comp.lang.haskell Google Group

PhD / Postdoc Positions in PLT+AD

2010-03-16T18:00:13Z

Seeking PhD students and postdocs interested in an elegant combination
of functional programming and big-iron style numeric computing.
Functional Programming and Automatic Differentiation
PhD Studentships
Postdoctoral Positions
We are adding exact first-class derivative calculation operators

simple question

2010-03-16T05:05:14Z

hello all
what is wrong with the following? what is the work-around? thanks if
you can help.
peace
stm
data Mark = Ex | Oh deriving (Eq, Show)
data Blank = Blank deriving (Eq, Show)
class Cell a
instance Cell Mark
instance Cell Blank
sameCell :: (Cell a, Cell b) => a -> b -> Bool
sameCell Ex Ex = True

Driving Development with Types and Tests

2010-03-11T15:44:13Z

I'm returning to the Haskell community after a long absence. More on
that later. In working through the Real World Haskell book, I finally
hit [an
exercise]([link]
programming.html) that I found hard:
I'm not sure what made this hard, but I decided to first all specify

Looking for a fast high level language

2010-03-11T14:34:58Z

Hi,
I have been trying to find a computer language that runs no slower
than 3 times C++. I thought that Haskell might be the solution, but,
in my one test case it was about 6 times slower than C++. Can someone
tell me if I am just coding this inefficiently. (Code and run times
below.)
Are there any high level languages that have run times within a

the conceptual and computational similarity of sum, (+) and concat, (++)

2010-03-11T13:11:14Z

I just find it noteworthy that sum and (+) do roughly the same thing
and that (+) could be implemented in terms of sum:
(+) a b = sum [a,b]
Another way to put it is that sum does it work by folding (+)
I was talking with someone in #haskell that felt these related
functions really should have different names.

ghc warning

2010-03-04T14:11:38Z

When I compile
rint :: Int -> Double -> Double
rint d x = fromIntegral (round (x * 10^d)) / 10^d
GHC reports
main.hs:442:25:
Warning: Defaulting the following constraint(s) to type `Integer'
`Integral b' arising from a use of `round' at main.hs:
442:25-40
In the first argument of `fromIntegral', namely

pimp my code

2010-03-04T06:27:10Z

hi all
here is a little module for parsing midi files. it seems to work, but
it's much slower than its python counterpart. maybe somebody could
look through it and see if i'm making any obvious mistakes?
peace
stm
{----------------------------- ------------------------------ ------------------------------ ---

performance question

2010-02-17T17:34:51Z

hi All,
I'm trying to create a simple application, which parses CPP output
files and creates a graphviz dot file. You can find the source here:
[link]
I'm using test files ~25GB as input, the allocation is ~1.5GB. I tried
to profile the application, but found not too much. The (:) allocates

enumerations

2010-02-11T14:19:54Z

hello All,
i tried to tune up my little application, and have found this page:
[link]
but the example does not even compile for me. anyone could give me a
hint how to write enumeration shortly?
thanks,
Laszlo

oohaskell anyone?

2010-02-09T18:46:59Z

hi,
does anybody actually really *use* OOHaskell? like for something long-
lived and not just a home / small research project?
[link]
just curious.

Haskell style

2010-02-06T02:02:05Z

I would like to read some Haskell source code that does a non-trivial
job and that is generally considered to be well-written.
Any suggestions?
Thanks,
Patricia

IDE for Haskell

2010-01-30T18:07:10Z

I'm an experienced programmer, but just starting to learn Haskell and
functional programming. Currently, I'm using GHC, GHCi, with gvim to
edit programs.
I like using IDEs. For example, I do my Java programming in Eclipse. I
do not like Emacs. I first tried it out in about 1984, and I try it
again about once every 5 years, but somehow it just does not suit me.

Problem creating a ForeignPtr

2010-01-28T01:28:06Z

Hi all,
I have this problem with the following snippet:
------------------------------ ---
{-# LANGUAGE ForeignFunctionInterface #-}
import Foreign.Ptr
foreign import ccall "stdlib.h &free"
p_free :: FunPtr (Ptr a -> IO ())
------------------------------ ---
This is a standard example reported verbatim from the GHC documentation of FunPtr:

Function overloading in Haskell

2010-01-27T22:08:34Z

Hi,
Is if possible to overload functions in Haskell similar to that of C++
or C# ? For example, if I want to define a function add which has
multiple arity:
add x y = x + y
add x y z = x + y + z
This doesn't work, the functions need to have different names. After
some googling, I located the following paper by Simon Peyton Jones

newbie question: printed representation for lambdas

2010-01-25T21:04:32Z

Hi
I have
<pre>
*Main> \k -> k + 42
\k -> k + 42
<interactive>:1:0:
No instance for (Show (a -> a))
arising from a use of `print' at <interactive>:1:0-11
Possible fix: add an instance declaration for (Show (a -> a))
In a stmt of a 'do' expression: print it
</pre>
This is understandable, however, is there a way to define a 'show' for