Send Beginners mailing list submissions to
[email protected]
To subscribe or unsubscribe via the World Wide Web, visit
http://www.haskell.org/mailman/listinfo/beginners
or, via email, send a message with subject or body 'help' to
[email protected]
You can reach the person managing the list at
[email protected]
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Beginners digest..."
Today's Topics:
1. scotty + ffi segfault (Miro Karpis)
2. Re: scotty + ffi segfault (Brandon Allbery)
3. Re: scotty + ffi segfault (Miro Karpis)
4. backtracking search and memory usage (Dennis Raddle)
5. Gnome's FLOSS Outreach Program for Women and Google Summer
of Code Opportunities (K?ra)
6. Re: Gnome's FLOSS Outreach Program for Women and Google
Summer of Code Opportunities (Mateusz Kowalczyk)
----------------------------------------------------------------------
Message: 1
Date: Fri, 14 Mar 2014 21:46:48 +0100
From: Miro Karpis <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: [Haskell-beginners] scotty + ffi segfault
Message-ID:
<CAJnnbxHfMktO8jkDJQRhiNdoX3nFX6=b7nWgfTixVUzmb=3...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi, please can you help me with following?
I'm trying to combine scotty + ffi but it returns 'Segmentation
fault/access violation in generated code'.
The thing is, that when I run only the ffi setmodulestring function,
everything works fine. When I call it from scotty I get the segfault. I
have hardcoded the 'param' and 'value' parameters in setmodulestring
function just to be sure that the input is correct.
scotty code:
main = scotty 3000 $ do
middleware logStdoutDev
post "/setstringtest" $ do
let param = "FilePath"
let value = "C:/dev/misc/haskell/services/FM"
result <- liftIO $ FM.setmodulestring param value
text "done"
ffi code:
setmodulestring :: String -> String -> IO CInt
setmodulestring param value = do
cParam <- newCString param
cValue <- newCString value
let cParamLength = fromIntegral $ length param ::CInt
cValueLength = fromIntegral $ length value ::CInt
setVarInArray = (-1)::CInt
result <- c_setmodulestring cParam cParamLength cValue cValueLength
setVarInArray
return result
Any comments/ideas more than appreciated.
Cheers,
Miro
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20140314/d806ec4c/attachment-0001.html>
------------------------------
Message: 2
Date: Fri, 14 Mar 2014 16:52:03 -0400
From: Brandon Allbery <[email protected]>
To: Miro Karpis <[email protected]>, The Haskell-Beginners
Mailing List - Discussion of primarily beginner-level topics related
to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] scotty + ffi segfault
Message-ID:
<CAKFCL4W63NaVXJ9hz7gkSE5=mV-901AfPNOeNm=wW=5thzu...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
On Fri, Mar 14, 2014 at 4:46 PM, Miro Karpis <[email protected]>wrote:
> setmodulestring :: String -> String -> IO CInt
> setmodulestring param value = do
> cParam <- newCString param
> cValue <- newCString value
> let cParamLength = fromIntegral $ length param ::CInt
> cValueLength = fromIntegral $ length value ::CInt
> setVarInArray = (-1)::CInt
> result <- c_setmodulestring cParam cParamLength cValue cValueLength
> setVarInArray
> return result
>
The path you show earlier looks like Windows; you probably want CWString
for Win32 API functions (so newCWString etc.).
--
brandon s allbery kf8nh sine nomine associates
[email protected] [email protected]
unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20140314/e6a9ef9a/attachment-0001.html>
------------------------------
Message: 3
Date: Fri, 14 Mar 2014 22:21:52 +0100
From: Miro Karpis <[email protected]>
To: Brandon Allbery <[email protected]>
Cc: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] scotty + ffi segfault
Message-ID:
<cajnnbxeqe5rmotiactr2ssra6i6jy4jwwgedhgzqx1x3wjj...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
thanks, but also after changing my CString/newCString to
CWString/newCWString I'm getting the segfault. As I mentioned if I run
the setmodulestring
function from ghci everyting works fine (I get proper return value). The
problem only comes if I call setmodulestring from the main.
I have simplified the main here:
main = do
let param = "FilePath"
let value = "C:/dev/misc/haskell/services/FM"
result <- liftIO $ FM.setmodulestring param value
return "done"
Another strange thing is that I can call another external function from the
'main' function without problem.
On Fri, Mar 14, 2014 at 9:52 PM, Brandon Allbery <[email protected]>wrote:
> On Fri, Mar 14, 2014 at 4:46 PM, Miro Karpis <[email protected]>wrote:
>
>> setmodulestring :: String -> String -> IO CInt
>> setmodulestring param value = do
>> cParam <- newCString param
>> cValue <- newCString value
>> let cParamLength = fromIntegral $ length param ::CInt
>> cValueLength = fromIntegral $ length value ::CInt
>> setVarInArray = (-1)::CInt
>> result <- c_setmodulestring cParam cParamLength cValue cValueLength
>> setVarInArray
>> return result
>>
>
> The path you show earlier looks like Windows; you probably want CWString
> for Win32 API functions (so newCWString etc.).
>
> --
> brandon s allbery kf8nh sine nomine
> associates
> [email protected]
> [email protected]
> unix, openafs, kerberos, infrastructure, xmonad
> http://sinenomine.net
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20140314/d375885a/attachment-0001.html>
------------------------------
Message: 4
Date: Fri, 14 Mar 2014 19:06:36 -0700
From: Dennis Raddle <[email protected]>
To: Haskell Beginners <[email protected]>
Subject: [Haskell-beginners] backtracking search and memory usage
Message-ID:
<CAKxLvop6usYGV53u06gN1fPW=2mu2d245ai65v_bo7430kk...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
I want to implement backtracking search, but I wonder if I'm going to
immediately run into memory usage problems if I don't use strict evaluation
somewhere. I'm very hazy on how to implement strict evaluation. I'm
thinking of creating a generic algorithm that looks something like the
following.
We have the concept of a data construct that can be built step by step. At
each step are choices. We are investigating all the choices and finding
series of choices that lead to a completed data construct or "solution." We
want to generate a list of all solutions.
(My Haskell syntax is rusty so there may be errors in the following.)
class Construct a where
enumerateChoices :: a -> [b]
applyChoice :: a -> b -> a
isSolution :: a -> Bool
backtrack :: Construct a => a -> [a]
backtrack c
| isSolution c = [c]
| otherwise =
concat . map (backtrack . applyChoice c) . enumerateChoices $ c
So my question is whether this is going to use a lot of memory to run,
maybe by holding all partially solved data? Where would strict evaluation
go?
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20140314/1908a961/attachment-0001.html>
------------------------------
Message: 5
Date: Sat, 15 Mar 2014 04:52:24 -0400
From: K?ra <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] Gnome's FLOSS Outreach Program for Women
and Google Summer of Code Opportunities
Message-ID:
<CABhyRUjg_m4fP6h9Q18oPvTwX0Kb9vXfMmSGAdXLp=6x-gj...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Are there any participating organizations in OPW or GSoC providing
opportunities to gain Haskell experience? It would be great to see more
Haskell projects participate in this
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20140315/a3f8ebd9/attachment-0001.html>
------------------------------
Message: 6
Date: Sat, 15 Mar 2014 10:16:00 +0000
From: Mateusz Kowalczyk <[email protected]>
To: [email protected]
Subject: Re: [Haskell-beginners] Gnome's FLOSS Outreach Program for
Women and Google Summer of Code Opportunities
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8
On 15/03/14 08:52, K?ra wrote:
> Are there any participating organizations in OPW or GSoC providing
> opportunities to gain Haskell experience? It would be great to see more
> Haskell projects participate in this
>
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
Haskell is part of GSoC this year if that's what you're asking. We're
currently at the proposal stage. No idea about OPW.
--
Mateusz K.
------------------------------
Subject: Digest Footer
_______________________________________________
Beginners mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/beginners
------------------------------
End of Beginners Digest, Vol 69, Issue 18
*****************************************
