + y
-- why is this less of a cheating? Try showing the term
-- Now,
[Haskell-cafe] Re: Flipping *-*-* kinds, or monadic finally-tagless madness
Edward Kmett 쓴 글: Actually the problem lies in your definition of fz, it has the wrong type to be used in lam. The Z you get out of fz as type Z b String, but you need it to have Z (a - b) String so that when you strip off the Z you have a Y String (a - b) matching the result type of lam. To get there replace your definition of fz with: fz :: Z a String - Z (a - b) String fz = Z . Y . unY . f . unZ I think this seems to be the Yeoh wanted. Mine was just blinded hack just to make it type check without looking at what program means. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Reflections on the ICFP 2009 programming contest
Similar to mine except that I implemented with all of the memory (data, instruction, input and output ports) with the Data.Map library. One thing to care about is the heap memory profiling. You'll need to make sure that Map.insert function do not pile up as thunk. This is a typical memory leak profiling with most purely functional lazy data structures. I only tried the first problem, and it was good enough performance. But I don't have an idea how may timesteps it takes for the Operations Clear Sky. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Reflections on the ICFP 2009 programming contest
John Meacham 쓴 글: I implemented the VM in C, it was pretty obviously geared towards such an implementation and it took all of an hour. Then I interfaced with it via the FFI. Why use just one language when you can use two? :) You could also have used Data.Binary. That's what I did. I wasn't able to make any time on sunday though so didn't end up submitting a final entry which is too bad. this was an interesting one. John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Wondering about c type in haskell.
Magicloud Magiclouds 쓴 글: Hi, There are times, when we need to make some system calls, or call C library. So we have to deal with C data types. For example, CPid, which is an integer, actually. So we can do fromIntegral pid. Then why do not we define type CPid = Integer, and convert Haskell Integer with C Int internally. So the user does not have to care about the type convert (everywhere, which is ugly). And, specially, when doing something like serialisation, for Haskell Integer, the user does not have to do things with precision. But for CPid, without the fromIntegral, we have to specify its precision, well, on different machine/OS, the precision may not be the same. Integer is not a fixed length chunk of bits. It can be arbitrarily large as long as there is memory left in the system. It's theoretically more clean being close to a mathematical definition of integers, but internally a complicated beast. So defining CPid as Integer is just not sane. In addition, we cannot use Int either. Int is not a 32 bit or 64 bit word. The Haskell 98 standard does not require that, and in most implementations it is 2^31 singed bits using one bit as a mark to distinguish pointers from values for garbage collection purposes. (OCaml int types are like that too.) I hope this gives enough explanation. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Wondering about c type in haskell.
Ahn, Ki Yung 쓴 글: Magicloud Magiclouds 쓴 글: Hi, There are times, when we need to make some system calls, or call C library. So we have to deal with C data types. For example, CPid, which is an integer, actually. So we can do fromIntegral pid. Then why do not we define type CPid = Integer, and convert Haskell Integer with C Int internally. So the user does not have to care about the type convert (everywhere, which is ugly). And, specially, when doing something like serialisation, for Haskell Integer, the user does not have to do things with precision. But for CPid, without the fromIntegral, we have to specify its precision, well, on different machine/OS, the precision may not be the same. Integer is not a fixed length chunk of bits. It can be arbitrarily large as long as there is memory left in the system. It's theoretically more clean being close to a mathematical definition of integers, but internally a complicated beast. So defining CPid as Integer is just not sane. In addition, we cannot use Int either. Int is not a 32 bit or 64 bit word. The Haskell 98 standard does not require that, and in most implementations it is 2^31 singed bits using one bit as a mark to distinguish pointers from values for garbage collection purposes. (OCaml int types are like that too.) I hope this gives enough explanation. I wrote this and thought that you might already know this. For convenience of serialization, wouldn't defining Data.Binary instances for C types be enough in the library level? -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: memscript-0.0.0.2 (Command line utility for memorizing scriptures or any other text)
memscript: Command line utility for memorizing scriptures or any other text http://hackage.haskell.org/cgi-bin/hackage-scripts/package/memscript memscript filename Run memscript with a UTF-8 (or ASCII since ASCII is a subset of UTF8) plain text file. Try to exactly guess the text line by line. If your guess is wrong it will show you a diff like output comparing your guess and the original verse. This will repeat until you get all the verses right. For the test data I included four beloved Psalms (1,23,121,127) from the Old Testament, each in Revised Korean Version (RKV) and New International Version (NIV), which I happened to have had to memorize. You can use it for any other text you'd want to memorize, such as your favorite poems, quotes, or whatsoever. No craft or ticks, really simple and straightforward utility but serves well for the purpose. I used readline because that was the only sane way I know of handling multibyte inputs. an example usage kya...@kyagrd:~/cscs/memscript$ memscript 001en.txt % Blessed is the man who does not walk in the counsel of the wicked or stand in the way of sinners or sit in the seat of mockers. % But his delight is in the law of the LORD, and on his law he meditates night and day. === But his delight is in the law of the LORD, and on his law he meditates day and night. --- But his delight is in the law of the LORD, and on his law he meditates night and day. === % But his delight is in the law of the LORD, and on his law he meditates day and night. % He is like a tree planted by streams of water, which yields its fruit in season and whose leaf does not wither. Whatever he does prospers. % Not so the wicked! They are like chaff that the wind blows away. % The wicked will not stand in the judgment, nor sinners in the assembly of the righteous. === Therefore the wicked will not stand in the judgment, nor sinners in the assembly of the righteous. --- The wicked will not stand in the judgment, nor sinners in the assembly of the righteous. === % Therefore the wicked will not stand in the judgment, nor sinners in the assembly of the righteous. % For the LORD watches over the way of the righteous, but the way of the wicked will perish. kya...@kyagrd:~/cscs/memscript$ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Scary type inference for monadic function definitions
Scary type inference for monadic function definitions (or, why you'd want to annotate types for monadic function definitions) This is a real example that I've experienced. I defined the following function. checkOneVerseByLineWith readLine v = do mg - readLine case mg of Just g - return Just (v==g) Nothing - return Nothing My intention was to use it something like this: checkOneVerseByLineWith (readline % ) where readline is the library function from System.Console.Readline. As you can see, there is an obvious mistake which I forgot to group (Just (v==g)) in parenthesis. However, GHC or any other Haskell 98 compliant implementation will infer a type for you and this will type check! Try it yourself if in doubt. Of course, checkOneVerseByLineWith (readline % ) won't type check because checkOneVerseByLineWith has strange type. The reason why the above definition type checks is because ((-) r) is an instance of Monad. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Scary type inference for monadic function definitions
Ahn, Ki Yung 쓴 글: Scary type inference for monadic function definitions (or, why you'd want to annotate types for monadic function definitions) This is a real example that I've experienced. I defined the following function. checkOneVerseByLineWith readLine v = do mg - readLine case mg of Just g - return Just (v==g) Nothing - return Nothing My intention was to use it something like this: checkOneVerseByLineWith (readline % ) where readline is the library function from System.Console.Readline. As you can see, there is an obvious mistake which I forgot to group (Just (v==g)) in parenthesis. However, GHC or any other Haskell 98 compliant implementation will infer a type for you and this will type check! Try it yourself if in doubt. Of course, checkOneVerseByLineWith (readline % ) won't type check because checkOneVerseByLineWith has strange type. The reason why the above definition type checks is because ((-) r) is an instance of Monad. Oh, I happened to be importing Control.Monad.Trans somehow, it just doesn't work with Prelude import itself. And, there were already some discussions on this last year: [Haskell-cafe] The danger of Monad ((-) r) http://www.mail-archive.com/haskell-cafe@haskell.org/msg23680.html Tomasz Zielonka Tue, 15 May 2007 03:05:30 -0700 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Purely logical programming language
Henning Thielemann wrote: On Tue, 26 May 2009, Jan Christiansen wrote: Hi, On 26.05.2009, at 21:24, Lauri Alanko wrote: Mercury also has type classes and other Haskellisms, so if you're interested in doing Prolog the Haskell way, you should definitely have a look at it. I have to admit that I am not very familiar with Mercury. But if you are looking for doing Prolog the Haskell way advertiseyou can also have a look at Curry/advertise. Curry is a lazy functional logic programming language that has a Haskell like syntax (http://www.curry-language.org/). You forgot to mention, that you will give a talk about Curry soon, where Matthias might want to attend: http://iba-cg.de/hal4.html :-) By the way, did Curry solved the problem of how to deal with IO and backtracking issues? (where and where not should IO happen kind of a thing) I haven't used Curry that much but I remember that there was an issue of IO and non-determinism. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Visualizing Typed Functions
Duane Johnson wrote: With these functions visualized, one could make a kind of drag and drop interface for Haskell programming, although that isn't really my intention. I admit this is a little convoluted even for the purpose of visualization, but at least it's a starting place. Does anyone know of another system or better representation? You must to take a look at this: Tangible Functional Programming http://www.youtube.com/watch?v=faJ8N0giqzw And, a little bit off topic but cool stuff: Vacuum: visualize Haskell data structures live http://www.youtube.com/watch?v=X4-212uMgy8 @ It seems that we are getting pretty close to the point that youtube is getting to be a better reference than a paper, at least for practitioners. A lot of talks are on youtube :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ANNOUNCE: The Haskell Platform
Thanks for this great effort! Are we going to have a meta-package on hackage as well? (which makes it able to build it through cabal-install) -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Question concerning Haskell Foundation
Don Stewart wrote: vigalchin: Hello, With Haskell Foundation, 1) Can we still publish packages on Hackage? 2) Is Hackage going away? ??? -- Don Don, I think he's referring to your recent announcement about the Haskell platform. And, at that thread you also mentioned that Haskell platform is also going to be provided as a meta-package on Hackage. So, the answers to 1) Yes, 2) No. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] HPong-0.1.2 fails to compile in Debian ghc 6.10.1
I don't know the exact reason but this should not fail since I have Debian packaged ghc 6.10.1 and OpenGL-2.2.1.1 on my system. I think this is because the filename of the OpenGL shared library is /usr/lib/libGL.so.1 rather than libGL.so. This is why we have two binary distributions for Linux because editline library has the same naming issues in Debian. So, this may be Debian packaging problem of OpenGL bindings. But the interesting thing is that I was able to work around this in Debian, by temporarily making a symbolic link libGL.so pointing to libGL.so.1 and it hpong built successfully. Once it builds, hpong still runs even if I delete the symbolic link libGL.so. So, there is also a possibility that what may be wrong is with the build system (cabal or ghc). Thanks in advance for related library packaging mangers and developers, and here are the details of failure: kya...@kyagrd:~/cscs/stlcwpat$ uname -a Linux kyagrd 2.6.26-2-686 #1 SMP Thu Mar 26 01:08:11 UTC 2009 i686 GNU/Linux kya...@kyagrd:~/cscs/stlcwpat$ ghc --version The Glorious Glasgow Haskell Compilation System, version 6.10.1 kya...@kyagrd:~/cscs/stlcwpat$ which ghc /usr/bin/ghc kya...@kyagrd:~/cscs/stlcwpat$ cabal update Downloading the latest package list from hackage.haskell.org kya...@kyagrd:~/cscs/stlcwpat$ cabal install HPong Resolving dependencies... Configuring HPong-0.1.2... Preprocessing executables for HPong-0.1.2... Building HPong-0.1.2... [1 of 1] Compiling Main ( HPong.hs, dist/build/hpong/hpong-tmp/Main.o ) Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Loading package syb ... linking ... done. Loading package base-3.0.3.0 ... linking ... done. Loading package array-0.2.0.0 ... linking ... done. Loading package containers-0.2.0.0 ... linking ... done. Loading package transformers-0.1.4.0 ... linking ... done. Loading package data-accessor-0.2.0.2 ... linking ... done. Loading package packedstring-0.1.0.1 ... linking ... done. Loading package pretty-1.0.1.0 ... linking ... done. Loading package template-haskell ... linking ... done. Loading package utility-ht-0.0.4 ... linking ... done. Loading package data-accessor-template-0.2.1.1 ... linking ... done. Loading package OpenGL-2.2.1.1 ... command line: can't load .so/.DLL for: GL (libGL.so: cannot open shared object file: No such file or directory) cabal: Error: some packages failed to install: HPong-0.1.2 failed during the building phase. The exception was: exit: ExitFailure 1 kya...@kyagrd:~/cscs/stlcwpat$ ghc-pkg list /usr/lib/ghc-6.10.1/./package.conf: ALUT-2.1.0.0, Cabal-1.6.0.1, Diff-0.1.2, GLUT-2.1.1.2, HDBC-2.1.0, HDBC-postgresql-2.1.0.1, HGL-3.2.0.0, HUnit-1.2.0.3, OpenAL-1.3.1.1, OpenGL-2.2.1.1, QuickCheck-2.1.0.1, Stream-0.2.2, X11-1.4.5, X11-xft-0.3, array-0.2.0.0, arrows-0.4.1, base-3.0.3.0, base-4.0.0.0, binary-0.5, bytestring-0.9.1.4, cairo-0.10.0, cgi-3001.1.7.1, containers-0.2.0.0, convertible-1.0.2, directory-1.0.0.2, editline-0.2.1.0, fgl-5.4.2.2, filepath-1.1.0.1, (ghc-6.10.1), ghc-prim-0.1.0.0, gio-0.10.0, glade-0.10.0, glib-0.10.0, gstreamer-0.10.0, gtk-0.10.0, gtkglext-0.10.0, gtksourceview2-0.10.0, haskell-src-1.0.1.3, haskell98-1.0.1.0, hpc-0.5.0.2, hslogger-1.0.8, html-1.0.1.2, integer-0.1.0.0, irc-0.4.3, mtl-1.1.0.2, network-2.2.0.1, old-locale-1.0.0.1, old-time-1.0.0.1, packedstring-0.1.0.1, parallel-1.1.0.0, parsec-3.0.0, pretty-1.0.1.0, process-1.0.1.0, random-1.0.0.1, regex-base-0.93.1, regex-compat-0.92, regex-posix-0.93.1, rts-1.0, soegtk-0.10.0, stm-2.1.1.2, svgcairo-0.10.0, syb-0.1.0.0, syb-with-class-0.5.1, tagsoup-0.6, template-haskell-2.3.0.0, terminfo-0.3.0.1, time-1.1.2.3, unix-2.3.1.0, utf8-string-0.3.4, xhtml-3000.2.0.1, xmonad-0.8.1, xmonad-contrib-0.8.1, zlib-0.5.0.0 /home/kyagrd/.ghc/i386-linux-6.10.1/package.conf: Cabal-1.6.0.1, Cabal-1.6.0.2, GLFW-0.3, HGL-3.2.0.0, HTTP-3001.1.3, HTTP-4000.0.4, HTTP-4000.0.5, InfixApplicative-1.0.1, QuickCheck-1.2.0.0, QuickCheck-2.1.0.1, Stream-0.3.1, arrows-0.4.1, binary-0.5.0.1, cgi-3001.1.7.1, data-accessor-0.2.0.2, data-accessor-monads-fd-0.2, data-accessor-template-0.2.1.1, derive-0.1.4, extensible-exceptions-0.1.1.0, filepath-1.1.0.2, fingertree-0.0, ghc-paths-0.1.0.5, haddock-2.4.1, haskell98-1.0.1.0, irc-0.4.3, lazysmallcheck-0.3, (monads-fd-0.0.0.1), network-2.2.0.1, network-2.2.1, old-time-1.0.0.2, parsec-2.1.0.1, pointedlist-0.3.1, process-1.0.1.1, pureMD5-0.2.4, random-1.0.0.1, regex-tdfa-1.0.0, rosezipper-0.1, sparsebit-0.5, split-0.1.1, terminfo-0.3.0.2, transformers-0.1.4.0, uniplate-1.2.0.3, unix-compat-0.1.2.1, utility-ht-0.0.4, vty-3.1.8.4, yi-0.6.0, zlib-0.4.0.4, zlib-0.5.0.0 kya...@kyagrd:~/cscs/stlcwpat$ ls /usr/lib/*GL* /usr/lib/libGL.so.1@ /usr/lib/libGLU.so.1.3.070300 /usr/lib/libGL.so.180.44
[Haskell-cafe] ANN: smartword 0.0.0.5 Web based flash card for Word Smart I and II vocabularies
Name:smartword Synopsis:Web based flash card for Word Smart I and II vocabularies Version: 0.0.0.5 Homepage:http://kyagrd.dyndns.org/~kyagrd/project/smartword/ Category:Web,Education License: BSD3 License-file:LICENSE Author: Ahn, Ki Yung Maintainer: Ahn, Ki Yung k...@pdx.edu === Web based online study tool for all vocabularies in Word Smart I and II, a poular book series for studying GRE vocabularies. I typed the vocabulary data and wrote the program in 2004, because I got too boring just going over the strange English words. If you don't read Korean, you can just ignore the Korean translation. Source code is outdated, so never even think of using it as a web programming reference. However, it will still be helpful as a neat web application when one tries to squeeze GRE vocabularies into the volatile memory of human brain. Installation: You can either compile CGI binaries with GHC or use Hugs to run lhs as a CGI script. Copy all .cgi files and data directories (book1, book1.ans, book2, book2.ans) into your webserver CGI directory (usually cgi-bin). Usage: If you get it wright the flash card goes away, but if you didn't get it the flash card goes to the bottom of the deck again. So, it won't end until you get all of them right. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: sparsebit 0.5 - Sparse Bitmaps for Pattern Match Coverage
sparsebit - Sparse Bitmaps for Pattern Match Coverage http://hackage.haskell.org/cgi-bin/hackage-scripts/package/sparsebit This library packages the functional peal paper 'Sparse Bitmaps for Pattern Match Coverage' submitted to ICFP 2009 by Ki Yung Ahn and Tim Sheard. You can look up the tutorial-like paper and the talk slides, which are availabel at: http://kyagrd.dyndns.org/wiki/SparseBitmapsForPatternMatchCoverage Abstract: Pattern matching coverage over Algebraic Data Types(ADTs) has most often been studied in the context of pattern compilation algorithms. However, it is worth considering the pattern matching coverage problem in isolation, since general solutions will be independent of the specifics of any implementation or language. We define an intuitive and mathematically well-established bit masking semantics for pattern match coverage. We design and implement a sparse bitmap data structure, which realizes this semantics in a compact and flexible manner. This bitmap data structure supports computing coverage solutions of large programs incrementally from coverage solutions of sub-programs. It can also be used as a common data representation for pattern coverage shared between different tools (e.g., compilers, linting tools, software analysis tools) that need pattern match coverage information. Additional source files Type.hs and TestType.hs packaged with this library provides the examples and QuickCheck extracted from the paper to demonstrate how to use this library. Some additional notes: Personally, I am very happy to upload my first project on Hackage. If you are looking for simple and elegant way of describing pattern match coverage or testing exhaustiveness of pattern matching, we hope this may give you a better insight. This is a reference implementation, but I think it is still usable to some extent. One might want to define monadic version of the library functions and operators since the type representation in the program analysis tools might be monadic for implementation reasons (easy to generate fresh type variables) and performance reasons (to exploit sharing while unification of type variables). And in such cases, more optimized implementation of tensor product may be possible as well. And there are some other issues discussed in the paper as well. I was not able to make the haddock documentation appear in Hackage, although I have no problem generating documentation using cabal haddock locally. It would be nice if there is a way to see some diagnose of warning or error messages why haddock failed on Hackage. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal-install 0.6.2 does not bootstrap with ghc-6.10.1 debian distribution
Duncan Coutts 쓴 글: On Sat, 2009-03-07 at 17:51 -0800, Ahn, Ki Yung wrote: Dear Haskellers and especially who are working on cabal-install and debian packaging, I sometimes clean up .ghc and .cabal in my home directory to start from scratch because of dependency loopholes (cabal-install does not have remove option yet, so it's hard to fix when such loophole happens). Today, I had some time in the airport and decided to start from scratch again because of the dependency loophole with process 1.0.1.1 and haddock. I downloaded the most recent version of cabal-install the version 0.6.2, and found out that the ./bootstrap.sh does not work. If you could provide any details on how it does not work that would be much appreciated. Eg a log of the output from running the bootstrap. Duncan I am using Debian unstable. The version of GHC debian package is 6.10.1+dfsg1-13, and installed Haskell libraries (debian packages) are: kya...@kyavaio:~$ ghc-pkg list /usr/lib/ghc-6.10.1/./package.conf: Cabal-1.6.0.1, Diff-0.1.2, HGL-3.2.0.0, HUnit-1.2.0.3, QuickCheck-2.1.0.1, Stream-0.2.2, X11-1.4.5, array-0.2.0.0, arrows-0.4.1, base-3.0.3.0, base-4.0.0.0, binary-0.5, bytestring-0.9.1.4, cairo-0.10.0, cgi-3001.1.7.1, containers-0.2.0.0, directory-1.0.0.2, editline-0.2.1.0, fgl-5.4.2.2, filepath-1.1.0.1, gconf-0.10.0, (ghc-6.10.1), ghc-prim-0.1.0.0, gio-0.10.0, glade-0.10.0, glib-0.10.0, gnomevfs-0.10.0, gstreamer-0.10.0, gtk-0.10.0, gtkglext-0.10.0, gtksourceview2-0.10.0, haskell98-1.0.1.0, hpc-0.5.0.2, html-1.0.1.2, integer-0.1.0.0, irc-0.4.3, mtl-1.1.0.2, network-2.2.0.1, old-locale-1.0.0.1, old-time-1.0.0.1, packedstring-0.1.0.1, parallel-1.1.0.0, parsec-3.0.0, pretty-1.0.1.0, process-1.0.1.0, random-1.0.0.1, rts-1.0, stm-2.1.1.2, svgcairo-0.10.0, syb-0.1.0.0, syb-with-class-0.5.1, tagsoup-0.6, template-haskell-2.3.0.0, time-1.1.2.3, unix-2.3.1.0, utf8-string-0.3.4, xhtml-3000.2.0.1 Bootstrap fails like this: kya...@kyavaio:~/tmp/cabal-install-0.6.2$ sh bootstrap.sh Checking installed packages for ghc-6.10.1... The Haskell package 'parsec' is required but it is not installed. If you are using a ghc package provided by your operating system then install the corresponding packages for 'parsec' and 'network'. If you built ghc from source with only the core libraries then you should install these extra packages. You can get them from hackage. Error during cabal-install bootstrap: The Haskell package 'parsec' is required but it is not installed. P.S. Note, parsec and network are installed in the system using debian distribution packages. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] cabal-install 0.6.2 does not bootstrap with ghc-6.10.1 debian distribution
Dear Haskellers and especially who are working on cabal-install and debian packaging, I sometimes clean up .ghc and .cabal in my home directory to start from scratch because of dependency loopholes (cabal-install does not have remove option yet, so it's hard to fix when such loophole happens). Today, I had some time in the airport and decided to start from scratch again because of the dependency loophole with process 1.0.1.1 and haddock. I downloaded the most recent version of cabal-install the version 0.6.2, and found out that the ./bootstrap.sh does not work. So, I had to bootstrap from version 0.6.2 and do cabal update and cabal upgrade cabal-install to upgrade to 0.6.2. I am not sure whether this is a cabal-install problem or debian dstribution ghc-6.10.1 packaging probelm, since I have not tried to test this with any other ghc-6.10.1 distribution. If anyone who are not using debian distribution ghc-6.10.1 (e.g., general linux binary ghc-6.10.1 or source compiled one) can try bootstrapping cabal-install 0.6.2 from scratch also finds the same problem, I think someone should make a ticket for cabal-install. Thanks, Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: cabal-install 0.6.2 does not bootstrap with ghc-6.10.1 debian distribution
Ahn, Ki Yung 쓴 글: Dear Haskellers and especially who are working on cabal-install and debian packaging, I sometimes clean up .ghc and .cabal in my home directory to start from scratch because of dependency loopholes (cabal-install does not have remove option yet, so it's hard to fix when such loophole happens). Today, I had some time in the airport and decided to start from scratch again because of the dependency loophole with process 1.0.1.1 and haddock. I downloaded the most recent version of cabal-install the version 0.6.2, and found out that the ./bootstrap.sh does not work. So, I had to bootstrap from version 0.6.2 and do cabal update and cabal upgrade cabal-install to upgrade to 0.6.2. Sorry for my typo. What I meant was: I was able to bootstrapped from version 0.6.0 and then upgrade to 0.6.2. I am not sure whether this is a cabal-install problem or debian dstribution ghc-6.10.1 packaging probelm, since I have not tried to test this with any other ghc-6.10.1 distribution. If anyone who are not using debian distribution ghc-6.10.1 (e.g., general linux binary ghc-6.10.1 or source compiled one) can try bootstrapping cabal-install 0.6.2 from scratch also finds the same problem, I think someone should make a ticket for cabal-install. Thanks, Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: speed: ghc vs gcc
Thomas Davie wrote: You need look no further than the debian language shootout that things really aren't as bad as you're making out – Haskell comes in in general less than 3x slower than gcc compiled C. Of note, of all the managed languages, this is about the fastest – none of the other languages that offer safety and garbage collection etc get as close as Haskell does. Bob OCaml and Clean seems to be pretty fast too. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Type families not as useful over functions
My thoughts on type families: 1) Type families are often too open. I causes rigid variable type error messages because when I start writing open type functions, I often realize that what I really intend is not truly open type functions. It happens a lot that I had some assumptions on the arguments or the range of the type function. Then, we need help of type classes to constrain the result of open type functions. For example, try to define HList library using type families instead of type classes with functional dependencies. One will soon need some class constraints. Sometimes, we can use associated type families, but many times it may become tedious when there are multiple arguments and result have certain constraints so that we might end up associating/splitting them over multiple type classes. In such cases, it may be more simple working with functional dependencies alone, rather than using both type classes and type families. I wish we had closed kinds so that we can define closed type functions as well as open type functions. 2) Type families are not good when we need to match types back and forth (e.g. bijective functions), or even multiple ways. We need the help of functional dependencies for these relational definitions. I know that several people are working on the unified implementation for both type families and functional dependencies. Once GHC have common background implementation, type families will truly be syntactic sugar of type classes with functional dependencies, as Mark Jones advocates, or maybe the other way around too. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: 1000 libraries
Don Stewart wrote: We've done it! Thanks for the good news. Maybe it's already getting more important organizing existing uesful set of libraries as mata-packages. Are there updates on haskell-platform? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] tensor product of dynamic-sized bits
For some reasons, I am trying to write a small Haskell code for tensor products (See http://en.wikipedia.org/wiki/Tensor_product) of bits, which can expand or shrink their size and dimension as needed. Has anyone already done similar or more general work before? If so, I'd be happy use/consult that and cite the work. Otherwise, I should think about cleaning up and packaging this as a library. My code is like this right now: data Bits = O -- all 1 bits of any size and dimension | I -- all 0 bits of any size and dimension | Bs [Bits] -- row of bits possibly nested | Rep Bits -- repeating of bits (e.g. O = Rep O = Bs [O,O]) deriving (Eq,Show) bitwise-and O . _ = O _ . O = O (Rep O) . _ = O _ . (Rep O) = O (Bs (O:xs)) . _ | all (O==) xs = O _ . (Bs (O:xs)) | all (O==) xs = O I . y = y x . I = x (Rep I) . y = y x . (Rep I) = x (Bs (I:xs)) . y | all (I==) xs = y x . (Bs (I:ys)) | all (I==) ys = x (Bs xs) . (Bs ys) = reduce $ Bs (zipWith (.) xs ys) (Rep x) . (Bs ys) = reduce $ Bs (xs .. ys) where xs=repeat x (Bs xs) . (Rep y) = reduce $ Bs (xs .. ys) where ys=repeat y (Rep x) . (Rep y) = reduce $ Rep (x . y) (..) = zipWith (.) bitwise-or O .| y = y x .| O = x (Rep O) .| y = y x .| (Rep O) = x (Bs (O:xs)) .| y | all (O==) xs = y x .| (Bs (O:ys)) | all (O==) ys = x I .| _ = I _ .| I = I (Rep I) .| _ = I _ .| (Rep I) = I (Bs (I:xs)) .| _ | all (I==) xs = I _ .| (Bs (I:ys)) | all (I==) ys = I (Bs xs) .| (Bs ys) = reduce $ Bs (xs .|. ys) (Rep x) .| (Bs ys) = reduce $ Bs (xs .|. ys) where xs=repeat x (Bs xs) .| (Rep y) = reduce $ Bs (xs .|. ys) where ys=repeat y (Rep x) .| (Rep y) = reduce $ Rep (x .| y) (.|.) = zipWith (.|) tensor product O .* _ = O _ .* O = O (Rep O) .* _ = O _ .* (Rep O) = O (Bs (O:xs)) .* _ | all (O==) xs = O _ .* (Bs (O:ys)) | all (O==) ys = O I .* I = I I .* (Rep y) = I .* y (Rep I) .* y = I .* y (Bs (I:xs)) .* y | all (I==) xs = I .* y I .* y = reduce $ Rep y x .* (Rep I) = x .* I x .* (Bs (I:xs)) | all (I==) xs = x .* I x .* I = x (Bs xs) .* (Bs ys) = reduce $ Bs (xs .*. ys) (Bs xs) .* (Rep y) = reduce $ Bs (map (reduce . Rep) $ xs .*. [y]) (Rep x) .* y = reduce $ Rep (x .* y) [] .*. _ = [] (x:xs) .*. ys = (reduce $ Bs [x .* y | y-ys]) : (xs .*. ys) reducing from Bs [O,O,..] to O and from Bs [I,I,..] to I reduce (Bs (x:xs)) | all (x==) xs = x reduce (Rep x@(Rep _)) = x reduce x = x Some example run on Hugs: Main Bs [I,O] Bs [I,O] Main Bs [I,O] .| Bs [O,Bs [I,I,I,I] .* Bs [I,O,O,O,O]] Bs [I,Rep (Bs [I,O,O,O,O])] Main Bs [I,O] .| Bs [O, Bs [I,I,I,I] .* Bs [I,O,O,O,O]] .| Bs [O, Bs [I,O,O,O] .* Bs [I,I,I,I,I]] Bs [I,Bs [I,Bs [I,O,O,O,O],Bs [I,O,O,O,O],Bs [I,O,O,O,O]]] Main Bs [I,O] .| Bs [O, Bs [I,I,I,I] .* Bs [I,O,O,O,O]] .| Bs [O, Bs [I,O,O,O] .* Bs [I,I,I,I,I]] .| Bs [O, Bs [O,I,I,O] .* Bs [O,I,I,O,O]] Bs [I,Bs [I,Bs [I,I,I,O,O],Bs [I,I,I,O,O],Bs [I,O,O,O,O]]] Main Bs [I,O] .| Bs [O, Bs [I,I,I,I] .* Bs [I,O,O,O,O]] .| Bs [O, Bs [I,O,O,O] .* Bs [I,I,I,I,I]] .| Bs [O, Bs [O,I,I,O] .* Bs [O,I,I,O,O]] .| Bs [O, Bs [O,I,I,I] .* Bs [O,O,O,I,I]] Bs [I,Bs [I,I,I,Bs [I,O,O,I,I]]] Main Bs [I,O] .| Bs [O, Bs [I,I,I,I] .* Bs [I,O,O,O,O]] .| Bs [O, Bs [I,O,O,O] .* Bs [I,I,I,I,I]] .| Bs [O, Bs [O,I,I,O] .* Bs [O,I,I,O,O]] .| Bs [O, Bs [O,I,I,I] .* Bs [O,O,O,I,I]] .| Bs [O, Bs [O,O,I,I] .* Bs [O,I,I,O,O]] I ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: tensor product of dynamic-sized bits
Ahn, Ki Yung 쓴 글: reduce (Bs (x:xs)) | all (x==) xs = x reduce (Rep x@(Rep _)) = x reduce x = x I already found a bug. The second equation of reduce reduce (Rep x@(Rep _)) = x is wrong because it flattens two dimensions into one. The reduce function should be: reduce x = x reduce (Bs (x:xs)) | all (x==) xs = reduce x reduce (Bs xs) = Bs (map reduce xs) reduce (Rep O) = O reduce (Rep I) = I reduce (Rep x) = Rep (reduce x) reduce x = x This is why I am looking for existing work, because I am not yet very sure about my code I'm using. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell good for parallelism/concurrency on manycore?
Dear Haskellers, I just got an inquiry from a research department head of a Korean company seriously considering to adopt functional languages because they heard that functional languages can do good at parallel programming on manycore platforms. They want to know what technologies out there implemented in functional languages, such as Erlang or Haskell, that can help them write more maintainable programs that are better at utilizing parallelism and avoiding bugs related to synchronization. They are also very interested in Cilk, as well as Haskell or Erlang. My first thought is that maybe Cilk would work better for them just because it would not be easy to recruit Erlang or Haskell programmers experienced in network, security, or concurrent/parallel programming. I myself can answer basic inquiries such as what libraries to look for to implenent such and so, but not able to give advice on large scale projects such as unified security solution package. So, it wouldn't be practical form them to launch a project without inviting an Erlang or Haskell expert in their domain as a project manager from overseas, which I don't think they are very willing to do. Are there Haskell consultants or Haskell experts on this subject, who believes that Haskell based approach might work better for them, or Haskell can be useful along with other approaches (e.g. DSL, prototyping, formal modeling of policies)? If so, I would like to recommend them trying contact you, and try my best to help communicating with them, if needed. They know English, of course, but may not be familiar with functional programming orlanguage-oriented programming jargons such as DSLs, oops, I mean language middleware :-) For your information: The company is a network security company whose main products are VPN and firewall appliances and their management software. Their research department is in search of better technologies to implement their future UTM (unified threat management) solutions utilizing the manycore platforms. In Korea, there are some research groups and few companies using OCaml, but almost no Erlang or Haskell communities. This company is preferring local researchers or consultants for advice or consulting, but there's no local group using Haskell seriously, as far as I know, even in research yet. That's why this person contacted me, just because I wrote a small tutorial on Haskell Server Programming while ago. P.S. If you happen to be a local Korean expert on this matter, sorry for my ignorance, and I'd be happy to forward their inquiry to you! -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Graham Hutton's calculator example for win32
In Graham Hutton's Programming in Haskell there is an interactive calculator example using ANSI code to implement the UI on the terminal. This example doesn't work on MS Windows XP or other MS OSes based on NT kernel, since their command line does not support ANSI very well. But, thanks to ansi-terminal on Hackage, I was able to extract minimal code from the package to make a win32 version of the calculator example in Hutton's book. calculatorWin32.lhs and Win32ANSI.hs is an implementation for win32. I extracted the win32 console API bindings for setting cursor positions from ansi-terminal project and put them in Win32ANSI.hs. I had to put this in a separate file because I had an issue with ghci. To run this, I had to compile the console API bindings with ghc first and then run ghci as follows C:\ ghc -c Win32ANSI.hs C:\ ghci calculatorWin32.lhs Without compiling the object code, ghci cannot find the proper link for win32 console API FFI bindings. C:\ ghci calculatorWin32.lhs GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. [1 of 3] Compiling Parsing ( Parsing.lhs, interpreted ) [2 of 3] Compiling Win32ANSI( Win32ANSI.hs, interpreted ) During interactive linking, GHCi couldn't find the following symbol: getconsolescreenbufferi...@8 This may be due to you not asking GHCi to load extra object files, archives or DLLs needed by your current session. Restart GHCi, specifying the missing library using the -L/path/to/object/dir and -lmissinglibname flags, or simply by naming the relevant files on the GHCi command line. Alternatively, this link failure might indicate a bug in GHCi. If you suspect the latter, please send a bug report to: glasgow-haskell-b...@haskell.org Is this a bug or a natural behavior of ghci? This is strange to me since ghci finds the proper link for the functions in the other C libraries such as getch in conio.h. In addition, I am attaching a patched calculator.lhs which works for Unix/Linux on both GHC 6.8.x and GHC 6.10.1. The one currently on the book homepage only works for GHC 6.8.x but not GHC 6.10.1. This is due to the bug fix of hSetBuffering in GHC 6.10.1. To run these calculator example you will also need Parsing.lhs from the book hompage.http://www.cs.nott.ac.uk/~gmh/Parsing.lhs -- Ahn, Ki Yung Calculator example from section 9.6 of Programming in Haskell, Graham Hutton, Cambridge University Press, 2007. Note: the definition for getCh in this example works with the Glasgow Haskell Compiler, but may not work with some Haskell systems, such as Hugs. Moreover, the use of control characters may not work on some systems, such as WinHugs. Note: This code works for both GHC versions 6.8.x and 6.10.1 on Unix/Linux. Previous code on the webpage only worked on GHC 6.8.x. -- Ahn, Ki Yung import Parsing import System.IO Parser for expressions -- expr :: Parser Int expr = do t - term do symbol + e - expr return (t + e) +++ do symbol - e - expr return (t - e) +++ return t term :: Parser Int term = do f - factor do symbol * t - term return (f * t) +++ do symbol / t - term return (f `div` t) +++ return f factor:: Parser Int factor= do symbol ( e - expr symbol ) return e +++ integer Derived primitives -- getCh :: IO Char getCh = do hSetEcho stdin False hSetBuffering stdin NoBuffering c - getChar hSetEcho stdin True hSetBuffering stdin LineBuffering return c beep :: IO () beep = putStr \BEL cls :: IO () cls = putStr \ESC[2J type Pos = (Int,Int) goto :: Pos - IO () goto (x,y)= putStr (\ESC[ ++ show
[Haskell-cafe] Re: ANN: Real World Haskell, now shipping
Andrew Coppin 쓴 글: Then again, one day I sat down and tried to draw a diagram of the essential concepts, techniques and syntax of Haskell and how they're related... The result looked like alphabet soup! It's not clear how you start to explain anything without immediately needing to explain 20 other things you just used to explain the first thing. (Somebody commented recursive tutorials for a recursive language. It was meant as an insult, but I actually kinda like it...) Given that that's the case, I'm not really sure that I could do any better than the Three Kings, so maybe I should just shuffle off and keep my comments to myself. :-/ If one needs introductory Haskell programming tutorial explaining about the language concepts from first principles, then one should read a textbook written for that purpose such as Programming in Haskell. Real World Haskell is a collection of practical tips and know-hows to get things done at work rather than a step-by-step Haskell tutorial. And I believe that many other O'Reilly books are like that. What I *haven't* done yet is read the chapters where they try to claim that database programming is possible in Haskell. I'll have to do that at some point. Maybe this is where they reveal the Secret Formula that makes this stuff actually work properly... but somehow I doubt it. What do you mean by that they are trying database programming is possible in Haskell? I've done very simple database programming in Haskell using HDBC, and it just works using the binary package from debian. If you need more complicated examples, you can take a look at the hpodder source code or any other applications that use database. They are all on Hackage. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Do I need an account to report build of Hacakge packages?
I am just curious about how cabal report works.
I recently figured out that there is a report command in cabal and it
reports the reports generated by --build-reports option when building a
package.
Is this because I don't have an account on Hackage yet, or because of
some other reasons?
And if I make an account, where how I put that information in cabal
config file?
I've looked into the cabal config file and tried to change this myself
before, but it wasn't very self explanatory to me. For instance, I
tried to make the build-reports on by default, deleting haskell comment
like double dashes -- and put True flag after the colon, but keep
getting parse error from cabal. I looked up the manual but it says that
the config file is self explanatory, which isn't to me at all. Are
there any documentations on this available anywhere?
=== error messages when I tried to report the build log ===
[EMAIL PROTECTED]:~$ cabal report
Sending:
POST http://hackage.haskell.org/buildreports HTTP/1.1
Content-Type: text/plain
Content-Length: 281
Accept: text/plain
Creating new connection to hackage.haskell.org
Received:
HTTP/1.1 404 Not Found
Date: Fri, 21 Nov 2008 23:52:14 GMT
Server: Apache/2.2.3 (Debian)
Alternates: {HTTP_NOT_FOUND.html.var 1 {type text/html} {charset
iso-8859-2} {language cs} {length 745}}, {HTTP_NOT_FOUND.html.var 1
{type text/html} {charset iso-8859-1} {language de} {length 766}},
{HTTP_NOT_FOUND.html.var 1 {type text/html} {charset iso-8859-1}
{language en} {length 611}}, {HTTP_NOT_FOUND.html.var 1 {type
text/html} {charset iso-8859-1} {language es} {length 759}},
{HTTP_NOT_FOUND.html.var 1 {type text/html} {charset iso-8859-1}
{language fr} {length 771}}, {HTTP_NOT_FOUND.html.var 1 {type
text/html} {charset iso-8859-1} {language ga} {length 813}},
{HTTP_NOT_FOUND.html.var 1 {type text/html} {charset iso-8859-1}
{language it} {length 692}}, {HTTP_NOT_FOUND.html.var 1 {type
text/html} {charset iso-2022-jp} {language ja} {length 749}},
{HTTP_NOT_FOUND.html.var 1 {type text/html} {charset euc-kr} {language
ko} {length 703}}, {HTTP_NOT_FOUND.html.var 1 {type text/html}
{charset iso-8859-1} {language nl} {length 688}},
{HTTP_NOT_FOUND.html.var 1 {type text/html} {charset iso-8859-2}
{language pl} {length 707}}, {HTTP_NOT_FOUND.html.var 1 {type
text/html} {charset iso-8859-1} {language pt-br} {length 753}},
{HTTP_NOT_FOUND.html.var 1 {type text/html} {charset iso-8859-1}
{language ro} {length 689}}, {HTTP_NOT_FOUND.html.var 1 {type
text/html} {charset iso-8859-5} {language sr} {length 716}},
{HTTP_NOT_FOUND.html.var 1 {type text/html} {charset iso-8859-1}
{language sv} {length 722}}, {HTTP_NOT_FOUND.html.var 1 {type
text/html} {charset iso-8859-9} {language tr} {length 755}}
Vary: accept-language,accept-charset
Content-Length: 418
Content-Type: text/html; charset=iso-8859-1
cabal: Unrecognised response from server.
[EMAIL PROTECTED]:~$ cabal --version
cabal-install version 0.6.0
using version 1.6.0.1 of the Cabal library
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[Haskell-cafe] How to getCh on MS Windows command line?
What I mean by getCh is the non-buffered non-echoed version of getChar, which Hugs used to provided as an extension but not any more. Is there any way to have a non-buffered non-echoed single character input function on MS Windows command line using only the libraries in the MS Windows distribution packages of either GHC or Hugs? The reason to why this is important for me is because I am translating Graham Hutton's Programming in Haskell into Korean (soon to be published), which illustrates interactive programming with the example of a calculator that responds instantly for every keystroke of numbers and arithmetic operations running on text mode. It is very important to consider the readers who only have access to MS Windows systems, because Korean OS market share is completely skewed towards MS Windows for very embarrassing reasons that I do not even want to mention. And, isn't GHC developed in MSR anyway? :-) I remember that this is an old problem for both of the two most widely used Haskell implementation, Hugs and GHC. In ghc 6.8 getChar had a bit strange behavior. As far as I remember it always worked as if it were NoBuffering. Fortunately, in the recently released ghc 6.10, this has been fixed. We now actually have to set the buffering mode to NoBuffering with hSetBufferring to get the non-buffered behavior of getChar. But, it still isn't working on MS Windows. In Hugs, hSetBuffering neither works on Unix terminal nor on MS Windows command line. Surprisingly, it works in WinHugs. However, I cannot use WinHugs for my purpose because the interactive calculator example in the book also uses beep characters and ANSI codes which do not work in WinHugs. Thanks for any hacks or suggestions, -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] [fun] HaskellDB Talk trailer
There is an impressive HaskellDB Talk trailer on the web. http://www.vimeo.com/1983774 Cheers to the HaskellDB developers :-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] yi compiles but does not launches
I wanted to try out yi after seeing it demonstrated in the Haskell symposium. So, I installed cabal as described here http://hackage.haskell.org/trac/hackage/wiki/CabalInstall I am using Debian unstable with debian distributed GHC 6.8.2.x but it seems that yi requries GHC 6.8.3 to compile. So, I manually installed GHC 6.8.3 using the binary distribution from ghc homepage. When I install yi with cabal install yi it succeeds and installs yi version 0.4.6 However, when I run yi it starts but immediately get stuck with the following error message: Custom yi (/home/kyagrd/.yi/yi-i386-linux) could not be launched! The custom file yi-i386-linux does not exist and I don't have any idea what that is. Same thing happens with the development version 0.4.7 from darcs repository. I did this from complete scratch. I removed the .cabal and .ghc directory and started from scratch in a clean state. If anyone have succeeded using yi in Debian unstable please let me know how you got around from this problem. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] The dark side of lazyness - memory leak
I'm facing the dark side of lazyness recently. Typical pattern is like this. My code was working fine and I was happy. I just wanted to inspect some properties of my code so I made a slight chane go the code such as adding counter argument or attaching axulary data filed to original data for tracing how the data has been constructed. All of a sudden the program runs out of memory or overflows the stack. One problem is that it comes up unexptectedly. Another even worse problem is that sometimes I get no idea for the exact loation causing the leak! It really panics facing such darkness of lazy evaluation. Just a small innocent looking fix for inspection or tracing blow things up, sometime with no clue for its reason. When I put a debugging or tracing operating in my software that can be toggled, how could I be sure that turning on those features won't crash my software written in Haskell? Are there appraoches to detect and fix these kind of problem? Haskell may be type safe but not safe at all from unexpteded diversion, not because of the programmers' mistake but just because of the lazyness. I have posted an wiki article including one example of this dark side of lazyness I encountered when I tried to count the number of basic operations in sorting algorithm. This was a rather simple situation and we figured out how to cure this by self equality check ( x==x ) forcing evaluation. There are wose cases not being able to figure out the cure. I wrote a fucntion for analyzing some property of a graph, which worked fine. fixOnBy t p f x = if t x' `p` t x then x else fixOnBy t p f x' where x' = f x fixSize f x = fixOnBy Set.size (==) f x sctAnal gs = null cgs || all (not . null) dcs where gs' = fixSize compose $ Set.fromList [(x,y,cs) | To _ x y cs-Set.toList gs] cgs = [z | z@(x,y,cs)-Set.toList gs', x==y] dcs = [ [c| c@(a,D,b)-Set.toList cs , a==b] | (_,_,cs)-cgs] compose gs = trace (## ++show (Set.size gs)) $ foldr Set.insert gs $ do (x1,y1,cs1) - Set.toList gs (_,y2,cs2) - takeWhileFst y1 $ Set.toList $ setGT (y1,Al(-1),Set.empty) gs return (x1,y2,cs1 `comp` cs2) takeWhileFst y = takeWhile (\(y',_,_) - y==y') This fucntion makes a transitive closure of the given set of relations by fixpoint iteration on the size of the set of weighted edegs. Sample output is like this. *Main main ## 170 ## 400 ## 1167 ## 2249 ## 2314 False When I add an extra data field for tracing how the new item was made (e.g. tag [a,b,c] on a-c if it was generated by a-b and b-c) It suddenly overflows the stack even before printing out the trace. The following is the code that leaks memory. sctAnal gs = null cgs || all (not . null) dcs where gs' = fixSize compose $ Set.fromList [TT (x,y,cs) [] | To _ x y cs-Set.toList gs] cgs = [z | z@(TT (x,y,cs) _)-Set.toList gs', x==y] dcs = [[c| c@(a,D,b)-Set.toList cs , a==b] | TT (_,_,cs) _-cgs] compose gs = trace (## ++show (Set.size gs)) $ foldr checkInsert gs $ do TT (x1,y1,cs1) l1 - Set.toList gs TT (_,y2,cs2) l2 - takeWhileTTfrom y1 . Set.toList $ setGT (TT (y1,Al(-1),Set.empty) []) gs return $ TT (x1,y2,cs1 `comp` cs2) (l1++y1:l2) takeWhileTTfrom y = takeWhile (\(TT (y',_,_) _) - y==y') checkInsert x s | Set.member x s = s | otherwise = Set.insert x s data TT a b = TT a b deriving (Show) instance (Eq a, Eq b) = Eq (TT a b) where (TT x lx) == (TT y ly) = lx==lx ly==ly x == y instance (Ord a, Ord b) = Ord (TT a b) where (TT x lx) (TT y ly) = lx==lx ly==ly x y The really intersting thing happens when I just make the Ord derived the stack does not overflow and starts to print out the trace. (It is not the result that I want though. My intention is to ignore the tags in the set operation) data TT a b = TT a b deriving (Show,Eq,Ord) I believe my Eq and Ord instances are even more stricter than the derived ones. Is there some magic in deriving that prevents memory leak? I've even followed the instance declaration that would be the same as deriving but the that leaks memory. data TT a b = TT a b deriving (Show) instance (Eq a, Eq b) = Eq (TT a b) where (TT x lx) == (TT y ly) = x == y lx == ly instance (Ord a, Ord b) = Ord (TT a b) where (TT x lx) (TT y ly) = x y || x == y lx ly This is really a panic. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How can we detect and fix memory leak due to lazyness?
Recently, I'm facing the dark side of laziness -- the memory leak because of laziness. Typical pattern that I encounter the problem is like this. My code was working fine and I was happy. I just wanted to inspect some properties of my code so I made a slight chage go the code such as adding counter argument or attaching auxiliary data filed to original data for tracing how the data has been constructed. All of a sudden the program runs out of memory or overflows the stack. One problem is that it comes up unexpectedly. Another even worse problem is that sometimes I get no idea for the exact location causing the leak! It really panics facing such darkness of lazy evaluation. Just a small innocent looking fix for inspection or tracing blow things up, sometime with no clue for its reason. When we implement a debugging or tracing option in the software and let the user toggle those features, how could we be sure that turning on those features won't crash the software written in Haskell? Are there standardized approaches for detecting and fixing these kind of problems? Haskell may be type safe but not safe at all from unexpanded diversion, which is not because of the programmers' mistake but just because of the laziness. I have posted an wiki article including one example of adding a counter to count the number of basic operations in sorting algorithm. http://www.haskell.org/haskellwiki/Physical_equality This was a rather simple situation and we figured out how to cure this by self equality check ( x==x ) forcing evaluation. There are worse cases not being able to figure out the cure. I wrote a function for analyzing some property of a graph, which worked fine. fixOnBy t p f x = if t x' `p` t x then x else fixOnBy t p f x' where x' = f x fixSize f x = fixOnBy Set.size (==) f x sctAnal gs = null cgs || all (not . null) dcs where gs' = fixSize compose $ Set.fromList [(x,y,cs) | To _ x y cs-Set.toList gs] cgs = [z | z@(x,y,cs)-Set.toList gs', x==y] dcs = [ [c| c@(a,D,b)-Set.toList cs , a==b] | (_,_,cs)-cgs] compose gs = trace (## ++show (Set.size gs)) $ foldr Set.insert gs $ do (x1,y1,cs1) - Set.toList gs (_,y2,cs2) - takeWhileFst y1 $ Set.toList $ setGT (y1,Al(-1),Set.empty) gs return (x1,y2,cs1 `comp` cs2) takeWhileFst y = takeWhile (\(y',_,_) - y==y') This function makes a transitive closure of the given set of relations by fixpoint iteration on the size of the set of weighted edges. Sample output is like this. *Main main ## 170 ## 400 ## 1167 ## 2249 ## 2314 False When I add an extra data field for tracing how the new relation was constructed, (e.g. tag [a,b,c] on a-c if it came from a-b and b-c) it suddenly overflows the stack even before printing out the trace. The following is the code that leaks memory. sctAnal gs = null cgs || all (not . null) dcs where gs' = fixSize compose $ Set.fromList [TT (x,y,cs) [] | To _ x y cs-Set.toList gs] cgs = [z | z@(TT (x,y,cs) _)-Set.toList gs', x==y] dcs = [[c| c@(a,D,b)-Set.toList cs , a==b] | TT (_,_,cs) _-cgs] compose gs = trace (## ++show (Set.size gs)) $ foldr checkInsert gs $ do TT (x1,y1,cs1) l1 - Set.toList gs TT (_,y2,cs2) l2 - takeWhileTTfrom y1 . Set.toList $ setGT (TT (y1,Al(-1),Set.empty) []) gs return $ TT (x1,y2,cs1 `comp` cs2) (l1++y1:l2) takeWhileTTfrom y = takeWhile (\(TT (y',_,_) _) - y==y') checkInsert x s | Set.member x s = s | otherwise = Set.insert x s data TT a b = TT a b deriving (Show) instance (Eq a, Eq b) = Eq (TT a b) where (TT x lx) == (TT y ly) = lx==lx ly==ly x == y instance (Ord a, Ord b) = Ord (TT a b) where (TT x lx) (TT y ly) = lx==lx ly==ly x y The really intersting thing happens when I just make the Ord derived the stack does not overflow and starts to print out the trace. (It is not the result that I want though. My intention is to ignore the tags in the set operation) data TT a b = TT a b deriving (Show,Eq,Ord) I believe my Eq and Ord instances defined above are even more stricter than the derived ones. Is there some magic in deriving that prevents memory leak? I've even followed the instance declaration like the following that would be the same as deriving but still leaks memory. data TT a b = TT a b deriving (Show) instance (Eq a, Eq b) = Eq (TT a b) where (TT x lx) == (TT y ly) = x == y lx == ly instance (Ord a, Ord b) = Ord (TT a b) where (TT x lx) (TT y ly) = x y || x == y lx ly This is really a panic. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How can we detect and fix memory leak due to lazyness?
On 8/7/06, Spencer Janssen [EMAIL PROTECTED] wrote:
Forcing evaluation using (==) is a bit of a hack. Luckily, we have a
better function to force evaluation: seq (which has type a - b - b).
seq x y evaluates x to weak head normal form before returning
y.
Let's try another feature of Haskell to force evaluation: strict data
fields. A ! in front of a field in a data declaration signifies
strictness. In the example below, whenever we construct a value with
TT, the second argument is evaluated.
\begin{code}
data TT a b = TT a !b
\end{code}
Perhaps your instances will work correctly with this data declaration?
Surely I've tried that.
Unfortunately seq and the strict data declaration is not helpful in general.
They are only helpful on base values such as Int or Bool.
What they do is just making sure that it is not a thunk.
That is if it was a list it would just evaluate to see the cons cell
but no further.
Someone wrote a deepSeq module for forcing deep evaluation, which is
like doing self equality strictness hack like x==x.
However, we should be able to locate what is the source of the memory
leak to apply such strictness tricks.
I've tried plugging in x==x like hack almost everywhere I could but
still hard to find the right hack.
I think this is one of the most frustrating drawbacks developing
software in lazy languages like Haskell.
I am a fan of lazy langnauge; I like laziness and infinite data
structures and clean semantics.
But this is really painful. We have confidence that Haskell programs are robust.
It seems it is too easy to blow up the memory or overflow the stack
without intention.
--
Ahn, Ki Yung
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[Haskell-cafe] Edison StandardSet has inefficient function implementation
Edision does not yet have all the asymtotic description of its functions. I got the Edision 1.2 source and looked into the code whether the container implementations meet the expected asymtotic bounds. In the module Data.Coll.StandardSet which packages Data.Set, some functions which can be O(log n) is implemented as O(n). Data.Set has a split and splitMember running in O(log n). With those functions we can implement OrdCollX operations like filterLT, filterLE, filterGT, filterGE, partitionLT_GE, partitionLE_GT, partitionLT_GT all in O(log n). However, only partitionLT_GT was O(log n) implemended using split. All other function implmentation just used its axiomaic description using CollX operations like filter and partition, which is O(n). It needs to be fixed. P.S. I haven't checked the darcs version yet. -- Ahn, Ki Yung ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Tutorial for server programming in concurrent Haskell
I've recently started a small tutorial for server programming in concurrent Haskell. http://kyagrd.dyndns.org/wiki/HaskellServerProgramming For newbies in Haskell and/or server programming, there should be an interoductory tutorial with concrete and simple examples before Simon Marlow's papers about web server implementation in Haskell. This tutorial consists of two famous examples, Echo and Chat, with the source code and makefile to be downloaded, compliled and tested right away. I hope this could be some helpt to those who want to start server programming in Haskell. Server programming in modern fucntional language with concurrency support is a real pleasure! You should also try Erlang if you havnt' tried yet. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: erreta, a couple of unimportant missing words :-(
Ahn Ki-yung wrote:
Simple Cat (revisitied)
\begin{code}
import IO
findM f [] = return Nothing
findM f (x:xs) = do { v - x; if f v then return (Just v) else findM f xs }
isLeft (Left _) = True
isLeft _ = False
main = findM (isLeft) (hCat stdin) where hCat h = try (hGetLine h) : hCat h
\end{code}
This is my answer for the question of my own,
which is posted a couple
of days before.
There are mapM, filterM in the Haskell 98 Standard Library.
But why no findM there ?
As you can see from simple cat, it seems quite useful.
I think fildM should be added to the module Monad.
--
Ahn Ki-yung
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Why no findM ? simple Cat revisited
Simple Cat (revisitied)
\begin{code}
import IO
findM f [] = return Nothing
findM f (x:xs) = do { v - x; if f v then return (Just v) else findM f xs }
isLeft (Left _) = True
isLeft _ = False
main = findM (isLeft) (hCat stdin) where hCat h = try (hGetLine h) : hCat h
\end{code}
This is my answer for the question of my own,
which is posted a couple
There are mapM, filterM in the Haskell 98 Standard Library.
But why no findM there ?
As you can see from simple cat, it seems quite useful.
I think fildM should be added to the module Monad.
--
Ahn Ki-yung
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Re: Why no findM ? simple Cat revisited
Jorge Adriano wrote:
Seems to me like the name findM could be misleading
mapM :: (Monad m) = (a - m b) - [a] - m [b]
filterM :: (Monad m) = (a - m Bool) - [a] - m [a]
These take a monadic function and a list of elements. Yours works the other
way around (takes a function and a list of 'monadic elements').
I'd expect the definition of findM to be:
findM' :: (Monad m) = (a - m Bool) - [a] - m (Maybe a)
findM' f [] = return Nothing
findM' f (x:xs) = do { b - f x; if b then return (Just x) else findM' f xs }
This one doesn't serve your purpose though.
J.A.
I appreciate your comment.
I agree that the type of findM should be the one you suggested,
and it still fits my original purpose. It's no more than a step arout.
\begin{code}
import IO
findM f [] = return Nothing
findM f (x:xs) = do { b - f x; if b then return (Just x) else findM f xs }
isLeft (Left _) = True
isLeft _ = False
main = findM (=return.isLeft) (hCat stdin)
where hCat h = try (hGetLine h=putStrLn) : hCat h
\end{code}
I expetct the next Haskell Library Report includes findM.
It's obviously useful.
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simple cat by joining two infinite lists (intput/ouput)
\begin{code}
import IO
findM f [] = return Nothing
findM f (x:xs) = do { b - f x; if b then return (Just x) else findM f xs }
isLeft (Left _) = True
isLeft _ = False
main =
findM (=return.isLeft) $
map (try . uncurry (=)) $
zip (hGetCharS stdin) (hPutCharS stdout)
where
hGetCharS h = hGetChar h : hGetCharS h
hPutCharS h = hPutChar h : hPutCharS h
\end{code}
Joining input list and output list by uncurried =
IO errors such as EOF are enclosed by try.
findM finds those EOF or IO errors.
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1 line simple cat in Haskell
If you are steaming with compicated codes, then how about taking a break.
Let's play with a simple cat.
\begin{code}
main = mapM (=putChar) getCharS where getCharS = getChar:getCharS
\end{code}
Tested with ghc.
Works good except that you get some messages on stderror
because eof is not handled.
How would you suggest to neatly insert the error handling code into ?
P.S.
Instead of coding with C++,
I want to write my server main code like this.
server_main = mapM (=process.reply) where getReqS = getReq:getReqS
Only if I had enough time ... :-p
Using HDirect and so on ...
--
Ahn Ki-yung
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[Fwd: Re: type class VS struct/functor]
Hmm ... How do you solve this in Haskell ? Original Message Subject: Re: type class VS struct/functor Date: Sat, 19 Jan 2002 01:34:32 GMT From: [EMAIL PROTECTED] (Neelakantan Krishnaswami) Reply-To: [EMAIL PROTECTED] Organization: ATT Broadband Newsgroups: comp.lang.functional References: [EMAIL PROTECTED] On Sat, 19 Jan 2002 10:14:22 +0900, =?EUC-KR?B?vsix4r+1?= [EMAIL PROTECTED] wrote: What does ML struct/functor have anything better than type classes ? For the user type classes feels like implicit functor istantiations to specific sturucture, and struct/functor seems just bugglling the user to do more typing which can be automated by using type classes. The advantage of functors shows up when you need to have multiple implementations of a module for a type. For instance, suppose you want to implement a set, and you write the functors (OCaml below): module type EQ = sig type t val eq : t - t - bool end module type SET = sig type elt type set val empty : set val add : elt - set - set val mem : elt - set - bool end module Set(Eq : EQ) : SET with type elt = Eq.t = struct type elt = Eq.t type set = elt list let empty = [] let add elt set = elt :: set let rec mem elt set = match set with | [] - false | x :: xs - if Eq.eq x elt then true else mem elt xs end Now, suppose you want two kinds of sets of string, one of which is case-sensitive and one of which is not. You can easily do this with functors like so module SensitiveCase = struct type t = string let eq s s' = (s = s') end module InsensitiveCase = struct type t = string let eq s s' = (String.lowercase s) = (String.lowercase s') end module SensitiveSet = Set(SensitiveCase) module InsensitiveSet = Set(InsensitiveCase) Each of these Set types takes a string, but the membership test is different. This is an annoying case in Haskell, because you can make a String a member of the Eq typeclass in only one way. However, I think it's true that typeclasses are less verbose in the common case. Personally, I want a language with both typeclasses and functors, so that I can use either as the problem requires. Neel ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
