[Haskell-cafe] Mutable arrays
Hello,
I'm trying to write code that will take a mutable 2D array and normalize it
by dividing all elements by the largest element.
I managed to write code to do this, but it seems overly complex. I could
write something much simpler in Clean or C++. Most likely, my code is
complex because I don't have any experience with mutable arrays in Haskell.
I couldn't find any tutorials on the Internet. I'd be grateful for
suggestions on simplifying the following code. Thanks.
{-# OPTIONS_GHC -fglasgow-exts -fbreak-on-exception #-}
-- normalize_ary This takes a mutable array. Determines the largest
-- element in the array (max_elem) and then divides every element by
-- max_elem.
normalize_ary :: (Num t1,
Num t,
Ix t,
Ix t1,
MArray a e t2,
Ord e,
Fractional e,
Enum t,
Enum t1) =
a (t, t1) e - t2 ()
normalize_ary ary =
do
-- The following two commented out lines of code show my first
-- attempt at determining a value for max_elem. However, this
-- produces a stack overflow.
-- elem_ary - getElems ary
-- let max_elem = foldl1 max elem_ary
max_elem - calc_max_2d_elem ary
max_elem `seq` map_in_place_2d_arr (\x - x / max_elem) ary
map_in_place_2d_arr :: (MArray a e t, Enum t2, Enum t1, Ix t1, Ix t2) =
(e - e) - a (t1, t2) e - t ()
map_in_place_2d_arr fn arr = ret
where
ret = do ((i1,j1),(i2,j2)) - getBounds arr
( mapM_ (\i - do v - readArray arr i
writeArray arr i (fn v) )
[(i,j) | i - [i1..i2], j - [j1..j2]])
calc_max_2d_elem :: (Ord t, MArray a t t1, Ix t2, Ix t3, Num t3, Num t2) =
a (t3, t2) t - t1 t
calc_max_2d_elem arr =
do m - readArray arr (0,0)
(_,(i_max, j_max)) - getBounds arr
let calc_max_loop arr m (i,j)
| j == j_max = return m
| otherwise = do e - readArray arr (i,j)
let m2 = max e m
m2 `seq` calc_max_loop arr m2 nxt_idx
where nxt_idx | i == i_max - 1 = (0,j+1)
| otherwise = (i+1,j)
calc_max_loop arr m (0,0)
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Re: [Haskell-cafe] Mutable arrays
I prerequest your forgiveness if I sound patronizing, I'm just writing
everything that comes to mind.
2008/2/2 Jeff φ [EMAIL PROTECTED]:
{-# OPTIONS_GHC -fglasgow-exts -fbreak-on-exception #-}
-- normalize_ary This takes a mutable array. Determines the largest
-- element in the array (max_elem) and then divides every element by
-- max_elem.
normalize_ary :: (Num t1,
Num t,
Ix t,
Ix t1,
MArray a e t2,
Ord e,
Fractional e,
Enum t,
Enum t1) =
a (t, t1) e - t2 ()
Yagh! Look at that type signature. That looks like it came from
ghci. That type should raise a few alarms, such as the Num t, Num t1.
Why should the indices be numbers? That indicates that your
implementation is not as general as it should be, so maybe try another
method. (Really it's calc_max_2d_elem which is losing that
generality). I usually write my type signatures first, and then let
that guide my implementation. But you will find differing valid
opinions on this list on that issue. Anyway, without further ado,
into the guts we go.
normalize_ary ary =
do
-- The following two commented out lines of code show my first
-- attempt at determining a value for max_elem. However, this
-- produces a stack overflow.
-- elem_ary - getElems ary
-- let max_elem = foldl1 max elem_ary
Hmm, how big is the array? If it's pretty big, that's
understandable. Frankly, it's because foldl sucks: I have never seen
a reason to use it. You should be using the strict variant foldl'
here. (I don't think there is a foldl1'). And that will get rid of
your big function calc_max_2d_elem.
max_elem - calc_max_2d_elem ary
max_elem `seq` map_in_place_2d_arr (\x - x / max_elem) ary
I don't think that max_elem `seq` is doing anything useful here (but
I could be missing something subtle).
Oh and a really low level thing which may or may not make a
difference: floating point division is expensive. You'd be better
off precalculating 1 / max_elem and then multiplying by that instead.
map_in_place_2d_arr :: (MArray a e t, Enum t2, Enum t1, Ix t1, Ix t2) =
(e - e) - a (t1, t2) e - t ()
Another conspicuous type signature. Enum t2, Enum t1 is the red flag
here. It's because you're using [i1..i2] instead of range (i1,i2)
from Data.Ix.
map_in_place_2d_arr fn arr = ret
where
ret = do ((i1,j1),(i2,j2)) - getBounds arr
( mapM_ (\i - do v - readArray arr i
writeArray arr i (fn v) )
[(i,j) | i - [i1..i2], j - [j1..j2]])
This looks pretty good modulo the [i1..i2] I mentioned above. For this
kind of stuff I prefer to use forM_, as it is a more
imperative-looking construct for imperative-looking code (then you can
lose the parentheses around (\i - ...))...
calc_max_2d_elem :: (Ord t, MArray a t t1, Ix t2, Ix t3, Num t3, Num t2) =
a (t3, t2) t - t1 t
calc_max_2d_elem arr =
do m - readArray arr (0,0)
(_,(i_max, j_max)) - getBounds arr
let calc_max_loop arr m (i,j)
| j == j_max = return m
| otherwise = do e - readArray arr (i,j)
let m2 = max e m
m2 `seq` calc_max_loop arr m2 nxt_idx
where nxt_idx | i == i_max - 1 = (0,j+1)
| otherwise = (i+1,j)
calc_max_loop arr m (0,0)
Hopefully we have done away with this thing given the foldl' thing.
There are a lot of implicit assumptions hiding in this code, such as
indices being zero-based integers. Writing your type signature first
would have caught those assumptions, since you wouldn't have had (Num
t3, Num t2) ;-).
Luke
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Re: [Haskell-cafe] Re: Implementing fixed-sized vectors (using datatype algebra?)
On Feb 1, 2008 10:33 PM, Wolfgang Jeltsch [EMAIL PROTECTED] wrote: Actually it would maybe be better to create common high-level interface that could include unary, binary and decimal arithmetic so that the library could be easily reused in other projects (people like Bjorn, seem to be using the unary implementation). I don't know if it would be feasible though. I'd say, let's start with the decimal thing. We can extend our package later if there's a need to do this, can't we? OK, let's do it like that. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mutable arrays
This is my attempt at some nicer code:
maximum' (x:xs) = foldl' max x xs
maximum' _ = undefined
modifyArray :: (MArray a e m, Ix i) = (e - e) - a i e - m ()
modifyArray fn arr = do
bounds - getBounds arr
forM_ (range bounds) (modifyElement fn arr)
modifyElement :: (MArray a e m, Ix i) = (e - e) - a i e - i - m ()
modifyElement fn arr i = do
x - readArray arr i
writeArray arr i (fn x)
normalizeArray :: (MArray a e m, Ix i, Fractional e, Ord e) = a i e - m ()
normalizeArray arr = do
arr_elems - getElems arr
let max_elem = maximum' arr_elems
modifyArray (/max_elem) arr
On 02/02/2008, Jeff φ [EMAIL PROTECTED] wrote:
Hello,
I'm trying to write code that will take a mutable 2D array and normalize
it
by dividing all elements by the largest element.
I managed to write code to do this, but it seems overly complex. I could
write something much simpler in Clean or C++. Most likely, my code is
complex because I don't have any experience with mutable arrays in
Haskell.
I couldn't find any tutorials on the Internet. I'd be grateful for
suggestions on simplifying the following code. Thanks.
{-# OPTIONS_GHC -fglasgow-exts -fbreak-on-exception #-}
-- normalize_ary This takes a mutable array. Determines the largest
-- element in the array (max_elem) and then divides every element by
-- max_elem.
normalize_ary :: (Num t1,
Num t,
Ix t,
Ix t1,
MArray a e t2,
Ord e,
Fractional e,
Enum t,
Enum t1) =
a (t, t1) e - t2 ()
normalize_ary ary =
do
-- The following two commented out lines of code show my first
-- attempt at determining a value for max_elem. However, this
-- produces a stack overflow.
-- elem_ary - getElems ary
-- let max_elem = foldl1 max elem_ary
max_elem - calc_max_2d_elem ary
max_elem `seq` map_in_place_2d_arr (\x - x / max_elem) ary
map_in_place_2d_arr :: (MArray a e t, Enum t2, Enum t1, Ix t1, Ix t2) =
(e - e) - a (t1, t2) e - t ()
map_in_place_2d_arr fn arr = ret
where
ret = do ((i1,j1),(i2,j2)) - getBounds arr
( mapM_ (\i - do v - readArray arr i
writeArray arr i (fn v)
)
[(i,j) | i - [i1..i2], j - [j1..j2]])
calc_max_2d_elem :: (Ord t, MArray a t t1, Ix t2, Ix t3, Num t3, Num t2)
=
a (t3, t2) t - t1 t
calc_max_2d_elem arr =
do m - readArray arr (0,0)
(_,(i_max, j_max)) - getBounds arr
let calc_max_loop arr m (i,j)
| j == j_max = return m
| otherwise = do e - readArray arr (i,j)
let m2 = max e m
m2 `seq` calc_max_loop
arr m2 nxt_idx
where nxt_idx | i == i_max - 1 = (0,j+1)
| otherwise = (i+1,j)
calc_max_loop arr m (0,0)
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Re: [Haskell-cafe] Mutable arrays
Sorry, I was lazy. New maximum':
maximum' = foldl1' max
On 02/02/2008, Rodrigo Queiro [EMAIL PROTECTED] wrote:
This is my attempt at some nicer code:
maximum' (x:xs) = foldl' max x xs
maximum' _ = undefined
modifyArray :: (MArray a e m, Ix i) = (e - e) - a i e - m ()
modifyArray fn arr = do
bounds - getBounds arr
forM_ (range bounds) (modifyElement fn arr)
modifyElement :: (MArray a e m, Ix i) = (e - e) - a i e - i - m ()
modifyElement fn arr i = do
x - readArray arr i
writeArray arr i (fn x)
normalizeArray :: (MArray a e m, Ix i, Fractional e, Ord e) = a i e - m
()
normalizeArray arr = do
arr_elems - getElems arr
let max_elem = maximum' arr_elems
modifyArray (/max_elem) arr
On 02/02/2008, Jeff φ [EMAIL PROTECTED] wrote:
Hello,
I'm trying to write code that will take a mutable 2D array and normalize
it
by dividing all elements by the largest element.
I managed to write code to do this, but it seems overly complex. I
could
write something much simpler in Clean or C++. Most likely, my code is
complex because I don't have any experience with mutable arrays in
Haskell.
I couldn't find any tutorials on the Internet. I'd be grateful for
suggestions on simplifying the following code. Thanks.
{-# OPTIONS_GHC -fglasgow-exts -fbreak-on-exception #-}
-- normalize_ary This takes a mutable array. Determines the largest
-- element in the array (max_elem) and then divides every element by
-- max_elem.
normalize_ary :: (Num t1,
Num t,
Ix t,
Ix t1,
MArray a e t2,
Ord e,
Fractional e,
Enum t,
Enum t1) =
a (t, t1) e - t2 ()
normalize_ary ary =
do
-- The following two commented out lines of code show my first
-- attempt at determining a value for max_elem. However, this
-- produces a stack overflow.
-- elem_ary - getElems ary
-- let max_elem = foldl1 max elem_ary
max_elem - calc_max_2d_elem ary
max_elem `seq` map_in_place_2d_arr (\x - x / max_elem) ary
map_in_place_2d_arr :: (MArray a e t, Enum t2, Enum t1, Ix t1, Ix t2)
=
(e - e) - a (t1, t2) e - t ()
map_in_place_2d_arr fn arr = ret
where
ret = do ((i1,j1),(i2,j2)) - getBounds arr
( mapM_ (\i - do v - readArray arr i
writeArray arr i (fn v)
)
[(i,j) | i - [i1..i2], j - [j1..j2]])
calc_max_2d_elem :: (Ord t, MArray a t t1, Ix t2, Ix t3, Num t3, Num t2)
=
a (t3, t2) t - t1 t
calc_max_2d_elem arr =
do m - readArray arr (0,0)
(_,(i_max, j_max)) - getBounds arr
let calc_max_loop arr m (i,j)
| j == j_max = return m
| otherwise = do e - readArray arr (i,j)
let m2 = max e m
m2 `seq` calc_max_loop
arr m2 nxt_idx
where nxt_idx | i == i_max - 1 = (0,j+1)
| otherwise = (i+1,j)
calc_max_loop arr m (0,0)
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Re: [Haskell-cafe] Re: Implementing fixed-sized vectors (using datatype algebra?)
On Feb 1, 2008 10:32 PM, Wolfgang Jeltsch [EMAIL PROTECTED] wrote: Am Freitag, 1. Februar 2008 13:00 schrieb Alfonso Acosta: On Jan 31, 2008 11:35 PM, Wolfgang Jeltsch [EMAIL PROTECTED] This is essentially what I had in mind. While Oleg's implementation needs a thrusted core, the GADT solution doesn't. True. However using GADTs doesn't allow to internally make use of Arrays, which (tell me if I'm wrong) are likely to be faster than the naive GADT implementation. It depends. My first GADT implementation is equivalent to the [] type and often [] is better than arrays. For example, if you read the contents of a file and process it with maps, filters, etc., [] is likely to give you constant space usage which arrays don't. If you want to lookup elements by index, then arrays are better, of course. For my purpose, it would be fine to use a []-like implementation, I think. For mine it would be fine too. Let's implement our needs and then maybe extend it if someone rants about it. To make it friendlier for the end user I thought about defining aliases for lets say the first 1 numbers using Template Haskell. That could even make error reports friendlier (not sure to what point though). What do you think? I have no clear opinion about that at the moment. Maybe it's okay to use the representation directly. This way, we don't introduce a dependeny on the Template Haskell language extension (which is only supported by GHC), and the actual representation will occur in error messages anyway whenever the message shows a computed number. Well, my EDSL already makes extensive use of TH. So, being selfish, it wouldn't be a problem for me (or any other GHC user) and I think it would make the library much more usable. Just compare f :: List (() :- D1 :- D0 :- D0 :- 1000) Int - List (() :- D1 :- D0 :- D0 :- D0) Int with, let's say f :: List A1000 Int - List A1000 Int Again, if someone complains about the TH dependency, the aliases could be generated by TH but saved statically in a module for each release. So, we'll be making two separate libraries then. We should think about names. What about FixedVector for the vector library and DecTypArith (maybe too long) or DecTypes for the type-level decimal arithmetic library? Alas, there is an inconsistency in naming packages already. Some prefer names which are entirely lowercase, some prefer camel case. I prefer lowercase, with hyphens separating parts of the name. And I also don't like unusual abbreviations like typ (not much shorter than type). To mention arithmetics is not so important. So maybe something like type-level-decimals? Maybe it's better to put different type-level programming things into a single package. Then we could name this package type-level or something similar. We could start with our decimals. Other type-level things could be added later. I already have some code about type-level booleans. It's not very sensible to put these few lines into a separate package. It might be nice if we had a general type-level programming package where I could put this code into. Sounds sensible. However, I would rather prefer something like type-level-comp (from type level computations) or type-level-prog (from type level programming). Type level by itself doesn't describe the functionality of the package. As for the name of the fixed-size list package, I have to say that I don't like the term vector in this context. A vector is actually something with addition and scalar multiplication defined on it. Maybe we should make also this package's scope wider. What about something like safe-data or similar? I think safe-data is a bit too general and might lead to confusion with other safe data packages (namely Mitchell's Safe library). Since the main particularity of the library is that safety properties are achieved via emulating dependent types I think that light-dependent-types (from lightweight dependent types), number-parameterized-data or simply parameterized-data (this is the name I like best) would be more appropiate. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Implementing fixed-sized vectors (using datatype algebra?)
On Feb 2, 2008 2:54 PM, Alfonso Acosta [EMAIL PROTECTED] wrote: Just compare f :: List (() :- D1 :- D0 :- D0 :- 1000) Int - List (() :- D1 :- D0 :- D0 :- D0) Int I meant f :: List (() :- D1 :- D0 :- D0 :- D0) Int - List (() :- D1 :- D0 :- D0 :- D0) Int sorry for the typo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal, GHC, FFI and Visual Studio on Windows
On Fri, 2008-02-01 at 11:42 +, Magnus Therning wrote: Is it possible to get Cabal to use 'cl' (Microsoft's C/C++ compiler shipped with Visual Studio Express)? The problem is to get GHC to use 'cl'. That's a longer term project that GHC HQ are interested in. There's something about it on the GHC dev wiki I think. Don't hold your breath. I've found the Wiki page on using Visual Studio to create a DLL, then convert it to a .a file so that GHC can consume it. I'd rather skip using Visual Studio to build things and just ship a Cabalised package. You can create .dlls without using VS of course, if that's what you're trying to do. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Issues with hsql-sqllite build; errors from the hackage download
On Fri, 2008-02-01 at 17:05 -0500, bbrown wrote: There seems to be an issue with the hsql-sqlite3. Anyone have a fix. Should I use what is from darcs? HSQL is currently unmaintained. Frederik Eaton was considering taking it over: http://www.nabble.com/HSQL-defunct--td14978532.html Gentoo has a fix: http://haskell.org/~gentoo/gentoo-haskell/dev-haskell/hsql-sqlite/hsql-sqlite-1.7.ebuild The code in src_unpack() is replacing the Setup.hs with a default copy and then adding 'extra-libraries: sqlite3' to the .cabal file. Pretty straightforward. This does assume that you have sqlite3 installed in the default global location. You may also like to consider alternatives like HDBC-sqlite3. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Issues with hsql-sqllite build; errors from the hackage download
Just noticed, by the way, that haskelldb doesn't build correctly because it still hasn't updated the cabal for the base split. On the other hand, the development repo (which is 0.11 -- 0.10 is on hackage) builds fine. Are the maintainers planning to get an updated version on hackage? --S On Feb 2, 2008, at 10:16 AM, Duncan Coutts wrote: On Fri, 2008-02-01 at 17:05 -0500, bbrown wrote: There seems to be an issue with the hsql-sqlite3. Anyone have a fix. Should I use what is from darcs? HSQL is currently unmaintained. Frederik Eaton was considering taking it over: http://www.nabble.com/HSQL-defunct--td14978532.html Gentoo has a fix: http://haskell.org/~gentoo/gentoo-haskell/dev-haskell/hsql-sqlite/ hsql-sqlite-1.7.ebuild The code in src_unpack() is replacing the Setup.hs with a default copy and then adding 'extra-libraries: sqlite3' to the .cabal file. Pretty straightforward. This does assume that you have sqlite3 installed in the default global location. You may also like to consider alternatives like HDBC-sqlite3. Duncan ___ 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] Mutable arrays
2008/2/2, Rodrigo Queiro [EMAIL PROTECTED]: Sorry, I was lazy. New maximum': maximum' = foldl1' max Sorry but none of those propositions change the heart of the problem : the list of elements is totally produced before she can be consumed due to the strict monadic (IO or ST) nature of getElems. Thus you get an extraordinary waste of memory as well as resources... To address this I propose this function : foldl1MArray' :: (MArray a e m, Ix i) = (e - e - e) - a i e - m e foldl1MArray' f a = do (l,u) - getBounds a firstElem - readArray a l foldM (\a mb - a `seq` mb = return . f a) firstElem (map (readArray a) (range (l,u))) With this, we can rewrite the original program using the excellent modifyArray from Rodrigo : normalizeArray :: (MArray a e m, Ix i, Fractional e, Ord e) = a i e - m () normalizeArray arr = do max_elem - foldl1MArray' max arr modifyArray (* (1/max_elem)) arr -- Jedaï ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal, GHC, FFI and Visual Studio on Windows
Magnus Therning wrote: Is it possible to get Cabal to use 'cl' (Microsoft's C/C++ compiler shipped with Visual Studio Express)? Duncan Coutts wrote: The problem is to get GHC to use 'cl'. That's a longer term project that GHC HQ are interested in. There's something about it on the GHC dev wiki I think. Don't hold your breath. When using the native code generator only foreign C code must be compiled with a C compiler. Presently Cabal passes C sources that are listed in the 'c-sources' field of a cabal file to GHC. It would be nice to have a Cabal field to specify the compiler for C sources, say 'c-sources-compiler: msvc'. The default would still be gcc, but with a Cabal flag the user would be able to change that to e.g. Sun's C compiler. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: HList error with hFoldr
On Jan 28, 2008 12:45 AM, [EMAIL PROTECTED] wrote: It seems strange that you need the types e and e' (perhaps this is a quirk or a bug of GHC 6.8). With GHC 6.6, I have derived the following instance (Floating f, MetricSpace e f, HFoldr ApplyDistSum Float l1 f, HZip (HCons e l) (HCons e l) (HCons (e,e) l1)) = MetricSpace (HCons e l) f where c `dist` c' = sqrt $ hFoldr ApplyDistSum (0::Float) (hZip c c') which matches my intuitive understanding, and also sufficient to run the given examples. This also works in GHC 6.8. Thanks! When I wrote `I derived with GHC' I meant it literally. First I wrote the instance without any constraints: instance () = MetricSpace (HCons e l) f where c `dist` c' = sqrt $ hFoldr ApplyDistSum (0::Float) (hZip c c') GHC of course complained about many missing constraints. I started adding the constraints from the list of complaints, until GHC was satisfied. This is basically a cut-and-paste job from the Emacs buffer with GHC error messages to the buffer with the code. Wow. I will try this next time I post. Thanks very much. -- Denis ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mutable arrays
On Sat, Feb 02, 2008 at 12:57:47PM +, Rodrigo Queiro wrote: This is my attempt at some nicer code: maximum' (x:xs) = foldl' max x xs maximum' _ = undefined modifyArray :: (MArray a e m, Ix i) = (e - e) - a i e - m () modifyArray fn arr = do bounds - getBounds arr forM_ (range bounds) (modifyElement fn arr) modifyElement :: (MArray a e m, Ix i) = (e - e) - a i e - i - m () modifyElement fn arr i = do x - readArray arr i writeArray arr i (fn x) normalizeArray :: (MArray a e m, Ix i, Fractional e, Ord e) = a i e - m () normalizeArray arr = do arr_elems - getElems arr let max_elem = maximum' arr_elems modifyArray (/max_elem) arr Note that by using getElems, you are throwing away most of the advantages of arrays, since it is strict (it has to be, since it's effectively an IO function and lazy IO is unsound wrt Haskell's normal semantics) and converts the whole thing into a list. If I just had this one bit of code to do, I'd use explicit loop: normalizeArray arr = do b - getBounds arr ; m - findMax b forM_ (range b) (edit m) where findMax (i:is)= findMax' is = readArray arr i findMax' (i:is) !v = findMax' is . max v = readArray arr i findMax' [] !v = return v edit mx i = writeArray arr i . (/mx) = readArray arr i With a little more, I'd probably set the scene with a few array-modifying combinators, inspired by Oleg's left-fold idea: -- yes, I'm passing four arguments to foldr. this is not a mistake. foldA fn ac arr = getBounds arr = \b - foldr (\ i ct acc - ct = fn i ac = readArray arr i) (\_ - return ac) (range b) ac foldAp fn = foldA (\i a b - return (fn a b)) maxA = foldAp max minBound mapA fn ar = foldA (\i _ v - writeArray ar i (fn v)) () ar normalize arr = maxA arr = \ m - mapA (/m) arr Stefan signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal, GHC, FFI and Visual Studio on Windows
On Sat, 2008-02-02 at 18:15 +0100, Felix Martini wrote: Magnus Therning wrote: Is it possible to get Cabal to use 'cl' (Microsoft's C/C++ compiler shipped with Visual Studio Express)? Duncan Coutts wrote: The problem is to get GHC to use 'cl'. That's a longer term project that GHC HQ are interested in. There's something about it on the GHC dev wiki I think. Don't hold your breath. When using the native code generator only foreign C code must be compiled with a C compiler. Presently Cabal passes C sources that are listed in the 'c-sources' field of a cabal file to GHC. It would be nice to have a Cabal field to specify the compiler for C sources, say 'c-sources-compiler: msvc'. The default would still be gcc, but with a Cabal flag the user would be able to change that to e.g. Sun's C compiler. It would be reasonable to use the system C compiler rather than ghc, however we will have to do more work to find what extra include dirs get used and have Cabal pass those. Currently we pass the -package flags to ghc which ghc uses to look up what include dirs those packages add, and then it calls the C compiler with those extra include dirs. Cabal would have to do that itself. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Refactoring from State monad to ST monad, for STUArray
On Sat, 2008-02-02 at 12:33 -0500, Denis Bueno wrote: Is it possible to use the ST monad as a (drop-in) replacement for the State monad in the following situation? If not, is there a best practice for refactoring? I have a bunch of functions that return state actions: type MyState = ... foo1 :: T1 - State MyState a foo2 :: T2 - State MyState a ... foon :: Tn - State MyState a And I'd like to refactor this to use the ST monad, mechanically, if possible. All uses of the MyState inside State are single-threaded. In my application, MyState is a record with 5 or so fields. One of those fields uses a list to keep track of some information, and I'd like to change that to STUArray, because it changes my bottleneck operations from O(n) to O(1). This, of course, requires having the ST monad around, in order to achieve the proper time complexity. Is there an easy way to do this? In the future, should I *start out* with the ST monad if I suspect I'll need to use an imperative data structure for efficiency reasons? I started out with State because I'm modeling a transition system, so it seemed natural. Any advice is appreciated. %s/State MyState/MyMonad s/g type MyState s = ... s ... type MyMonad s = StateT (MyState s) (ST s) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal, GHC, FFI and Visual Studio on Windows
Duncan Coutts wrote: [..] It would be reasonable to use the system C compiler rather than ghc, however we will have to do more work to find what extra include dirs get used and have Cabal pass those. Currently we pass the -package flags to ghc which ghc uses to look up what include dirs those packages add, and then it calls the C compiler with those extra include dirs. Cabal would have to do that itself. Well it sounds like I'll have to settle for a two-step build procedure for the time being. Luckily I managed to recall the existence of CMake just today, so it seems I can make my Haskell-hacking-on-Windows experience somewhat bearable... /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus．therning＠gmail．com http://therning.org/magnus What if I don't want to obey the laws? Do they throw me in jail with the other bad monads? -- Daveman signature.asc Description: OpenPGP digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal, GHC, FFI and Visual Studio on Windows
On Sat, 2008-02-02 at 18:50 +, Magnus Therning wrote: Duncan Coutts wrote: [..] It would be reasonable to use the system C compiler rather than ghc, however we will have to do more work to find what extra include dirs get used and have Cabal pass those. Currently we pass the -package flags to ghc which ghc uses to look up what include dirs those packages add, and then it calls the C compiler with those extra include dirs. Cabal would have to do that itself. Well it sounds like I'll have to settle for a two-step build procedure for the time being. Luckily I managed to recall the existence of CMake just today, so it seems I can make my Haskell-hacking-on-Windows experience somewhat bearable... Just so I'm sure I understand... So you're building a .dll using just C code and then you want to link that in with a Haskell prog that uses that .dll. And it is essential that the C code be built using MS's C compiler and not gcc. Is that right? And you'd like to have the .dll built using Cabal rather than having to hack an external C/Makefile. Or are you just trying to link some C code statically into a haskell program, but it just so happens that this C code relies on being built with MS's C compiler rather than gcc. Perhaps you could clarify what it is you're trying to do (the end goal, just just the minutia) so we can see what feature it is that Cabal is missing that would help your situation. When we figure that out we can file a feature request so it is not forgotten. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Refactoring from State monad to ST monad, for STUArray
You can also do something like the following:
newtype StateST st s a = StateST { internalRunStateST :: ReaderT
(STRef st s) (ST st) a }
instance MonadState s (StateST s st) where
get = ask = readSTRef
put s = ask = \ref - writeSTRef ref s
runStateST :: StateST st s a - s - ST st a
runStateST m s = do
ref - newSTRef s
runReaderT (internalRunStateST m) ref
-- ryan
On Feb 2, 2008 9:05 AM, Derek Elkins [EMAIL PROTECTED] wrote:
On Sat, 2008-02-02 at 12:33 -0500, Denis Bueno wrote:
Is it possible to use the ST monad as a (drop-in) replacement for the
State monad in the following situation? If not, is there a best
practice for refactoring?
I have a bunch of functions that return state actions:
type MyState = ...
foo1 :: T1 - State MyState a
foo2 :: T2 - State MyState a
...
foon :: Tn - State MyState a
And I'd like to refactor this to use the ST monad, mechanically, if
possible. All uses of the MyState inside State are single-threaded.
In my application, MyState is a record with 5 or so fields. One of
those fields uses a list to keep track of some information, and I'd
like to change that to STUArray, because it changes my bottleneck
operations from O(n) to O(1). This, of course, requires having the ST
monad around, in order to achieve the proper time complexity.
Is there an easy way to do this? In the future, should I *start out*
with the ST monad if I suspect I'll need to use an imperative data
structure for efficiency reasons? I started out with State because
I'm modeling a transition system, so it seemed natural.
Any advice is appreciated.
%s/State MyState/MyMonad s/g
type MyState s = ... s ...
type MyMonad s = StateT (MyState s) (ST s)
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Re: [Haskell-cafe] Issues with hsql-sqllite build; errors from the hackage download
Yes. It would be nice to have an updated HSQL release first though. /Björn On Feb 2, 2008 6:07 PM, Sterling Clover [EMAIL PROTECTED] wrote: Just noticed, by the way, that haskelldb doesn't build correctly because it still hasn't updated the cabal for the base split. On the other hand, the development repo (which is 0.11 -- 0.10 is on hackage) builds fine. Are the maintainers planning to get an updated version on hackage? --S On Feb 2, 2008, at 10:16 AM, Duncan Coutts wrote: On Fri, 2008-02-01 at 17:05 -0500, bbrown wrote: There seems to be an issue with the hsql-sqlite3. Anyone have a fix. Should I use what is from darcs? HSQL is currently unmaintained. Frederik Eaton was considering taking it over: http://www.nabble.com/HSQL-defunct--td14978532.html Gentoo has a fix: http://haskell.org/~gentoo/gentoo-haskell/dev-haskell/hsql-sqlite/ hsql-sqlite-1.7.ebuild The code in src_unpack() is replacing the Setup.hs with a default copy and then adding 'extra-libraries: sqlite3' to the .cabal file. Pretty straightforward. This does assume that you have sqlite3 installed in the default global location. You may also like to consider alternatives like HDBC-sqlite3. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Mutable arrays
On Sat, 2 Feb 2008, [ISO-8859-7] Jeff ö wrote: Hello, I'm trying to write code that will take a mutable 2D array and normalize it by dividing all elements by the largest element. Are you sure you need the arrays to be mutable? Maybe it's fast enough to do the copying - it's significantly easier anyway. If all operations run over the whole array, like the normalization, then it's not much a matter speed, but only a matter of memory. That is you need the double amount of memory, because the data can be processed and copied forth and back. You can even reduce this further, if you can come up with an optimizer fusion framework. With immutable arrays you can easily implement let xm = maximum (Array.elems arr) in fmap (/xm) arr Ok, better use the strict maximum' proposed by others in this thread. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] highlighting-kate - syntax highlighting library
Hello all, I've been working on a source code syntax highlighting library. It is now somewhat usable, and help would be welcome in testing it further, so I'm making it publicly available: darcs get http://johnmacfarlane.net/repos/highlighting-kate Currently, the following languages are supported: AdaAsp AwkBash Bibtex C CmakeColdfusion Commonlisp Cpp CssDDiff Djangotemplate Doxygen DtdErlang FortranHaskell Html Java Javadoc Javascript Json Latex LexLiterateHaskell LuaMakefile Matlab Mediawiki Nasm Objectivec Objectivecpp Ocaml Pascal Perl PhpPostscript Prolog Python Ruby Scala Scheme Sgml SqlSqlMysql SqlPostgresql Tcl Texinfo XmlXslt Yacc The parsers for individual languages are automatically generated from Kate syntax definitions. The xml files have been included in the repository, together with the program that converts them to Haskell modules. There's also a standalone program, Highlight, that you can use to test the highlighting. (See README for instructions.) Bug reports and patches are welcome. Note that I don't want to make any manual modifications to the generated modules in Text/Highlighting/Kate/Syntax. Changes should be made either in the source xml files or in the program ParseSyntaxFiles.hs that generates these modules. John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] weird behavior with FFI
I am working on haskell bindings to C functions using FFI. I have a callback function that returns IO (). When I pass in the callback function: foo = printf foo it crashes (is there an easy way to debug this exception using ghc6.8.2?) bot: SilcClient_d1al: uncaught exception however, if I pass in the callback function: foo = do printf foo return () it does not crash. Is this a bug in my bindings? In ghc/ffi? Full code is at: http://www.thenewsh.com/%7Enewsham/silcbot.tgz Tim Newsham http://www.thenewsh.com/~newsham/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Refactoring from State monad to ST monad, for STUArray
Thanks for all the responses. I have never used monad transformers
before, but StateT is welcome and really cool. I didn't even think to
look them up.
I have a follow up question. I eventually get to a point where I have
a value of type (ST s (Maybe (STUArray s Int Int))), and I need
somehow to get rid of the Maybe, so I can call runSTUArray on it. The
function containing this value returns a pure type:
data Solution = Sat (UArray Int Int) | Unsat deriving (Eq)
I've included the function body below, along with a few comments that
hopefully make my problem clear enough. Let me know if there's any
more detail needed:
solve :: StdGen - Cnf - Solution
solve rnd cnf =
-- To solve, we simply take baby steps toward the solution using solveStep,
-- starting with the empty assignment.
Sat . runSTUArray $
do solution - -- this block, as you can see,
-- is the (ST s (STUArray s Int Int)) value
evalStateT (stepToSolution $ do
initialAssignment - lift (newArray (1, numVars cnf) 0)
solveStep initialAssignment)
SC{cnf=cnf, dm=Map.empty, dl=[], bad=Set.empty, rnd=rnd}
case solution of -- `solution' is the (Maybe (STUArray s Int Int)) value
Nothing - error unsat
Just m - return m
Using `error' in the Nothing case is exactly what I'd like to avoid.
How should I improve this?
On Feb 2, 2008 2:57 PM, Ryan Ingram [EMAIL PROTECTED] wrote:
You can also do something like the following:
newtype StateST st s a = StateST { internalRunStateST :: ReaderT
(STRef st s) (ST st) a }
instance MonadState s (StateST s st) where
get = ask = readSTRef
put s = ask = \ref - writeSTRef ref s
runStateST :: StateST st s a - s - ST st a
runStateST m s = do
ref - newSTRef s
runReaderT (internalRunStateST m) ref
-- ryan
On Feb 2, 2008 9:05 AM, Derek Elkins [EMAIL PROTECTED] wrote:
On Sat, 2008-02-02 at 12:33 -0500, Denis Bueno wrote:
Is it possible to use the ST monad as a (drop-in) replacement for the
State monad in the following situation? If not, is there a best
practice for refactoring?
I have a bunch of functions that return state actions:
type MyState = ...
foo1 :: T1 - State MyState a
foo2 :: T2 - State MyState a
...
foon :: Tn - State MyState a
And I'd like to refactor this to use the ST monad, mechanically, if
possible. All uses of the MyState inside State are single-threaded.
In my application, MyState is a record with 5 or so fields. One of
those fields uses a list to keep track of some information, and I'd
like to change that to STUArray, because it changes my bottleneck
operations from O(n) to O(1). This, of course, requires having the ST
monad around, in order to achieve the proper time complexity.
Is there an easy way to do this? In the future, should I *start out*
with the ST monad if I suspect I'll need to use an imperative data
structure for efficiency reasons? I started out with State because
I'm modeling a transition system, so it seemed natural.
Any advice is appreciated.
%s/State MyState/MyMonad s/g
type MyState s = ... s ...
type MyMonad s = StateT (MyState s) (ST s)
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--
Denis
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Re: [Haskell-cafe] Cabal, GHC, FFI and Visual Studio on Windows
Duncan Coutts wrote: [..] Just so I'm sure I understand... Sure thing. Or are you just trying to link some C code statically into a haskell program, but it just so happens that this C code relies on being built with MS's C compiler rather than gcc. Yes, this is exactly it. I mean, I could probably hack the incomplete mingw header files to add the functions I need, but I thought it'd be much easier to just use Microsoft's development environment. Perhaps you could clarify what it is you're trying to do (the end goal, just just the minutia) so we can see what feature it is that Cabal is missing that would help your situation. When we figure that out we can file a feature request so it is not forgotten. The end goal is to sneak Haskell into the work place ;-) What I'd really like to see is the ability to “drive” development completely from Haskell. With that I mean to, just as on Linux, have a single cabal file that compiles the C code containing the wrappers while still having access to a complete development environment. On Windows that means compiling C/C++ with MS's tool set. I hope that clarifies what goes on in my muddy mind a bit... /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus．therning＠gmail．com http://therning.org/magnus What if I don't want to obey the laws? Do they throw me in jail with the other bad monads? -- Daveman signature.asc Description: OpenPGP digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] weird behavior with FFI
Am Samstag, 2. Februar 2008 schrieb Tim Newsham: I am working on haskell bindings to C functions using FFI. I have a callback function that returns IO (). When I pass in the callback function: I suspect this has to do with printf returning 'undefined' if you use it with an IO type. Something in the code looks at the result and crashes. Your second version is equivalent to printf foo = \_ - return (), i.e. it never evaluates printf's result but returns () instead. Fixing the first version would require some changes to Text.Printf, restricting the 'a' in PrintfType (IO a). But the callback function is already of type IO () as mentioned above. HTH, Lukas Tim Newsham http://www.thenewsh.com/~newsham/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Refactoring from State monad to ST monad, for STUArray
Am Samstag, 2. Februar 2008 23:17 schrieb Denis Bueno:
Thanks for all the responses. I have never used monad transformers
before, but StateT is welcome and really cool. I didn't even think to
look them up.
I have a follow up question. I eventually get to a point where I have
a value of type (ST s (Maybe (STUArray s Int Int))), and I need
somehow to get rid of the Maybe, so I can call runSTUArray on it. The
function containing this value returns a pure type:
data Solution = Sat (UArray Int Int) | Unsat deriving (Eq)
I've included the function body below, along with a few comments that
hopefully make my problem clear enough. Let me know if there's any
more detail needed:
solve :: StdGen - Cnf - Solution
solve rnd cnf =
-- To solve, we simply take baby steps toward the solution using
solveStep, -- starting with the empty assignment.
Sat . runSTUArray $
do solution - -- this block, as you can see,
-- is the (ST s (STUArray s Int Int)) value
evalStateT (stepToSolution $ do
initialAssignment - lift (newArray (1, numVars
cnf) 0) solveStep initialAssignment)
SC{cnf=cnf, dm=Map.empty, dl=[], bad=Set.empty, rnd=rnd}
case solution of -- `solution' is the (Maybe (STUArray s Int Int))
value Nothing - error unsat
Just m - return m
Using `error' in the Nothing case is exactly what I'd like to avoid.
How should I improve this?
Would
solve rnd cnf =
case evalStateT ... of
Nothing - Unsat
Just st - Sat $ runSTUArray st
work? Might need some explicit 'forall s.' or not typecheck at all, didn't
test.
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Re: [Haskell-cafe] parsec3 pre-release [attempt 2]
I'm not a fan of parameterizing the Stream class over the monad parameter `m': class Stream s m t | s - t where uncons :: s - m (Maybe (t,s)) which leads to instance declarations like so: instance Monad m = Stream [tok] m tok where uncons [] = return $ Nothing uncons (t:ts) = return $ Just (t,ts) I looked through the sources and I didn't see anywhere where this parameterization gained anything. As a proof of this I did a mechanical re-write removing the class parameter, and the library still seems to work. -Antoine On Feb 1, 2008 11:15 PM, Derek Elkins [EMAIL PROTECTED] wrote: [Now with 100% more correct darcs get URLs.] I'm currently getting Paolo Martini's Google Summer of Code project, an updated version of Parsec, into a releasable state, and I will be maintaining it for at least a while. Paolo's major additions are: * The Parser monad has been generalized into a Parser monad transformer * The parsers have been generalized to work over a stream of any type, in particular, with bytestrings. I have made a few minor additions as well: * There is Haddock documentation for almost all functions * The Parser monad now has Applicative/Alternative instances Currently, I am looking for people to give it a go reporting any bugs in the library or documentation, troubles building it, or changes/features they would like. I'm also interested in performance information. Most old Parsec code should be relatively easy but not trivial to port. There is a darcs repository on code.haskell.org. If nothing comes up, I'll put a package on Hackage in about a week or so. To get the code: darcs get http://code.haskell.org/parsec3 To build it, the standard cabal commands should work: http://haskell.org/haskellwiki/Cabal/How_to_install_a_Cabal_package Alternatively, you can use the cabal-install application: http://hackage.haskell.org/trac/hackage/wiki/CabalInstall The documentation can be generated also via the normal cabal routine, or via cabal-install. The Text.Parsec modules should be preferred to the Text.ParserCombinators.Parsec modules. ___ 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] Circular enums
Hello I'm trying to define functions that allow you to traverse a bounded enumeration, wrapping at the start and the end. My implementation looks like this: next, prev :: (Enum a, Bounded a) = a - a next = turn 1 prev = turn (-1) turn :: (Enum a, Bounded a) = Int - a - a turn n e = toEnum (add (fromEnum (maxBound::a) + 1) (fromEnum e) n) where add mod x y = (x + y + mod) `rem` mod Which fails to type check under GHC with this error: No instance for (Bounded a) arising from use of `maxBound' at Hbot.hs:6:34-41 Probable fix: add (Bounded a) to the expected type of an expression In the expression: maxBound :: a In the first argument of `fromEnum', namely `(maxBound :: a)' In the first argument of `(+)', namely `fromEnum (maxBound :: a)' My (clearly flawed) understanding of the signature I've specified for 'turn' means *exactly* that a is Bounded. Can anyone enlighten me as to where my understanding is going awry and how (whether) I can achieve what I'm trying to do. Thank you Ben ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Circular enums - resend
[Resending with formatting fixed.] Hello I'm trying to define functions that allow you to traverse a bounded enumeration, wrapping at the start and the end. My implementation looks like this: next, prev :: (Enum a, Bounded a) = a - a next = turn 1 prev = turn (-1) turn :: (Enum a, Bounded a) = Int - a - a turn n e = toEnum (add (fromEnum (maxBound::a) + 1) (fromEnum e) n) where add mod x y = (x + y + mod) `rem` mod Which fails to type check under GHC with this error: No instance for (Bounded a) arising from use of `maxBound' at Hbot.hs:6:34-41 Probable fix: add (Bounded a) to the expected type of an expression In the expression: maxBound :: a In the first argument of `fromEnum', namely `(maxBound :: a)' In the first argument of `(+)', namely `fromEnum (maxBound :: a)' My (clearly flawed) understanding of the signature I've specified for 'turn' means *exactly* that a is Bounded. Can anyone enlighten me as to where my understanding is going awry and how (whether) I can achieve what I'm trying to do. Thank you Ben ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Circular enums
On Feb 2, 2008, at 18:41 , Ben Butler-Cole wrote: No instance for (Bounded a) arising from use of `maxBound' at Hbot.hs:6:34-41 (...) My (clearly flawed) understanding of the signature I've specified for 'turn' means *exactly* that a is Bounded. The problem is that the scope of a is the type signature; it does *not* extend to the definition. You can try omitting the type on maxBound and minBound, or you can enable the scoped type variables extension ( http://www.haskell.org/ ghc/docs/latest/html/users_guide/other-type-extensions.html#scoped- type-variables ). -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Circular enums
On Feb 2, 2008, at 18:41 , I wrote: No instance for (Bounded a) arising from use of `maxBound' at Hbot.hs:6:34-41 (...) My (clearly flawed) understanding of the signature I've specified for 'turn' means *exactly* that a is Bounded. Brandon Allbery replied: The problem is that the scope of a is the type signature; it does *not* extend to the definition. You can try omitting the type on maxBound and minBound, or you can enable the scoped type variables extension Thank you. This compiles fine with the Glasgow extensions turned on as long as the type in the function signature is universally quantified: turn :: forall a. (Enum a, Bounded a) = Int - a - a turn n e = toEnum (add (fromEnum (maxBound::a) + 1) (fromEnum e) n) where add mod x y = (x + y + mod) `rem` mod ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] strange GHC assembler failure
I'm getting a weird build error: [ 9 of 95] Compiling Plugin.Pl.Common ( Plugin/Pl/Common.hs, dist/build/lambdabot/lambdabot-tmp/Plugin/Pl/Common.o ) /tmp/ghc52608_0/ghc52608_0.s: Assembler messages: /tmp/ghc52608_0/ghc52608_0.s:36:0: Error: unassigned file number 1 [... more of these ...] I narrowed this down -- this happens when I add my new library silc-client to the Build-depends: line in the cabal file even if none of its code is referenced. Removing the dependency makes the error go away. The module I'm referencing is a new one I'm still working on and it makes use of FFI and references external headers and libraries. (I put a copy at http://www.thenewsh.com/~newsham/silc-client.tgz if it helps anyone debug.. this is not release-quality code though). Any idea what is going on here? Tim Newsham http://www.thenewsh.com/~newsham/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec3 pre-release [attempt 2]
On Sat, 2 Feb 2008, Antoine Latter wrote: I'm not a fan of parameterizing the Stream class over the monad parameter `m': snip I looked through the sources and I didn't see anywhere where this parameterization gained anything. As a proof of this I did a mechanical re-write removing the class parameter, and the library still seems to work. AngloHaskell attendees may remember the quickie I did on handling the layout rule via a parsing monad transformer - removing this would stop me from generating the input stream in a particular monad and break the trick behind it. The idea was to use a lexing monad which the parser would be stacked on top of, such that the parser could communicate with the lexer and delayout function. Then when the parser failed at a point where a closing brace would allow parsing to continue, it could backtrack in the stream, tell the lexer that it failed the first time and ask for the character again - and if the layout rule allows it at that point, the returned character would this time be a closing brace. -- [EMAIL PROTECTED] Performance anxiety leads to premature optimisation ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal, GHC, FFI and Visual Studio on Windows
On Sat, 2008-02-02 at 22:33 +, Magnus Therning wrote: Duncan Coutts wrote: [..] Just so I'm sure I understand... Sure thing. Or are you just trying to link some C code statically into a haskell program, but it just so happens that this C code relies on being built with MS's C compiler rather than gcc. Yes, this is exactly it. I mean, I could probably hack the incomplete mingw header files to add the functions I need, but I thought it'd be much easier to just use Microsoft's development environment. Perhaps you could clarify what it is you're trying to do (the end goal, just just the minutia) so we can see what feature it is that Cabal is missing that would help your situation. When we figure that out we can file a feature request so it is not forgotten. The end goal is to sneak Haskell into the work place ;-) What I'd really like to see is the ability to “drive” development completely from Haskell. With that I mean to, just as on Linux, have a single cabal file that compiles the C code containing the wrappers while still having access to a complete development environment. On Windows that means compiling C/C++ with MS's tool set. I hope that clarifies what goes on in my muddy mind a bit... Ok, so you could create a separate component to produce the .dll / .a from the C code but you'd prefer the convenience of being able to just: c-sources: blah.c and have them included in the project, but built using the MS C compiler. So I think we should file a feature request about building C sources using gcc/ms-c directly rather than going via ghc as that would give us the flexibility to use alternative C compilers. Perhaps you'd like to file it, otherwise I can. http://hackage.haskell.org/trac/hackage/ Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec3 pre-release [attempt 2]
On Feb 2, 2008 5:28 PM, Antoine Latter [EMAIL PROTECTED] wrote: I'm not a fan of parameterizing the Stream class over the monad parameter `m': class Stream s m t | s - t where uncons :: s - m (Maybe (t,s)) which leads to instance declarations like so: instance Monad m = Stream [tok] m tok where uncons [] = return $ Nothing uncons (t:ts) = return $ Just (t,ts) To expand on this point, side-effect instances of Stream don't play nice with the backtracking in Text.Parsec.Prim.try: import Text.Parsec import Text.Parsec.Prim import System.IO import Control.Monad type Parser a = (Stream s m Char) = ParsecT s u m a This particular instance was suggested by Derek. instance Stream Handle IO Char where uncons hdl = do b - hIsEOF hdl if b then return Nothing else liftM (\c - Just (c,hdl)) getChar testParser :: Parser String testParser = try (string hello1) | string hello2 test1 = runPT testParser () stdin stdin = print test2 = hGetLine stdin = print . runP testParser () stdin test1 uses the (Stream Handle IO Char) instance, test2 uses the (Monad m = Stream [a] m a) instance. For input hello2, test2 produces a valid parse while test1 does not. -Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec3 pre-release [attempt 2]
On Sat, 2 Feb 2008, Antoine Latter wrote: To expand on this point, side-effect instances of Stream don't play nice with the backtracking in Text.Parsec.Prim.try: import Text.Parsec import Text.Parsec.Prim import System.IO import Control.Monad type Parser a = (Stream s m Char) = ParsecT s u m a This particular instance was suggested by Derek. snip We've been kicking this around on IRC a little, it took me a moment to remember the problem. Basically the problem isn't parsec/try playing badly with the stream - it's the stream playing badly with parsec/try. You need to keep track of where in the file you are and either cache it in an IORef or use seek to jump about appropriately. At the moment, Derek's instance doesn't know where it is in the stream so Parsec's backtracking is invisible to the underlying monad. That caching is the source of the potential leak I mentioned to you, because Parsec doesn't currently tell the stream when it's committed up to a given point and anything preceding it can be dropped safely. We'll tell the list a nice story about this over the coming week. For now, it's nearly 3am here and I should get to bed! -- [EMAIL PROTECTED] The task of the academic is not to scale great intellectual mountains, but to flatten them. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec3 pre-release [attempt 2]
On Sat, 2008-02-02 at 20:43 -0600, Antoine Latter wrote: On Feb 2, 2008 5:28 PM, Antoine Latter [EMAIL PROTECTED] wrote: I'm not a fan of parameterizing the Stream class over the monad parameter `m': class Stream s m t | s - t where uncons :: s - m (Maybe (t,s)) which leads to instance declarations like so: instance Monad m = Stream [tok] m tok where uncons [] = return $ Nothing uncons (t:ts) = return $ Just (t,ts) To expand on this point, side-effect instances of Stream don't play nice with the backtracking in Text.Parsec.Prim.try: import Text.Parsec import Text.Parsec.Prim import System.IO import Control.Monad type Parser a = (Stream s m Char) = ParsecT s u m a This particular instance was suggested by Derek. instance Stream Handle IO Char where uncons hdl = do b - hIsEOF hdl if b then return Nothing else liftM (\c - Just (c,hdl)) getChar testParser :: Parser String testParser = try (string hello1) | string hello2 test1 = runPT testParser () stdin stdin = print test2 = hGetLine stdin = print . runP testParser () stdin test1 uses the (Stream Handle IO Char) instance, test2 uses the (Monad m = Stream [a] m a) instance. For input hello2, test2 produces a valid parse while test1 does not. Note that instance has a typo in it (which I fixed before testing this myself): getChar should be (hGetChar hdl) (though that makes no difference when you pass in stdin) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: Hlist 0.1 on Hackage
Hey everyone: I'd like to make a short announcement that with the permission of its maintainer, I've uploaded HList v0.1 to Hackage. You can find the Hackage page here: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HList-0.1. 'cabal install HList' should also work. HList for those who don't know is a sort of OO Haskell package which permits heterogeneous lists; you can find out more at http://homepages.cwi.nl/~ralf/HList/. (The Darcs repository is at http://darcs.haskell.org/HList.) What changes have been made to the darcs repo? Well, they are mostly updates and cleanups - I've updated build-depends for GHC 6.8.x; largely moved from -fglasgow-exts to LANGUAGE pragmas; put the modules in a proper module namespace; fixed up Haddock generation; removed some unused files, and other things of that nature. -- gwern Covert data bank Armani Larson Missiles Dick CTP SO13 AUTODIN pgpXMNyRA7zZg.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
