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Today's Topics:
1. Re: associative arrays (Adrien Haxaire)
2. Re: Are tuples really needed? (David McBride)
3. "system" call uses a different shell, or does not pick up
the whole environment (Hong Yang)
4. Re: "system" call uses a different shell, or does not pick
up the whole environment (Brent Yorgey)
5. Re: "system" call uses a different shell, or does not pick
up the whole environment (Hong Yang)
6. Re: "system" call uses a different shell, or does not pick
up the whole environment (Michael Orlitzky)
----------------------------------------------------------------------
Message: 1
Date: Tue, 28 Aug 2012 14:29:16 +0200
From: Adrien Haxaire <[email protected]>
Subject: Re: [Haskell-beginners] associative arrays
To: <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8; format=flowed
On Sat, 25 Aug 2012 09:11:30 -0600, Nick Vanderweit wrote:
> I'd still recommend Data.Map, since it's a much more efficient data
> structure
> for the task.
They are implemented as a tree, which is fine as long as you do not
want/need duplicates in your association list.
They are also well documented and the extensive API will do most of
what you'll need. I use them a lot.
--
Adrien Haxaire
www.adrienhaxaire.org | @adrienhaxaire
------------------------------
Message: 2
Date: Tue, 28 Aug 2012 10:23:50 -0400
From: David McBride <[email protected]>
Subject: Re: [Haskell-beginners] Are tuples really needed?
To: "Carlos J. G. Duarte" <[email protected]>
Cc: [email protected]
Message-ID:
<CAN+Tr40Bf=UOv-cP00K-1UWxy=zh9Me=qwk-hzgcs1vlkmy...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Pattern matching makes tuples really useful. Sometimes you just want to
return a pair of values and you don't feel like making a one off
constructor for it.
Eg: random :: (RandomGen g, Random a) => g -> (a, g). Without tuples you'd
have to have a one off type data RandomGenWithRandom g a = RGWR g a, which
is overkill, when you just wanted two values.
On Mon, Aug 27, 2012 at 9:47 PM, Carlos J. G. Duarte <
[email protected]> wrote:
> Sorry if this question is too insane, but I was wondering if tuples are
> really needed in Haskell. I mean, could tuples be generally replaced by
> variables unroll (f x y z) and explicit data types, or are there some
> things only possible to do via tuples?
>
> Thx in advance (and sorry if this looks silly).
>
>
> ______________________________**_________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/**mailman/listinfo/beginners<http://www.haskell.org/mailman/listinfo/beginners>
>
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Message: 3
Date: Tue, 28 Aug 2012 09:58:16 -0500
From: Hong Yang <[email protected]>
Subject: [Haskell-beginners] "system" call uses a different shell, or
does not pick up the whole environment
To: [email protected]
Message-ID:
<CA+_A4U5du4CTW=d+gq-hb4b7hz-vbmxlxsidukobobpbofl...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi,
I am trying to mimic mapM() at shell command line. I define the interface
as "mapm cmd2 cmd1," so cmd2 will be run for each of the cmd1 results. "$_"
can be used inside cmd2 to represent the current cmd1 result.
For example, the command
mapm 'cp -pr $_ destination_dir/$_' ls
copies everything under the current directory to the destination directory.
The code is as follows:
--
module Main where
import System.Environment ( getArgs )
import System.Exit
import System.IO
import System.Process
import Text.Regex
import Text.Regex.Posix
main = do
hs_argv <- getArgs
if length hs_argv /= 2
then
putStrLn "wrong arguments!" >> exitFailure
else do
let [cmd2, cmd1] = hs_argv
(_, hOut, hErr, _) <- runInteractiveCommand cmd1
err <- hGetContents hErr
hClose hErr
if null err
then do
out <- hGetContents hOut
mapM (f cmd2) (lines out)
else
putStr err >> exitFailure
f :: String -> String -> IO ExitCode
f cmd2 item = system cmd2'
where cmd2' = if cmd2 =~ "\\$\\_"::Bool
then subRegex (mkRegex "\\$\\_") cmd2 item
else cmd2
--
It works, except one issue that is bothering me.
If I issue
mapm 'lt $_' ls,
I get a bunch of
/bin/sh: lt: command not found,
while I expect it act the same as
mapm 'ls -Alrt --color=auto $_' ls,
because "lt" is aliased to "ls -Alrt --color=auto."
Notice "/bin/sh" above. My shell is actually tcsh. All the aliases are in
~/.cshrc.
I tried replacing "system cmd2'" with
system ("source ~/.cshrc; " ++ cmd2')
and
system ("tcsh -c " ++ "'source ~/.cshrc; " ++ cmd2' ++ "'"),
but they did not solve the problem.
Can someone please help me?
Thanks,
Hong
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Message: 4
Date: Tue, 28 Aug 2012 11:08:04 -0400
From: Brent Yorgey <[email protected]>
Subject: Re: [Haskell-beginners] "system" call uses a different shell,
or does not pick up the whole environment
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
I do not know the solution to your problem -- dealing with shells,
environments, etc. can be tricky.
However, do you know about the 'xargs' command? E.g. your example
could be accomplished with
ls | xargs -L 1 -I{} cp -pr {} destination_dir/{}
-Brent
On Tue, Aug 28, 2012 at 09:58:16AM -0500, Hong Yang wrote:
> Hi,
>
> I am trying to mimic mapM() at shell command line. I define the interface
> as "mapm cmd2 cmd1," so cmd2 will be run for each of the cmd1 results. "$_"
> can be used inside cmd2 to represent the current cmd1 result.
>
> For example, the command
> mapm 'cp -pr $_ destination_dir/$_' ls
> copies everything under the current directory to the destination directory.
>
> The code is as follows:
>
> --
> module Main where
>
> import System.Environment ( getArgs )
> import System.Exit
> import System.IO
> import System.Process
> import Text.Regex
> import Text.Regex.Posix
>
> main = do
> hs_argv <- getArgs
> if length hs_argv /= 2
> then
> putStrLn "wrong arguments!" >> exitFailure
> else do
> let [cmd2, cmd1] = hs_argv
> (_, hOut, hErr, _) <- runInteractiveCommand cmd1
> err <- hGetContents hErr
> hClose hErr
> if null err
> then do
> out <- hGetContents hOut
> mapM (f cmd2) (lines out)
> else
> putStr err >> exitFailure
>
> f :: String -> String -> IO ExitCode
> f cmd2 item = system cmd2'
> where cmd2' = if cmd2 =~ "\\$\\_"::Bool
> then subRegex (mkRegex "\\$\\_") cmd2 item
> else cmd2
> --
>
> It works, except one issue that is bothering me.
>
> If I issue
> mapm 'lt $_' ls,
> I get a bunch of
> /bin/sh: lt: command not found,
> while I expect it act the same as
> mapm 'ls -Alrt --color=auto $_' ls,
> because "lt" is aliased to "ls -Alrt --color=auto."
>
> Notice "/bin/sh" above. My shell is actually tcsh. All the aliases are in
> ~/.cshrc.
>
> I tried replacing "system cmd2'" with
> system ("source ~/.cshrc; " ++ cmd2')
> and
> system ("tcsh -c " ++ "'source ~/.cshrc; " ++ cmd2' ++ "'"),
> but they did not solve the problem.
>
> Can someone please help me?
>
> Thanks,
>
> Hong
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
------------------------------
Message: 5
Date: Tue, 28 Aug 2012 10:19:58 -0500
From: Hong Yang <[email protected]>
Subject: Re: [Haskell-beginners] "system" call uses a different shell,
or does not pick up the whole environment
To: Brent Yorgey <[email protected]>
Cc: [email protected]
Message-ID:
<CA+_A4U7L8zug5=ofnaz_qspcsukorjdhkaevoxztiwrd6mv...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi Brent,
Thanks for the xargs command info. I did not know it before.
The other reason I want to play with my mapm version is eventually I want
to make it concurrent.
Thanks again,
Hong
On Tue, Aug 28, 2012 at 10:08 AM, Brent Yorgey <[email protected]>wrote:
> I do not know the solution to your problem -- dealing with shells,
> environments, etc. can be tricky.
>
> However, do you know about the 'xargs' command? E.g. your example
> could be accomplished with
>
> ls | xargs -L 1 -I{} cp -pr {} destination_dir/{}
>
> -Brent
>
> On Tue, Aug 28, 2012 at 09:58:16AM -0500, Hong Yang wrote:
> > Hi,
> >
> > I am trying to mimic mapM() at shell command line. I define the interface
> > as "mapm cmd2 cmd1," so cmd2 will be run for each of the cmd1 results.
> "$_"
> > can be used inside cmd2 to represent the current cmd1 result.
> >
> > For example, the command
> > mapm 'cp -pr $_ destination_dir/$_' ls
> > copies everything under the current directory to the destination
> directory.
> >
> > The code is as follows:
> >
> > --
> > module Main where
> >
> > import System.Environment ( getArgs )
> > import System.Exit
> > import System.IO
> > import System.Process
> > import Text.Regex
> > import Text.Regex.Posix
> >
> > main = do
> > hs_argv <- getArgs
> > if length hs_argv /= 2
> > then
> > putStrLn "wrong arguments!" >> exitFailure
> > else do
> > let [cmd2, cmd1] = hs_argv
> > (_, hOut, hErr, _) <- runInteractiveCommand cmd1
> > err <- hGetContents hErr
> > hClose hErr
> > if null err
> > then do
> > out <- hGetContents hOut
> > mapM (f cmd2) (lines out)
> > else
> > putStr err >> exitFailure
> >
> > f :: String -> String -> IO ExitCode
> > f cmd2 item = system cmd2'
> > where cmd2' = if cmd2 =~ "\\$\\_"::Bool
> > then subRegex (mkRegex "\\$\\_") cmd2 item
> > else cmd2
> > --
> >
> > It works, except one issue that is bothering me.
> >
> > If I issue
> > mapm 'lt $_' ls,
> > I get a bunch of
> > /bin/sh: lt: command not found,
> > while I expect it act the same as
> > mapm 'ls -Alrt --color=auto $_' ls,
> > because "lt" is aliased to "ls -Alrt --color=auto."
> >
> > Notice "/bin/sh" above. My shell is actually tcsh. All the aliases are in
> > ~/.cshrc.
> >
> > I tried replacing "system cmd2'" with
> > system ("source ~/.cshrc; " ++ cmd2')
> > and
> > system ("tcsh -c " ++ "'source ~/.cshrc; " ++ cmd2' ++ "'"),
> > but they did not solve the problem.
> >
> > Can someone please help me?
> >
> > Thanks,
> >
> > Hong
>
> > _______________________________________________
> > Beginners mailing list
> > [email protected]
> > http://www.haskell.org/mailman/listinfo/beginners
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
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------------------------------
Message: 6
Date: Tue, 28 Aug 2012 11:35:50 -0400
From: Michael Orlitzky <[email protected]>
Subject: Re: [Haskell-beginners] "system" call uses a different shell,
or does not pick up the whole environment
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8
On 08/28/12 11:19, Hong Yang wrote:
> Hi Brent,
>
> Thanks for the xargs command info. I did not know it before.
>
> The other reason I want to play with my mapm version is eventually I
> want to make it concurrent.
>
GNU Parallel is essentially xargs, run in parallel:
http://www.gnu.org/software/parallel/
Might solve your problem albeit not in Haskell.
------------------------------
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