- Beginners - Haskell.org

What's the difference between "operator" and "function"?
by Costello, Roger L. 10 Oct '11

10 Oct '11

Hi Folks, In a book that I am reading the author distinguishes between "operator" and "function." Example: The "+" is an operator. The "map" is a function. What's the difference between operator and function? /Roger

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Fwd: Real World Haskell: From Portable to System.Win32
by Paulo M. Pocinho 09 Oct '11

09 Oct '11

createFile is probably what I should be looking for. As a side note, I really think this is not a big deal. The portable code is a lot better. I wonder if that exercise was a pun on working with Haskell code just to step back into foul territory. And yes, extra careful on the parameters, or it may end up corrupting other files, launch the missiles and whatnot. One thing I noticed so far using Haskell, usually I have to spend more time thinking before hitting the keyboard. Yet the code is always elegant. Meanwhile, I've been taking a peek inside System.IO.HVFS from MissingH [1]. Looks nice. Thanks for the replies. Cheers! -- [1] http://hackage.haskell.org/packages/archive/MissingH/1.1.1.0/doc/html/Syste… On 8 October 2011 20:34, Henk-Jan van Tuyl <hjgtuyl(a)chello.nl> wrote: > On Sat, 08 Oct 2011 18:45:43 +0200, Chaddaï Fouché > <chaddai.fouche(a)gmail.com> wrote: > >> On Sat, Oct 8, 2011 at 7:47 AM, Paulo Pocinho <pocinho(a)gmail.com> wrote: >>> >>> getFileTime :: HANDLE -> IO (FILETIME, FILETIME, FILETIME) >>> >>> I suppose that means getFileTime takes a file handle (with type >>> HANDLE) and returns an IO type with CreationTime LastAccessTime >>> LastWriteTime [3]. >>> >>> The thing is I don't know how to get a HANDLE type. I understand I can >>> get a file handle by opening it. I've been trying the following: >>> >>> openFile :: FilePath -> IOMode -> IO Handle >>> fh <- openFile "myfile.hs" ReadMode >>> >> >> Yes, the case is significant and that means that Handle and HANDLE >> aren't the same, apparently HANDLE is specific to the win32 api (which >> I don't know well), a rapid inspection of System.Win32.File seems to >> reveal that the only function to get an HANDLE is createFile which has >> a ton of parameters you'll need to set carefully to avoid overwriting >> your existing file (you should probably define another function with >> most of these already fixed for convenience) but should do the trick. > > You can use the information about createFile at: > http://msdn.microsoft.com/en-us/library/windows/desktop/aa363858(v=vs.85).a… > > Regards, > Henk-Jan van Tuyl > > > -- > http://Van.Tuyl.eu/ > http://members.chello.nl/hjgtuyl/tourdemonad.html > -- >

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Real World Haskell: From Portable to System.Win32
by Paulo Pocinho 08 Oct '11

08 Oct '11

Hello Haskellers. I'm having a bit of trouble solving the challenge in chapter 9 of the book Real World Haskell [1]. I understand the portable code and have no difficulty with it. More specifically, I want to know how to get a file's last modified date. Perhaps in understanding this bit I may also extrapolate to similar parts of System.Win32 more easily. A simple example using portable code, and also formats the date: getFileModifiedDate :: FilePath -> IO String getFileModifiedDate f = do m <- getModificationTime f c <- toCalendarTime m return $ formatCalendarTime undefined "%Y-%m-%d %T" c However, the exercise is to "port the code from this chapter to your platform's native API", which in my case is System.Win32. Using the simple example, I know that I can use getFileTime from System.Win32 [2]: getFileTime :: HANDLE -> IO (FILETIME, FILETIME, FILETIME) I suppose that means getFileTime takes a file handle (with type HANDLE) and returns an IO type with CreationTime LastAccessTime LastWriteTime [3]. The thing is I don't know how to get a HANDLE type. I understand I can get a file handle by opening it. I've been trying the following: openFile :: FilePath -> IOMode -> IO Handle fh <- openFile "myfile.hs" ReadMode Right now I cannot use getFileTime on it because this has type Handle: Couldn't match expected type `HANDLE' with actual type `Handle' In the first argument of `getFileTime', namely `fh' In a stmt of an interactive GHCi command: nf <- getFileTime fh I think I got lost at inspecting the type HANDLE = Ptr () If anyone could make a useful example I would appreciate it very much. Perhaps it's just me going around in circles. Regards, P. M. Pocinho -- [1] http://book.realworldhaskell.org/read/io-case-study-a-library-for-searching… [2] http://hackage.haskell.org/packages/archive/Win32/2.2.1.0/doc/html/System-W… [3] http://msdn.microsoft.com/en-us/library/windows/desktop/ms724320%28v=VS.85%…

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sorting
by kolli kolli 08 Oct '11

08 Oct '11

hi, can anyone help me sorting elements of a list ["ala", "zero", "jera"] in alphabetical order

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module not found
by Tyler Hayes 08 Oct '11

08 Oct '11

Hello, Very beginner here. I downloaded the Haskore package with cabal: cabal install haskore but when I import Haskore in my source, I get: Could not find module `Haskore' I've got to be missing something. Thanks, Tyler

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More than one GHC version installed
by Paulo Pocinho 06 Oct '11

06 Oct '11

Hi. I'd like to know if it is possible to have a separate install directory with GHC 7.0.4 and another with GHC 7.2.1 in the same Windows system. I was thinking about having a standard PATH environment "C:\Haskell\ghc\bin". Then have a folder structure like "C:\Haskell\ghc-{7.2.1, 7.0.4}", renaming either one of them into "C:\Haskell\ghc" depending on what I would like to be using. I have taken into consideration to renaming the cabal install directory in the same manner. However, the problem with this approach is that the package database remains somewhere I can't find. Does the default GHC store the package database in the registry or something? I'd appreciate if you could hint me where I could swap the databases for this setup.

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merge two files in to one file
by kolli kolli 06 Oct '11

06 Oct '11

Hi, Can anyone tell me how to merge two files in to one file.

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Peer review of an attempt to solve the golf-tee puzzle?
by Scott Thoman 06 Oct '11

06 Oct '11

Hi, I'm looking to see of anyone is interested in a quick code review. I coded a quick solution to the golf-tee puzzle (like you see a places like Cracker Barrel, 15 piece triangle where you hop the pegs in order to get down to one left). My solution seems to work, seems to perform ok, and seems to come up with a very large number of distinct solutions. I'm looking for some feedback as far as: - am I "getting" it? :) - is the approach general enough? - does it look anything like idiomatic haskell? - any places to make things simpler or more point-free-ish? - any types are overkill, too restrictive (I added the Board type so maybe it could be an instance of Show to display the triangle but didn't go that far) I'll attach the three files here. Thanks in advance for any feedback... /stt

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Re: [Haskell-beginners] [aklug] Re: VPS
by Christopher Howard 04 Oct '11

04 Oct '11

On 10/04/2011 08:36 AM, adam bultman wrote: > What, do I have to *give* you one or something? Because I can, y'know. > > Just so long as you don't spam :) > > On 10/03/2011 06:59 PM, Christopher Howard wrote: >> On 10/03/2011 02:28 PM, adam bultman wrote: >>> Choward, any chance you have a legitimate email somewhere else you could >>> relay through, authenticated-style? >>> >> Legitimate!? My server is legitimate!!! >> >> Assuming you mean a gmail account or such... no. >> >>> You'd accept mail on your dynamic IP, but any outgoing mail sent via >>> your server would be relayed through a third party, via your username >>> and password. It's pretty easy to set up in Postfix, anyway, even with >>> TLS to boot. >>> > heh, heh... thanks, but I actually like the VPS idea better, as I was thinking about getting a cheap one to play around with anyway. Even the cheapest one comes with a static IP, so I could just receive the mail there and forward it on to my personal server, or something like that. As a point of curiosity: with your suggestion, do you rewrite the sender field, or do you send and receive e-mails with different addresses? It seems like a few years ago I remember trying to use a server belonging to one domain to send mail from another domain, and some of the mail was bounced back because the receiving servers detected that the domain in the sender field did not match that of the sending server. @Bruce: Thanks also for the offer, but I think I'll try out a VPS solution. -- frigidcode.com theologia.indicium.us

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LZMA for Haskell?
by Paulo Pocinho 04 Oct '11

04 Oct '11

Hello list. I'd like to use LZMA to create/extract archives and compare CRC from archived files. What do I need to use LZMA in Haskell? There is a page called "Library/Compression" in the wiki [1] but it is from 2005, using LZMA version 4.06. Besides being old, I can only find the LZMA SDK version 9.20 for download. The only related package I can find on hackage is lzma-enumerator [2]. Trying to install with cabal requires an old header named lzma.h that is no longer available. [1] http://www.haskell.org/haskellwiki/Library/Compression [2] http://hackage.haskell.org/package/lzma-enumerator

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