Re: [Haskell-cafe] Handling absent maintainers

[Alexander Dunlap]

One issue that comes up is that when you fork a package, data can no
longer be freely exchanged between libraries using the original
package's datatypes and libraries using the forked package's
datatypes. Something that might help here is the concept of
"extension" or "friend" packages or modules: packages or modules that
could break through to access concrete representations of abstract
datatypes or classes. The advantage would be that in many cases,
instead of forking a package, you could make the necessary changes
through a tightly-coupled but separately-maintained friend package
while still maintaining compatibility with the original package.

This wouldn't help for the problem of maintaining a package that
wouldn't compile. That might be helped by something like a "provides"
or "equivalent" field, where Cabal could be informed that a new
package should be treated as satisfying a dependency on a different
package.

Alex

On Fri, Jul 23, 2010 at 11:36 PM, Mark Wotton  wrote:
> That works fine for my own stuff, but I'd like it to work for people
> using my software that relies on those packages.
>
> mark
>
> On Sat, Jul 24, 2010 at 4:10 PM, Roman Beslik  wrote:
>>  I patch broken packages in my local repository. I increment a version so
>> the local repository get a precedence over the Hackage.
>>
>> On 16.07.10 03:54, Mark Wotton wrote:
>>>
>>> 2. run my own hackage server and tell my users to use that instead.
>>
>> --
>> Best regards,
>>  Roman Beslik.
>>
>>
>
>
>
> --
> A UNIX signature isn't a return address, it's the ASCII equivalent of a
> black velvet clown painting. It's a rectangle of carets surrounding a
> quote from a literary giant of weeniedom like Heinlein or Dr. Who.
>         -- Chris Maeda
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Re: [Haskell-cafe] Handling absent maintainers

[Mark Wotton]

That works fine for my own stuff, but I'd like it to work for people
using my software that relies on those packages.

mark

On Sat, Jul 24, 2010 at 4:10 PM, Roman Beslik  wrote:
>  I patch broken packages in my local repository. I increment a version so
> the local repository get a precedence over the Hackage.
>
> On 16.07.10 03:54, Mark Wotton wrote:
>>
>> 2. run my own hackage server and tell my users to use that instead.
>
> --
> Best regards,
>  Roman Beslik.
>
>



-- 
A UNIX signature isn't a return address, it's the ASCII equivalent of a
black velvet clown painting. It's a rectangle of carets surrounding a
quote from a literary giant of weeniedom like Heinlein or Dr. Who.
        -- Chris Maeda
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[Haskell-cafe] a patch for base.Foreign.C.String, the current locale

[Roman Beslik]

 Hi. I have composed a patch that implements Foreign.C.String according 
to Foreign Function Interface Addendum, i.e. C strings are treated as 
they are encoded with the current locale. Search "Locale.hs" in the 
patch for further directions. Ask if you do not know how to build a 
patched version of the "base" library.

http://www.beroal.in.ua/prg/haskell/locale.patch

--
Best regards,
  Roman Beslik.

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Re: [Haskell-cafe] Handling absent maintainers

[Roman Beslik]

 I patch broken packages in my local repository. I increment a version 
so the local repository get a precedence over the Hackage.


On 16.07.10 03:54, Mark Wotton wrote:

2. run my own hackage server and tell my users to use that instead.


--
Best regards,
  Roman Beslik.

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Re: [Haskell-cafe] Anyone here from New Zealand?

[Ivan Lazar Miljenovic]

Tim Matthews  writes:

> Any of the haskellers here from NZ?
>
> Are you using haskell in production, internally within your company or just
> outside of work in your own time?
>
> In Aus they've got
> hackathonsand user
> groups . Anything
> even remotely similar here in New Zealand?

We actually had two Kiwis (Stephen Blackheath and Hamish Mackenzie) come
along to AusHac; the two of them were talking about having their own
two-man NZ Hackathon when they got back... ;-)

-- 
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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[Haskell-cafe] Weird behavior with arrow commands

[Ronald Guida]

I am trying to figure out how to use GHC's arrow commands, and I found
some extremely weird behavior.

In GHC's manual, there is a description of arrow commands, which I
don't really understand.
http://www.haskell.org/ghc/docs/latest/html/users_guide/arrow-notation.html#id667303
(Primitive Constructs)

I have two questions:
1. What are arrow commands supposed to do?
2. What is this code supposed to do?

-- start of code --

{-# LANGUAGE Arrows #-}
module Main where

import Control.Arrow

foo :: (b -> String) -> b, Int), Float), Double) -> String) -> (b -> String)
foo f g b = f b ++ " " ++ g (((b, 8), 1.0), 6.0)

bar :: (t -> String) -> ((Double, Int) -> String) -> t -> String
bar f g  = proc x -> do
  (f -< x) `foo` \n m -> g -< (n)

main = do
  putStrLn $ foo show show 17
  putStrLn $ bar show show 17
  putStrLn $ foo show show 42
  putStrLn $ bar show show 42

-- end of code --

Output from GHCi:

17 (((17,8),1.0),6.0)
17 (6.730326920298707e-306,0)
42 (((42,8),1.0),6.0)
42 (6.730326920298707e-306,0)

Output after compiling with GHC:

17 (((17,8),1.0),6.0)
17 (5.858736684536801e-270,0)
42 (((42,8),1.0),6.0)
42 (5.858736684536801e-270,0)

GHC Version:
The Glorious Glasgow Haskell Compilation System, version 6.12.3

Thank you
-- Ron
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Re: [Haskell-cafe] Heavy lift-ing

[Alex Stangl]

On Fri, Jul 23, 2010 at 09:12:44PM -0500, aditya siram wrote:
> Lists are non-deterministic, but the function taken by liftM2 does not
> necessarily generate all possible outcomes. In the case of (+) it
> does, not in the case of (-):
> liftM2 (-) [0,1] [2,3] => [0-1,0-2,1-2,1-3] => [-2,-3,-1,-2]
> if all possible cases were generated between the two lists we have to
> include also:
> [2-0,2-1,3-0,3-1]

If I have a - b where a and b are both non-deterministic, I wouldn't
expect to also include in my solution set all the results of b - a.
What if you have a / b? Would you try to include b / a, too, even
though some values of a may be zero?

Alex
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Re: [Haskell-cafe] Heavy lift-ing

[aditya siram]

Lists are non-deterministic, but the function taken by liftM2 does not
necessarily generate all possible outcomes. In the case of (+) it
does, not in the case of (-):
liftM2 (-) [0,1] [2,3] => [0-1,0-2,1-2,1-3] => [-2,-3,-1,-2]
if all possible cases were generated between the two lists we have to
include also:
[2-0,2-1,3-0,3-1]

-deech

On Fri, Jul 23, 2010 at 3:44 PM, Alex Stangl  wrote:
> On Fri, Jul 23, 2010 at 11:43:08AM -0700, michael rice wrote:
>> What does it mean to "promote a function to a monad?"
>>
>> It would seem that the monad values must understand the function that's 
>> being promoted, like Ints understand (+).
>>
>> Prelude Control.Monad> liftM2 (+) (Just 1) (Just 1)
>> Just 2
>>
>> But how does one add [0,1] and [0,2] to get [0,2,1,3]?
>
> It depends upon the semantics of the particular monad. List monads
> represent nondeterminism. So, for example, [0,1] represents a 0 or
> 1, and [0,2] represents a 0 or 2.
>
> When you add 0 or 1 to 0 or 2, your possible answers are [0,2,1,3].
>
> Alex
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Re: [Haskell-cafe] Heavy lift-ing

[Jürgen Doser]

El vie, 23-07-2010 a las 16:35 -0700, michael rice escribió:
> Thanks all,
> 
> Wild, at least up to the "optional" part, which I haven't dug into
> yet.
> 
> So the (+) for the Maybe monad and the (+) for the List monad are one
> in the same, the magic springs from the monads.
> 
> Why is it called "lift"-ing?


g :: m a -> m b -> m c
   /\
  /||\
   ||
   ||
f ::   a ->   b ->   c


liftM2 "lifts" the function f and transforms it into the function g =
liftM2 f. 

Does that picture help?

Jürgen

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Re: [Haskell-cafe] Heavy lift-ing

[Alexander Solla]

On Jul 23, 2010, at 4:35 PM, michael rice wrote:


Why is it called "lift"-ing?


Basically, because mathematicians like enlightening metaphors.  It is  
a mathematical term.


A "monadic value" has an "underlying" value.  To turn a function that  
works on the underlying value into one that works on a monadic value,  
you have to lift it.

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Re: [Haskell-cafe] Heavy lift-ing

[michael rice]

Thanks all,

Wild, at least up to the "optional" part, which I haven't dug into yet.

So the (+) for the Maybe monad and the (+) for the List monad are one in the 
same, the magic springs from the monads.

Why is it called "lift"-ing?

Michael


--- On Fri, 7/23/10, Jürgen Doser  wrote:

From: Jürgen Doser 
Subject: Re: [Haskell-cafe] Heavy lift-ing
To: "michael rice" 
Cc: haskell-cafe@haskell.org
Date: Friday, July 23, 2010, 4:50 PM

El vie, 23-07-2010 a las 15:05 -0400, Nick Bowler escribió:
> On 11:43 Fri 23 Jul     , michael rice wrote:
> [...]
> > But how does one add [0,1] and [0,2] to get [0,2,1,3]?
> 
>
 liftM2 (+) [0,1] [0,2] gives the list
> 
>   [0+0, 0+2, 1+0, 1+2]

which one could have found out by asking ghci:

Prelude Control.Monad> let f a b = show a ++ " + " ++ show b
Prelude Control.Monad> liftM2 f [0,1] [0,2]
["0 + 0","0 + 2","1 + 0","1 + 2"]

or simpler:

Prelude Control.Monad> liftM2 (,) [0,1] [2,3]
[(0,2),(0,3),(1,2),(1,3)]

i.e., the in the list monad, you pair each element of one list with each
element of the other(s).

> (recall that (>>=) in the list monad is concatMap).

(>>=) = flip concatMap, to be precise. Or, concatMap = (=<<)

Now let's have some fun with equational reasoning to see what liftM2
does exactly: (Only read this if you really want to!)

liftM2 f a b 

    = { definition of liftM2 }

do {x <- a; y <- b; return (f x y)}

    = { simplified translation
 of do-notation }

a >>= \x -> (b >>= \y -> return (f x y))

    = { change (>>=) to (=<<) and flip arguments }

(\x -> ((\y -> return (f x y)) =<< b)) =<< a 

    = { specialized to the list monad }

(\x -> ((\y -> [f x y])) `concatMap` b)) `concatMap` a 

    = { change concatMap to prefix application }

concatMap (\x -> concatMap (\y -> [x+y]) b) a

and indeed:

Prelude> concatMap (\x -> concatMap (\y -> [x+y]) [0,2]) [0,1]
[0,2,1,3]

with some effort, I think one can understand what happens here. It
should also be clear how this is generalized to liftM3, liftM4, etc. 

Oh, btw, what about liftM1? Obviously, this should be the following:

liftM1 f a

    = { definition }

do { x <- a ; return f a }
  
    = { same changes as above
 }

concatMap (\x -> [f x]) a

    = { definition of concatMap }

concat (map (\x -> [f x]) a

    = { concating singletons can be simplified } 

map (\x -> f x) a

    = { eta-reduction }

map f a

i.e., liftM1 = map, which is indeed just fmap for lists, as already
pointed out.

You can use this to simplify the last line of the concatMap derivation
above:

concatMap (\x -> concatMap (\y -> [x+y]) b) a

    = { see above }

concatMap (\x -> map (\y -> x+y) b) a

    = { use operator section }

concatMap (\x -> map (x+) b) a

which is about as clear as possible a definition for liftM2 (+)


    Jürgen






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Re: [Haskell-cafe] Heavy lift-ing

[Jürgen Doser]

El vie, 23-07-2010 a las 15:05 -0400, Nick Bowler escribió:
> On 11:43 Fri 23 Jul , michael rice wrote:
> [...]
> > But how does one add [0,1] and [0,2] to get [0,2,1,3]?
> 
> liftM2 (+) [0,1] [0,2] gives the list
> 
>   [0+0, 0+2, 1+0, 1+2]

which one could have found out by asking ghci:

Prelude Control.Monad> let f a b = show a ++ " + " ++ show b
Prelude Control.Monad> liftM2 f [0,1] [0,2]
["0 + 0","0 + 2","1 + 0","1 + 2"]

or simpler:

Prelude Control.Monad> liftM2 (,) [0,1] [2,3]
[(0,2),(0,3),(1,2),(1,3)]

i.e., the in the list monad, you pair each element of one list with each
element of the other(s).

> (recall that (>>=) in the list monad is concatMap).

(>>=) = flip concatMap, to be precise. Or, concatMap = (=<<)

Now let's have some fun with equational reasoning to see what liftM2
does exactly: (Only read this if you really want to!)

liftM2 f a b 

= { definition of liftM2 }

do {x <- a; y <- b; return (f x y)}

= { simplified translation of do-notation }

a >>= \x -> (b >>= \y -> return (f x y))

= { change (>>=) to (=<<) and flip arguments }

(\x -> ((\y -> return (f x y)) =<< b)) =<< a 

= { specialized to the list monad }

(\x -> ((\y -> [f x y])) `concatMap` b)) `concatMap` a 

= { change concatMap to prefix application }

concatMap (\x -> concatMap (\y -> [x+y]) b) a

and indeed:

Prelude> concatMap (\x -> concatMap (\y -> [x+y]) [0,2]) [0,1]
[0,2,1,3]

with some effort, I think one can understand what happens here. It
should also be clear how this is generalized to liftM3, liftM4, etc. 

Oh, btw, what about liftM1? Obviously, this should be the following:

liftM1 f a

= { definition }

do { x <- a ; return f a }
  
= { same changes as above }

concatMap (\x -> [f x]) a

= { definition of concatMap }

concat (map (\x -> [f x]) a

= { concating singletons can be simplified } 

map (\x -> f x) a

= { eta-reduction }

map f a

i.e., liftM1 = map, which is indeed just fmap for lists, as already
pointed out.

You can use this to simplify the last line of the concatMap derivation
above:

concatMap (\x -> concatMap (\y -> [x+y]) b) a

= { see above }

concatMap (\x -> map (\y -> x+y) b) a

= { use operator section }

concatMap (\x -> map (x+) b) a

which is about as clear as possible a definition for liftM2 (+)


Jürgen



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Re: [Haskell-cafe] Heavy lift-ing

[Alex Stangl]

On Fri, Jul 23, 2010 at 11:43:08AM -0700, michael rice wrote:
> What does it mean to "promote a function to a monad?"
> 
> It would seem that the monad values must understand the function that's being 
> promoted, like Ints understand (+).
> 
> Prelude Control.Monad> liftM2 (+) (Just 1) (Just 1)
> Just 2
> 
> But how does one add [0,1] and [0,2] to get [0,2,1,3]?

It depends upon the semantics of the particular monad. List monads
represent nondeterminism. So, for example, [0,1] represents a 0 or
1, and [0,2] represents a 0 or 2.

When you add 0 or 1 to 0 or 2, your possible answers are [0,2,1,3].

Alex
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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 2010.2.0.0

[Andrew Coppin]

Vo Minh Thu wrote:

2010/7/23 Andrew Coppin :
  


Anybody have any theroes why Trend Micro Antivirus is reporting this as a
"confirmed fraud/attack site"?



See here:
http://en.wikipedia.org/wiki/Coral_Content_Distribution_Network#Problems
  


Ah, right. So "confirmed attack site" actually means "it could plausibly 
be an attack site and we can't be bothered to actually check properly"?


Good to know my employers dollers are being well-spent. :-)

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Re: [Haskell-cafe] Heavy lift-ing

[Nick Bowler]

On 11:43 Fri 23 Jul , michael rice wrote:
> Hi,
> 
> I don't understand what's taking place here.
> 
> >From Hoogle:
> 
> =
> 
> liftM2 :: Monad  m => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r
> 
> Promote a function to a monad, scanning the monadic arguments from left to 
> right. For example,
> 
>     liftM2 (+) [0,1] [0,2] = [0,2,1,3]
>     liftM2 (+) (Just 1) Nothing = Nothing
> 
> =
> 
> What does it mean to "promote a function to a monad?"

Consider fmap, which 'promotes a function to a functor':

  fmap :: Functor f => (a -> b) -> f a -> f b

This might be easier to understand if you fully parenthesise this:

  fmap :: Functor f => (a -> b) -> (f a -> f b)

In other words, fmap takes a function on ordinary values as input, and
outputs a function on a particular Functor.

Now consider liftM, which 'promotes a function to a monad':

  liftM :: Monad m => (a -> b) -> m a -> m b

Hey, this looks almost the same as fmap (it is)!  Now, monads have
additional structure which allows us to promote more complicated
functions, for example:

  liftM2 :: Monad m => (a -> b -> c) -> m a -> m b -> m c

which, when fully parenthesised, looks like

  liftM2 :: Monad m => (a -> b -> c) -> (m a -> m b -> m c)

What we have now is that we can promote a 'two argument' function to
Monads (this is not possible on mere Functors, hence there's no fmap2).

> It would seem that the monad values must understand the function
> that's being promoted, like Ints understand (+).

Yes, liftM2 (+) gives you a new function with type
 
  (Num a, Monad m) => m a -> m a -> m a

> But how does one add [0,1] and [0,2] to get [0,2,1,3]?

liftM2 (+) [0,1] [0,2] gives the list

  [0+0, 0+2, 1+0, 1+2]

(recall that (>>=) in the list monad is concatMap).

-- 
Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)
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Re: [Haskell-cafe] Heavy lift-ing

[Albert Y. C. Lai]

On 10-07-23 02:43 PM, michael rice wrote:

liftM2 :: Monad m => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r

[...]

What does it mean to "promote a function to a monad?"


liftM2 f m1 m2 is canned code for

do
  a1 <- m1
  a2 <- m2
  return (f a1 a2)

for example liftM2 f [s,t] [x,y] is [f s x, f s y, f t x, f t y]

liftM2 (++) getLine getLine reads two lines and concatenates them.
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[Haskell-cafe] Heavy lift-ing

[michael rice]

Hi,

I don't understand what's taking place here.

>From Hoogle:

=

liftM2 :: Monad  m => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r

Promote a function to a monad, scanning the monadic arguments from left to 
right. For example,

    liftM2 (+) [0,1] [0,2] = [0,2,1,3]
    liftM2 (+) (Just 1) Nothing = Nothing

=

What does it mean to "promote a function to a monad?"

It would seem that the monad values must understand the function that's being 
promoted, like Ints understand (+).

Prelude Control.Monad> liftM2 (+) (Just 1) (Just 1)
Just 2

But how does one add [0,1] and [0,2] to get [0,2,1,3]?

Michael 



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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 2010.2.0.0

[Vo Minh Thu]

2010/7/23 Andrew Coppin :
> Don Stewart wrote:
>>
>> Download the Haskell Platform 2010.2.0.0:
>>
>>    http://hackage.haskell.org.nyud.net/platform/
>>
>> (Caching server).
>>
>
> Anybody have any theroes why Trend Micro Antivirus is reporting this as a
> "confirmed fraud/attack site"?

See here:
http://en.wikipedia.org/wiki/Coral_Content_Distribution_Network#Problems

Cheers,
Thu
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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 2010.2.0.0

[Don Stewart]

andrewcoppin:
> Don Stewart wrote:
>> Download the Haskell Platform 2010.2.0.0:
>>
>> http://hackage.haskell.org.nyud.net/platform/
>>
>> (Caching server).
>>   
>
> Anybody have any theroes why Trend Micro Antivirus is reporting this as  
> a "confirmed fraud/attack site"?


We're using the Coral Cache caching server, which I guess confuses silly
software.
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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 2010.2.0.0

[Steve Schafer]

On Fri, 23 Jul 2010 18:08:39 +0100, you wrote:

>Anybody have any theroes why Trend Micro Antivirus is reporting this as 
>a "confirmed fraud/attack site"?

Because someone somewhere has used the nyud.net distribution service to
distribute malware. Since it's a free service, it's pretty much
guaranteed that it will have been abused at some point. You can get the
same warnings about tinyurl.com, for example, because people have used
tinyurl.com to direct traffic to malicious web sites.

-Steve
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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 2010.2.0.0

[Andrew Coppin]

Don Stewart wrote:

Download the Haskell Platform 2010.2.0.0:

http://hackage.haskell.org.nyud.net/platform/

(Caching server).
  


Anybody have any theroes why Trend Micro Antivirus is reporting this as 
a "confirmed fraud/attack site"?


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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 2010.2.0.0

[Don Stewart]

Applied, thanks!

leon:
> Some nits, if I may pick (http://hackage.haskell.org/platform/contents.html):
> 
> Under GHC: s/optimzing/optimizing
> Under Alex: Sentence should end with a period.
> Under hsc2hs: There shouldn't be a comma.
> Under haskell code coverage: Testsuite should probably be two words:
> "test suite".
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Re: [Haskell-cafe] Tiger compiler in Haskell: annotating abstract syntax tree

[José Pedro Magalhães]

Hi Romildo,

2010/7/23 José Romildo Malaquias 

> On Tue, Jul 20, 2010 at 09:17:15AM +0200, José Pedro Magalhães wrote:
> >
> > 2010/7/19 José Romildo Malaquias 
> >
> > >
> > > I am writing here to ask suggestions on how to annotate an ast with
> > > types (or any other information that would be relevant in a compiler
> > > phase) in Haskell.
> >
> > Indeed I would suggest the method described in our paper:
> >
> > Martijn van Steenbergen, José Pedro Magalhães, and Johan Jeuring. Generic
> > selections of subexpressions.
> > Paper link: http://dreixel.net/research/pdf/gss_draft.pdf
> > Related hackage package: http://hackage.haskell.org/package/Annotations
>
> Annotations-0.1 requires base ==4.1.* and parsec ==3.0.*, but I have
> base-4.2.0.2 and parsec-3.1.0 on my Gentoo Linux system. Would it work
> with these new versions of base and parsec?
>

Yes, that version has a problem with the constraints. I think they are too
restrictive; probably base >= 4 && base < 4.3 would do. As for parsec, I am
not sure, but at least you can easily get parsec-3.0.*, whereas base is more
complicated. We will upload a new version soon to fix this.


Cheers,
Pedro


>
> Romildo
>
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[Haskell-cafe] Anyone here from New Zealand?

[Tim Matthews]

Any of the haskellers here from NZ?

Are you using haskell in production, internally within your company or just
outside of work in your own time?

In Aus they've got
hackathonsand user
groups . Anything
even remotely similar here in New Zealand?

Thanks

Tim Matthews
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Re: [Haskell-cafe] Tiger compiler in Haskell: annotating abstract syntax tree

[José Romildo Malaquias]

On Tue, Jul 20, 2010 at 09:17:15AM +0200, José Pedro Magalhães wrote:
> 
> 2010/7/19 José Romildo Malaquias 
> 
> >
> > I am writing here to ask suggestions on how to annotate an ast with
> > types (or any other information that would be relevant in a compiler
> > phase) in Haskell.
> 
> Indeed I would suggest the method described in our paper:
> 
> Martijn van Steenbergen, José Pedro Magalhães, and Johan Jeuring. Generic
> selections of subexpressions.
> Paper link: http://dreixel.net/research/pdf/gss_draft.pdf
> Related hackage package: http://hackage.haskell.org/package/Annotations

Annotations-0.1 requires base ==4.1.* and parsec ==3.0.*, but I have
base-4.2.0.2 and parsec-3.1.0 on my Gentoo Linux system. Would it work
with these new versions of base and parsec?

Romildo
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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 2010.2.0.0

[Leon Grynszpan]

Some nits, if I may pick (http://hackage.haskell.org/platform/contents.html):

Under GHC: s/optimzing/optimizing
Under Alex: Sentence should end with a period.
Under hsc2hs: There shouldn't be a comma.
Under haskell code coverage: Testsuite should probably be two words:
"test suite".
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Re: [Haskell-cafe] HaTeX build failure

[Jürgen Doser]

El vie, 23-07-2010 a las 16:53 +0400, Alexey Khudyakov escribió:
> On Fri, Jul 23, 2010 at 4:04 PM, Daniel Díaz  wrote:
> > Hi,
> >
> > I uploaded a package, named HaTeX, to Hackage, but it gets a build failure:
> >
> > Any idea?
> 
> Cabal file has BOM in the beginning. Maybe it make parser choke...

http://hackage.haskell.org/trac/hackage/ticket/533 claims that this bug
is fixed, however, removing the BOM does indeed help here.

Someone will have to fix this on the hackage server, I guess.

Jürgen

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Re: [Haskell-cafe] HaTeX build failure

[Alexey Khudyakov]

On Fri, Jul 23, 2010 at 4:04 PM, Daniel Díaz  wrote:
> Hi,
>
> I uploaded a package, named HaTeX, to Hackage, but it gets a build failure:
>
> Any idea?

Cabal file has BOM in the beginning. Maybe it make parser choke...
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Re: [Haskell-cafe] cabal, Setup.lhs example

[Edward Kmett]

On Fri, Jul 23, 2010 at 8:07 AM, Edward Kmett  wrote:

> That actually runs contrary to one of cabal's other practices, which is to
> add a 'simple' Setup.hs to your package as it makes the sdist is one is not
> present.


er.. I meant "if one is not present."
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Re: [Haskell-cafe] cabal, Setup.lhs example

[Edward Kmett]

That actually runs contrary to one of cabal's other practices, which is to
add a 'simple' Setup.hs to your package as it makes the sdist is one is not
present. With your proposed change, it would then complain about _every_
package that used simple. ;)

Setup.hs exists so that you can execute runhaskell Setup.hs foo instead of
cabal foo. You just need to tell cabal if you want to delegate to Setup.hs,
by using something other than Simple as a build-type. The vast majority of
the users of cabal never bother changing the behavior of Setup.hs.

-Edward Kmett

On Thu, Jul 22, 2010 at 11:58 PM, Mark Wotton  wrote:

> On Fri, Jul 23, 2010 at 12:33 PM, wren ng thornton 
> wrote:
> > Magnus Therning wrote:
> >>
> >> On Thu, Jul 22, 2010 at 11:52, Ross Paterson 
> wrote:
> >>>
> >>> On Thu, Jul 22, 2010 at 11:31:21AM +0100, Magnus Therning wrote:
> 
>  On Thu, Jul 22, 2010 at 10:59, Ross Paterson 
>  wrote:
> >
> > Magnus is building by directly running the Setup.hs himself, which
> > ignores
> > the Build-Type.  To get cabal-install to use his Setup.hs, the
> > Build-Type
> > must be set to Custom.
> 
>  Oh, why*2?
> 
>  Why is the header there if it's not used by Cabal, and why does cabal
>  care?
> >>>
> >>> The field allows cabal to avoid compiling the Setup.hs in this case.
> >>> It might also be used by other tools, e.g. one might only trust Simple
> >>> packages.  Not all fields are used by all tools, and several of them
> >>> do not affect the operation of the library (e.g. Home-page).
> >>
> >> All right, so why would cabal want to avoid compiling the Setup.hs?
> >>
> >> Of course this behaviour of cabal's means that I in the future will use
> >> *Custom*
> >> all the time, since I otherwise have to remember this surprising feature
> >> of a
> >> tool I never use.  Is there any reason *not* to do this?
> >
> > The main reason I could think of to avoid compiling it is for performance
> > reasons. I'm not sure how compelling that is, but...
> >
> > As for why not to always use Custom, as mentioned there are cabal-aware
> > tools out there besides cabal-install. For these other tools, there is a
> big
> > difference between Simple and Custom. With Simple we (ideally) already
> know
> > all the semantics of what Setup.hs does, and so we can wire that into our
> > tools. With Custom we're forced into the position of doing Haskell source
> > analysis since we now have to discover the semantics of an arbitrary
> Turing
> > machine. That's a very high wall to climb if you're just wanting to write
> a
> > simple tool for doing some kind of package analysis.
> >
> > (I don't think the behavior is surprising since I interpret Simple to
> mean
> > that the Setup.hs file is unused/optional. Though clearly YMMV)
>
>
> Ah, this clears up one of my bugs.
>
> Perhaps cabal should print a warning if you have a Setup.hs file,
> _and_ try to use Simple? It'd at least give the hint that they're
> unhappy together.
>
> mark
>
> --
> A UNIX signature isn't a return address, it's the ASCII equivalent of a
> black velvet clown painting. It's a rectangle of carets surrounding a
> quote from a literary giant of weeniedom like Heinlein or Dr. Who.
> -- Chris Maeda
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[Haskell-cafe] HaTeX build failure

[Daniel Díaz]

Hi,

I uploaded a package, named HaTeX, to Hackage, but it gets a build failure:

cabal: Couldn't read cabal file "./HaTeX/1.0.0/HaTeX.cabal

It makes reference to 1.0.0 version, even when building version 1.0.1.

I get the same error when I use cabal install. However, using
configure>build>register I don't have any problem.

I would like this package works well, but I don't know how to solve this
problem. In fact, I don't know what's the problem.

Here a link to the HaTeX package: http://hackage.haskell.org/package/HaTeX

Any idea?
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RE: [Haskell-cafe] cabal, Setup.lhs example

[Sittampalam, Ganesh]

Mark Wotton wrote:

> Perhaps cabal should print a warning if you have a Setup.hs file,
> _and_ try to use Simple? It'd at least give the hint that they're
> unhappy together.  

I think it should instead verify that Setup.hs is consistent with a
Simple build. I don't know how much variation exists, but I believe
"import Distribution.Simple\nmain = defaultMain\n" is all such a
Setup.hs file actually needs.

Ganesh

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Re: [Haskell-cafe] Re: src/Text/XML/HaXml/Lex.hs:(156, 0)-(160, 22): Non-exhaustive patterns in function white

[Malcolm Wallace]

Calls which successfully returned some binary data before do not do so
anymore. The error is:
Prelude.chr: bad argument: 1177427


I can't help with this one.  As Gracjan noted, it is probably because  
your binary data is not valid as UTF-8 text.



Calls which complained about 'white' function now fail with:
precondition not satisfied: Posn.white c | isSpace c


But this one, although likely another symptom of the same binary  
problem, I have fixed in the darcs repo for HaXml.  (Basically, the  
'white' function was only permitting ASCII whitespace - I have now  
extended it to allow for Unicode whitespace characters also.)



Regards,
Malcolm

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[Haskell-cafe] Re: src/Text/XML/HaXml/Lex.hs:(156, 0)-(160, 22): Non-exhaustive patterns in function white

[Gracjan Polak]

Alexander Kotelnikov  myxomop.com> writes:

> 
> > On Wed, 21 Jul 2010 06:46:26 + (UTC)
> > "GP" == Gracjan Polak  gmail.com> wrote:
> GP> 
> GP> Antoine Latter  gmail.com> writes:
> >> Sending off to the maintainer of haxr, although it looks like it might
> >> be in HaXml (from an outside guess).
> GP> 
> GP> Without some real example to look at it will be quite tough to proceed.
> GP> 
> GP> Alexander, can you send that stream of packets to me?
> 
> I attach a stream dump.
> 
> 
> Attachment (poster.dump): application/octet-stream, 2916 bytes
> 
> 

My guess at this point:

Your XML contains PNG as binary data. Since this part is interpreted as a string
with UTF-8 encoding we have big trouble here. Some of byte combinations in PNG
do not constitute correct coding points, are probably converted/normalized and
are interpreted as invalid XML.

Solution: use text-based encoding for binary data. Base64 seems to be obvius
candidate here.

-- 
Gracjan




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RE: [Haskell-cafe] Page rank and GHC docs directory organization

[Sittampalam, Ganesh]

Ketil Malde wrote:
> Robin KAY  writes:
> 
>> the redirects and ignore the original URLs [2]. Using a "302 Found"
>> redirect instead might produce better results, at least for Google
> 
> But the page you point to suggests 302 is discouraged, and says they
> don't help for the other search engines.  Perhaps 'latest' could just
> be a symlink to the latest version instead of a redirect?  
> 
> In addition, all versions could have a blurb saying this is for
> version x.y.z, the latest version can be found (-> url with /latest).
> I believe this should boost the page rank of the 'latest' URL.  

If you both implement 'latest' as a symlink and have this blurb, then
the "latest" page will always have a rather silly looking link to
itself.

If the latest numbered version and latest could be generated separately,
then I think this would work very well.

The quick-n-dirty thing to do would be to switch to the 302 redirects,
which given the dominance of google, may well be good enough.

Ganesh

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Re: [Haskell-cafe] cabal, Setup.lhs example

[Magnus Therning]

On Fri, Jul 23, 2010 at 04:58, Mark Wotton  wrote:
> On Fri, Jul 23, 2010 at 12:33 PM, wren ng thornton  wrote:
>> Magnus Therning wrote:
>>>
>>> On Thu, Jul 22, 2010 at 11:52, Ross Paterson  wrote:

 On Thu, Jul 22, 2010 at 11:31:21AM +0100, Magnus Therning wrote:
>
> On Thu, Jul 22, 2010 at 10:59, Ross Paterson 
> wrote:
>>
>> Magnus is building by directly running the Setup.hs himself, which
>> ignores
>> the Build-Type.  To get cabal-install to use his Setup.hs, the
>> Build-Type
>> must be set to Custom.
>
> Oh, why*2?
>
> Why is the header there if it's not used by Cabal, and why does cabal
> care?

 The field allows cabal to avoid compiling the Setup.hs in this case.
 It might also be used by other tools, e.g. one might only trust Simple
 packages.  Not all fields are used by all tools, and several of them
 do not affect the operation of the library (e.g. Home-page).
>>>
>>> All right, so why would cabal want to avoid compiling the Setup.hs?
>>>
>>> Of course this behaviour of cabal's means that I in the future will use
>>> *Custom*
>>> all the time, since I otherwise have to remember this surprising feature
>>> of a
>>> tool I never use.  Is there any reason *not* to do this?
>>
>> The main reason I could think of to avoid compiling it is for performance
>> reasons. I'm not sure how compelling that is, but...
>>
>> As for why not to always use Custom, as mentioned there are cabal-aware
>> tools out there besides cabal-install. For these other tools, there is a big
>> difference between Simple and Custom. With Simple we (ideally) already know
>> all the semantics of what Setup.hs does, and so we can wire that into our
>> tools. With Custom we're forced into the position of doing Haskell source
>> analysis since we now have to discover the semantics of an arbitrary Turing
>> machine. That's a very high wall to climb if you're just wanting to write a
>> simple tool for doing some kind of package analysis.
>>
>> (I don't think the behavior is surprising since I interpret Simple to mean
>> that the Setup.hs file is unused/optional. Though clearly YMMV)
>
>
> Ah, this clears up one of my bugs.
>
> Perhaps cabal should print a warning if you have a Setup.hs file,
> _and_ try to use Simple? It'd at least give the hint that they're
> unhappy together.

I don't like that idea.  I don't use cabal, so I always need a Setup.hs
whether the Build-Type is Simple or Custom.

This suggestion would also force some tools that don't care about Build-Type
(they just use the Setup.hs irrespective of Build-Type) to start caring.

/M

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Re: [Haskell-cafe] cabal, Setup.lhs example

[Magnus Therning]

On Fri, Jul 23, 2010 at 03:33, wren ng thornton  wrote:
> Magnus Therning wrote:
>>
>> On Thu, Jul 22, 2010 at 11:52, Ross Paterson  wrote:
>>>
>>> On Thu, Jul 22, 2010 at 11:31:21AM +0100, Magnus Therning wrote:

 On Thu, Jul 22, 2010 at 10:59, Ross Paterson 
 wrote:
>
> Magnus is building by directly running the Setup.hs himself, which
> ignores
> the Build-Type.  To get cabal-install to use his Setup.hs, the
> Build-Type
> must be set to Custom.

 Oh, why*2?

 Why is the header there if it's not used by Cabal, and why does cabal
 care?
>>>
>>> The field allows cabal to avoid compiling the Setup.hs in this case.
>>> It might also be used by other tools, e.g. one might only trust Simple
>>> packages.  Not all fields are used by all tools, and several of them
>>> do not affect the operation of the library (e.g. Home-page).
>>
>> All right, so why would cabal want to avoid compiling the Setup.hs?
>>
>> Of course this behaviour of cabal's means that I in the future will use
>> *Custom*
>> all the time, since I otherwise have to remember this surprising feature
>> of a
>> tool I never use.  Is there any reason *not* to do this?
>
> The main reason I could think of to avoid compiling it is for performance
> reasons. I'm not sure how compelling that is, but...
>
> As for why not to always use Custom, as mentioned there are cabal-aware
> tools out there besides cabal-install. For these other tools, there is a big
> difference between Simple and Custom. With Simple we (ideally) already know
> all the semantics of what Setup.hs does, and so we can wire that into our
> tools. With Custom we're forced into the position of doing Haskell source
> analysis since we now have to discover the semantics of an arbitrary Turing
> machine. That's a very high wall to climb if you're just wanting to write a
> simple tool for doing some kind of package analysis.
>
> (I don't think the behavior is surprising since I interpret Simple to mean
> that the Setup.hs file is unused/optional. Though clearly YMMV)

I always thought "Build-Type: Simple" was in some way connected to the
module Distribution.Simple.

/M

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Re: [Haskell-cafe] Page rank and GHC docs directory organization

[Ketil Malde]

Robin KAY  writes:

> the redirects and ignore the original URLs [2]. Using a "302 Found"
> redirect instead might produce better results, at least for Google

But the page you point to suggests 302 is discouraged, and says they
don't help for the other search engines.  Perhaps 'latest' could just be
a symlink to the latest version instead of a redirect?

In addition, all versions could have a blurb saying this is for version
x.y.z, the latest version can be found (-> url with /latest).  I believe
this should boost the page rank of the 'latest' URL.

-k
-- 
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