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. Re: Compiling shared (dll) library (Daniel Fischer)
2. Re: FFI export lazy list of string (Edward Z. Yang)
3. Re: FFI export lazy list of string (Alexander.Vladislav.Popov )
----------------------------------------------------------------------
Message: 1
Date: Mon, 5 Dec 2011 15:19:30 +0100
From: Daniel Fischer <[email protected]>
Subject: Re: [Haskell-beginners] Compiling shared (dll) library
To: "Alexander.Vladislav.Popov " <[email protected]>
Cc: [email protected]
Message-ID: <[email protected]>
Content-Type: Text/Plain; charset="utf-8"
On Monday 05 December 2011, 13:44:25, Alexander.Vladislav.Popov wrote:
> > Why the separate compilation? Can't you compile them in one go?
>
> Sorry for a stupid question, how is it?
Not stupid at all.
I'm not an expert in matters FFI, so I don't know if it works in all
situations, but for simple cases at least, you can compile in one go
listing .hs and .c files on the command line.
For a foreign import:
// hsFibo.hs:
{-# LANGUAGE ForeignFunctionInterface #-}
module Main (main) where
import System.Environment (getArgs)
foreign import ccall unsafe "fibo"
c_fibo :: Int -> Int
main :: IO ()
main = do
args <- getArgs
let n = case args of
(a:_) -> read a
_ -> 14
print (c_fibo n)
// Fibonacci.c
int fibo(int n){
int a = (n&1) ? 0 : 1, b = (n&1) ? 1 : 0;
while(n > 1){
a += b;
b += a;
n -= 2;
}
return b;
}
$ ghc -O2 hsFibo.hs Fibonacci.c
[1 of 1] Compiling Main ( hsFibo.hs, hsFibo.o )
Linking hsFibo ...
$ ./hsFibo 21
10946
For a foreign export it's a bit more complicated, as you would have to
generate the .h file(s) first by other means (if all your exported
functions are compatible with the implicit types for C functions [pre C99,
iirc], you can get away without the header, but you'll get warnings about
implicit declarations). But with appropriate headers, you can compile in
one go,
$ ghc -O2 -shared -dynamic -fPIC Export.hs useExport.c -o theexport.so
(if you use a C main to create an executable, also pass -no-hs-main).
>
> And one more question, please: how I can export genexPure :: [String] ->
> [String] to achieve all preferences of lazy list? Not all array at once,
> but to get someting like an iterator, what I can call to get new genex.
Pass. I have no idea how to do that.
------------------------------
Message: 2
Date: Mon, 05 Dec 2011 14:13:07 -0500
From: "Edward Z. Yang" <[email protected]>
Subject: Re: [Haskell-beginners] FFI export lazy list of string
To: "Alexander.Vladislav.Popov" <[email protected]>
Cc: beginners <[email protected]>
Message-ID: <1323112216-sup-8502@ezyang>
Content-Type: text/plain; charset=UTF-8
Hello Alexander,
Your best bet is to make a Haskell functions which gives access to
the head and tail of a list (the head should be converted into a C-friendly
form) and then export them as functions which are callable from C.
http://www.haskell.org/haskellwiki/GHC/Using_the_FFI#Calling_Haskell_from_C
Edward
Excerpts from Alexander.Vladislav.Popov's message of Mon Dec 05 03:08:59 -0500
2011:
> Hi, Haskellers.
>
> Advise me please, how I can export lazy and potentially infinite list of
> string from Haskell program. I think I must call it iteratively: the first
> call initiate some structure and other calls iterate over it, something
> like pair of function `find_first' and `find_next'. And how to marshall
> this structure between programs. Or think in a wrong way? Does any example
> exist how I can make it?
>
> Alexander Popov
------------------------------
Message: 3
Date: Tue, 6 Dec 2011 12:43:58 +0600
From: "Alexander.Vladislav.Popov "
<[email protected]>
Subject: Re: [Haskell-beginners] FFI export lazy list of string
To: "Edward Z. Yang" <[email protected]>
Cc: beginners <[email protected]>
Message-ID:
<calpbq9zlrw+ltoqyb1+pnecyl-hxzbjmn86wdzgrgn0v1zl...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hello Edward,
Would you help me to map this:
-- genexlib.hs
{-# LANGUAGE BangPatterns, ForeignFunctionInterface #-}
module GenexLib where
import Regex.Genex
import System.IO
import System.Environment
data CLazyList a = Empty | CLL !a [a]
instance (Show a) => Show (CLazyList a) where
show Empty = "Empty"
show (CLL x xs) = show x ++ ":.."
next (CLL _ []) = Empty
next (CLL _ (x:xs)) = CLL x xs
fromList [] = Empty
fromList (x:xs) = CLL x xs
open = fromList . genexPure
-- end genexlib.hs
to
-- genex.c
typedef struct CLL {
unsigned char empty;
char *current;
struct CLL *next;
} CLL;
CLL *open(const char *regex);
CLL *next(const CLL *cll);
// void printf(const char *s, ...);
void usage() {
CLL *genex = open("\\d+");
while(!genex->empty) {
printf(genex->current);
genex = next(genex->next);
}
}
-- end genex.c
Alexander Popov
2011/12/6 Edward Z. Yang <[email protected]>
> Hello Alexander,
>
> Your best bet is to make a Haskell functions which gives access to
> the head and tail of a list (the head should be converted into a C-friendly
> form) and then export them as functions which are callable from C.
>
> http://www.haskell.org/haskellwiki/GHC/Using_the_FFI#Calling_Haskell_from_C
>
> Edward
>
> Excerpts from Alexander.Vladislav.Popov's message of Mon Dec 05 03:08:59
> -0500 2011:
> > Hi, Haskellers.
> >
> > Advise me please, how I can export lazy and potentially infinite list of
> > string from Haskell program. I think I must call it iteratively: the
> first
> > call initiate some structure and other calls iterate over it, something
> > like pair of function `find_first' and `find_next'. And how to marshall
> > this structure between programs. Or think in a wrong way? Does any
> example
> > exist how I can make it?
> >
> > Alexander Popov
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20111206/4ac4ef31/attachment-0001.htm>
------------------------------
_______________________________________________
Beginners mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/beginners
End of Beginners Digest, Vol 42, Issue 7
****************************************
