Re: [Haskell-cafe] circular dependencies in cabal
Hi Are you still in a "not-able-to-do-a-cabal-install" state? I had this problem as well and I solved it by simply deleting (or moving) my ~/.ghc directory and then re-installing ghc, as per this message: http://markmail.org/message/fraw3cw56squfeld Note: that this should only be used if you can't solve it the suggested way which is to look in your pkg database for packages registered in both user and global databases and unregister the user one. regards allan Valentyn Kamyshenko wrote: So, in practical terms, you suggest that no new version of the package that ghc package depends on (directly or indirectly) should ever be installed? For example, as soon as process-1.0.1.1 is installed on my computer, I'll have this problem with every package that depends on "process"? Another question: would not cabal-install automatically fetch the most recent version of the "process" package, as soon as I will try to install a package that depends on it (such as, for example, "plugins")? -- Valentyn. On Feb 1, 2009, at 6:53 AM, Duncan Coutts wrote: On Sun, 2009-02-01 at 01:33 -0800, Valentyn Kamyshenko wrote: Hello all, when I tried to install plugins package with cabal, I've got the following error: # sudo cabal install plugins --global Resolving dependencies... cabal: dependencies conflict: ghc-6.10.1 requires process ==1.0.1.1 however process-1.0.1.1 was excluded because ghc-6.10.1 requires process ==1.0.1.0 For the most part I refer you to: http://haskell.org/pipermail/haskell-cafe/2009-January/054523.html However the difference is that you've got this problem only within the global package db rather than due to overlap in the global and user package db. It looks like both versions of process package are currently required: It looks like you installed process-1.0.1.1 and then rebuilt almost every other package against it. Of course you cannot rebuild the ghc package but you did rebuild some of its dependencies which is why it now depends on multiple versions of the process package. Generally rebuilding a package without also rebuilding the packages that depend on it is a bit dodgy (it can lead to linker errors or segfaults). Unfortunately cabal-install does not prevent you from shooting yourself in the foot in these circumstances. Any suggestions? Aim for a situation where you only have one version of the various core packages. If you do not need to install packages globally then installing them per-user means you at least cannot break the global packages. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] hmatrix, Windows and GCC
Hi The INSTALL file in the hmatrix repository has some very clear instructions for installation on Windows. http://perception.inf.um.es/~aruiz/darcs/hmatrix/INSTALL However note this section at the bottom: "Unfortunately the lapack dll supplied by the R system does not include zgels_, zgelss_, and zgees_, so the functions depending on them (linearSolveLS, linearSolveSVD, and schur for complex data) will produce a "non supported in this OS" runtime error." Of course linearSolve is exactly what you will be wanting so this won't work for you. I ran into exactly this problem myself. I actually didn't get as far as a run-time error as I got a linker error. I don't have any solution for you though, sorry. regards allan Rafael Gustavo da Cunha Pereira Pinto wrote: Hi all, I am writing a program that uses hmatrix for solving some linear systems. The hmatrix package depends on BLAS, which, in turn, depend on GCC 4.2 to be built (at least ATLAS does). GHC 6.10 for Windows is pre-packaged with GCC 3.4.5, and it leaves me with the impression that I would have incompatible ABIs. My questions: 1) Why GHC 6.10 still uses GCC 3.4.5 in Windows? I know mingw considers GCC 4.2 to be alpha, but, lets face it, 4.2 is almost obsolete! 2) Is it possible to rebuild GHC 6.10, using Windows and GCC 4.2? Is there any guide for doing this? 3) Has any of you tried hmatrix on Windows? How did you do it? Thanks, Rafael -- Rafael Gustavo da Cunha Pereira Pinto Electronic Engineer, MSc. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haddock question [solved]
Ross Paterson wrote: > On Thu, Nov 27, 2008 at 11:52:04AM +0000, allan wrote: >> I'm trying to locally build the documentation for the haskell-src-exts >> package and running into a bit of bother. >> If I run: cabal haddock >> I get the error: >> haddock: parse error in doc string > > The problem is that several of the modules (not Language.Haskell.Exts, > but modules it imports) have headers containing a field "Original" > that haddock doesn't recognize. > a ha, Thank you, that has fixed the problem. regards allan -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] haddock question
Dear all I'm trying to locally build the documentation for the haskell-src-exts package and running into a bit of bother. If I run: cabal haddock I get the error: haddock: parse error in doc string so: cabal haddock -v Doesn't really provide any extra information, it gives me the exact haddock command-line used but there is still no way (I can see) of obtaining the source file containing the parse error. So I downloaded via darcs the latest haddock source code and installed that but I get the exact same error message. I tried grepping in the haddock source code for that particular error message (and portions of it) but I couldn't find it. Finally I tried running haddock on a single source file: haddock Language/Haskell/Exts.hs and even this gets the exact same error message, which is somewhat bizarre since that file does not contain any documentation strings. Anyone have any ideas? regards allan -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Terminal-like Application Design
Hi Jeff
It sounds like maybe you just want an application that works a bit like 'cabal'.
So with cabal the first argument is taken as the 'command' and then the rest
are based on that:
cabal build --some other --options --which may --or --may --not have --arguments
Yi has a simple template for a script which should get you started, please find
it attached.
So here instead of processOptions, you might want, processCommand
processCommand :: [ String ] -> IO ()
processCommand ("build" : args) = processBuildCommand args
processCommand ("play" : args) = processPlayCommand args
processCommand [] = putStrLn "You must supply a command"
processCommand _= putStrLn "Sorry I don't understand your
command" --Probably out put help here as well
processBuildCommand :: [ String ] -> IO ()
processBuildCommand = similar to the processOptions except now you are sure you
are in a 'build' command
you *might* even have a separate set of option descreptions for each command.
hth
allan
Jeff Wheeler wrote:
> Hi,
>
> I'm a slight Haskell newbie, but I'm trying to write a terminal-like
> application that accepts simple commands with optional arguments, and
> can then execute them. Most of these commands will need IO, as later I
> will want to communicate over USB for most of them.
>
> I was hoping, though, that I could get some comments on the initial
> architecture I've been playing with [1].
>
> I suspect I should be using some sort of monad to represent the
> commands, but I don't fully understand monads, and am not sure how it
> would apply in this context.
>
> Should I be using a monad here, and if so, how?
>
> Thanks in advance,
> Jeff Wheeler
>
> [1] http://media.nokrev.com/junk/cli/
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--
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
{-
-}
module Main
( main )
where
{- Standard Library Modules Imported -}
import System.Console.GetOpt
( getOpt
, usageInfo
, ArgOrder( .. )
, OptDescr( .. )
, ArgDescr( .. )
)
import System.Environment
( getArgs
, getProgName
)
{- External Library Modules Imported -}
{- Local Modules Imported -}
{- End of Imports -}
data CliFlag =
CliHelp
| CliVersion
deriving Eq
options :: [ OptDescr CliFlag ]
options =
[ Option "h" [ "help" ]
(NoArg CliHelp)
"Print the help message to standard out and then exit"
, Option "v" [ "version" ]
(NoArg CliVersion)
"Print out the version of this program"
]
helpMessage :: String -> String
helpMessage progName =
usageInfo progName options
versionMessage :: String -> String
versionMessage progName =
progName ++ ": This is version 0.001"
-- | The main exported function
main :: IO ()
main = getArgs >>= processOptions
processOptions :: [ String ] -> IO ()
processOptions cliArgs =
case getOpt Permute options cliArgs of
(flags, args, []) ->
processArgs flags args
(_flags, _args, errors) ->
do progName <- getProgName
ioError $ userError (concat errors ++ helpMessage progName)
-- We assume all of the arguments are files to process
processArgs :: [ CliFlag ] -> [ String ] -> IO ()
processArgs flags files
| elem CliHelp flags= getProgName >>= (putStrLn . helpMessage)
| elem CliVersion flags = getProgName >>= (putStrLn . versionMessage)
| otherwise = mapM_ processFile files
-- Our processing of a file is to simply count the words
-- in the file and output the number as a line.
processFile :: FilePath -> IO ()
processFile file =
do contents <- readFile file
putStrLn (show $ length $ words contents)
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Re: [Haskell-cafe] Libraries in home dir
Hi, In addition if you want to do this all or most of the time, that is there are few/no cabalised libraries you DO wish to install globally, then you can tell 'cabal' to do this all the time by editing your ~/.cabal/config file. Here is mine: repos: hackage.haskell.org:http://hackage.haskell.org/packages/archive cachedir: "/home//.cabal/packages" hackage-username: "" hackage-password: "" compiler: ghc user-install: True user-prefix: "/home//install/" regards allan Dougal Stanton wrote: > On Thu, Oct 9, 2008 at 2:08 PM, Mauricio <[EMAIL PROTECTED]> wrote: >> Hi, >> >> I want to use a few libraries from hackage >> and have already download and built them. Can >> I install those libraries somewhere in my >> home dir (I want to avoid installing as root) >> so that ghc can find them? >> >> If so, which options should I give to Setup.hs >> (with main=defaultMain) so that the libraries >> are going to be copy to that dir? > > Dpeending on whether you have (and are using) cabal-install, either > > $ cabal install diagrams --prefix=$HOME --user > > or > > $ runhaskell Setup.lhs configure --prefix=$HOME --user > > > That will (a) put the libraries etc in $HOME/lib and (b) register > these packages locally. > > Hope that helps! > > > D > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [darcs-users] poll: how can we help you contribute to darcs?
I would contribute to darcs if only It didn't already do exactly what I want it to. As you've said darcs is really good for small-to-medium sized projects, particularly with few developers. Those are exactly the projects I happen to be working on. For my work I use darcs on a slightly larger project but with (mainly) only one developer (me). So basically because darcs works perfectly for me I have pretty little motivation to dive into the source code and 'fix' something which for me simply isn't broken. regards allan Eric Kow wrote: > Dear Haskellers, > > I would like to take an informal poll for the purposes of darcs > recruitment. Could you please complete this sentence for me? > >"I would contribute to darcs if only..." > > The answers I am most interested in hearing go beyond "... I had more > time". For instance, if you are contributing to other Haskell/volunteer > projects, why are you contributing more to them, rather than darcs? > -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem compiling a CGI script that needs to write to file during its execution
Hi
I had this same problem and I'm not sure my way is correct but I used
'Control.Monad.Trans.liftIO'
Here is some code that I am using
{-
The main program is pretty simple we just run the CGI action.
-}
main :: IO ()
main = Cgi.runCGI $ Cgi.handleErrors cgiMain
{-
To be able to produce graphs which we can then display in the output
webpage we require that our main function, that is the one which creates
the page be in the IO monad.
-}
cgiMain :: CGI CGIResult
cgiMain =
do visitInfo <- getAnalysisData
page <- Monad.Trans.liftIO $ createPage visitInfo
Cgi.output $ Xhtml.renderHtml page
createPage :: Visit -> IO Html
createPage . blah stuff you don't care about
getAnalysisData :: CGI Visit
Visit is a data type I've made to hold the information obtained from the page.
Hope this helps
allan
Jefferson Heard wrote:
> Please ignore the obvious security holes, as this is not a script
> meant for public consumption, but some internal testing and
> prototyping. I would like to write the result of my computation out
> to a file inside of cgiMain, but the type of the monad inside cgiMain
> is this odd CGIT IO CGIResult. I tried using liftM on writeFile, but
> it then complained that "newanns" was a string instead of a list of
> strings, which I don't understand at all. Here's the code:
>
> DeleteAnnotation.hs:
>
[snip code]
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Re: [Haskell-cafe] Qualified import syntax badly designed (?)
Neil Mitchell wrote: > Hi > >> Just to say that I also like this design. A minor point would be; do we >> really need the parentheses and commas? or could we not just use >> indentation (I think this about module imports in general). > [snip general agreement] > > However, I think the new syntax for modules, and the new type of > declarations for modules, are separate issues. Sure! > >> Also I wouldn't mind 'as' for the names which are imported which would >> be a bit of a work around for the debate as to whether I should design >> my modules for qualified import or not. Suppose I make a 'NewList' >> module and use the default names then someone could do: >> import Data.NewList >> unqualified map as nlMap >> find as nlFind >> lookup as nlLookup > > I believe old versions of Haskell had this, and it was considered too > confusing. Consider: > > import Prelude unqualified (+) as (-) > > Also people reading the code will find it easier to know N = > Data.NewList (one mapping), than three mappings as you have. > Yes I generally agree there, I don't think 'as' for imported names is particularly important and if it's been tried before and found to be confusing well then that pretty much settles it for me. If I were particularly for it then I'd point out that: import Prelude unqualified (+) as (-) would only be written by someone with limited common sense or someone trying to break things (but I'm sure you could come up with a more realistic example). More importantly for me is the consistency you mentioned, for me it seems inconsistent that you can remap a module name but not an imported identifier. That said, your point about knowing one or three mappings is somewhat compelling and I'm now somewhat less in favour of 'as' for imported names. regards allan -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Qualified import syntax badly designed (?)
Neil Mitchell wrote: > Hi > >> declaration with a regular syntax. For example: >> >> import Data.Map as Map >> unqualified (Map, (\\)) >> qualified (lookup, map, null) >> hiding (filter) > > I think I prefer this to my proposal, plus its closer to the current > syntax. I think its also nearly equal to what Tom Davie came up with, > given some keyword renaming. If we dropped the unqualified keyword, > and just required unqualified things to come directly after, we get > the full benefits of not introducing any keywords. > Just to say that I also like this design. A minor point would be; do we really need the parentheses and commas? or could we not just use indentation (I think this about module imports in general). Also I wouldn't mind 'as' for the names which are imported which would be a bit of a work around for the debate as to whether I should design my modules for qualified import or not. Suppose I make a 'NewList' module and use the default names then someone could do: import Data.NewList unqualified map as nlMap find as nlFind lookup as nlLookup or vice-versa. regards allan -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Precedence and associativity in a pretty-printer
Edsko de Vries wrote: Hi, Is there a nice way to pretty-print such an expression with the minimal number of brackets? I can come up with something, but I'm sure somebody thought hard about this problem before and came up with a really nice solution :) Any hints or pointers would be appreciated, Thanks, You might find Norman Ramsey's paper on unparsing helpful: http://citeseer.ist.psu.edu/194913.html or google for Norman Ramsey Unparsing regards allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Data.Binary and serialising doubles in IEEE format
Dear all I have what I think should be a relatively simple problem: I have a C program which reads in data from a binary file, it is a specific format so it knows that there are 3 integers followed by three doubles or whatever. So I'm trying to serialise the data from within a Haskell program and write it out to a file such that the C program can read this. I've gotten the integers to work no problem but I'm having difficulty with the doubles. My method is to use the Data.Binary library to write the data out as a bytestring and then simply write this out to disk. The problem is that the instance of Binary for Double does not serialise the data in the format which is expected by the C program (standard IEEE format using fread and a cast). Now there was a thread on (essentially) this very same topic on haskell-cafe back in April, see: http://www.haskell.org/pipermail/haskell-cafe/2007-April/024596.html There was some discussion about the 'right' thing to do and that the library intended to be split into two separate portions; one for users that wish to serialise their own data and have it readable by the same haskell program, and those that wish to communicate with programs written in other languages. From the above thread: Perhaps we just don't care about ARM or other arches where GHC runs that do not use IEEE formats, I don't know. If that were the case we'd say something like: instance Binary Double where put d = assert (isIEEE (undefined :: Double)) $ do write (poke d) Now for my specific problem I'd be happy if I could write a function: putDouble :: Double -> Put and so obviously I tried: putDouble :: Double -> Put putDouble d = assert (isIEEE (undefined :: Double)) $ do write (poke d) However I seem to be stuck at this point, where does the 'write' function come from? Essentially then, is there anyone that can write my 'putDouble' function or give some hint as to how I might do it. For the moment assume that I'm not really concerned with portability across platforms at least for the time being (I certainly don't think that the C program I'm attempting to communicate with is particularly portable anyway). kind regards allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Am I blind?
I've searched all over the place, and I can't find this information actually "announced" anywhere except on the GHC homepage itself. And yet, I've seen emails bouncing around that appear to be replies to the announcement email. But I can't find the actual announcement email anywhere. Am I going mad? It was on just the Haskell rather than Haskell-cafe mailing list. http://www.mail-archive.com/[EMAIL PROTECTED]/msg20759.html regards allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Call external program and get stdout
Roberto Zunino wrote: Allan Clark wrote: -- Create the process do (_pIn, pOut, pErr, handle) <- runInteractiveCommand command -- Wait for the process to finish and store its exit code exitCode <- waitForProcess handle Warning: this will get stuck if the command output is so big that it fills the SO buffers. This limit is 64K here. Regards, Zun. Ah thanks for the warning, I've never tested this on anything particularly large. regards allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Call external program and get stdout
Jules Bean wrote:
Maurício wrote:
Hi,
How can I call a program (like, for instance,
'grep text *') and get the standard output?
All actions I found (executeFile, system) do
not give me the output of the program.
http://haskell.org/ghc/docs/latest/html/libraries/process-1.0.0.0/System-Process.html
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I was using the following:
{-
A small function for blindly running a process until it completes
its output and then waiting for its exit code.
We return both the output (excluding stderr) plus the exit code.
-}
getProcessOutput :: String -> IO (String, ExitCode)
getProcessOutput command =
-- Create the process
do (_pIn, pOut, pErr, handle) <- runInteractiveCommand command
-- Wait for the process to finish and store its exit code
exitCode <- waitForProcess handle
-- Get the standard output.
output <- hGetContents pOut
-- return both the output and the exit code.
return (output, exitCode)
You'll need the following imports:
import System.IO
( hGetContents )
import System.Process
( runInteractiveCommand
, waitForProcess
)
import System.Exit
( ExitCode ( .. ) )
regards
allan
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Re: [Haskell-cafe] Yi pre-release
Patches, comments, criticism welcome... as always! -- Jean-Philippe Bernardy I have a question, my compilation gets stuck on configure, it can't find package FilePath >=1.0 Which file path library is this? There are a few around, but I can't seem to find one with a version number greater than or equal to 1.0. regards allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How you can help improve Haskell implementations!
Donald Bruce Stewart wrote: Just a quick note to say that the Haskell implementation shootout is progressing, now supporting jhc, fixing a range of bugs, and providing more benchmark programs. Nice average numbers are also reported for the relative performance of each compiler or interpreter. On x86: http://www.cse.unsw.edu.au/~dons/nobench/i686/results.html On amd64: http://www.cse.unsw.edu.au/~dons/nobench/x86_64/results.html Several bugs in our beloved Haskell compilers have been spotted, and most of them already fixed! And also I guess the compilers will do more optimisations, etc. So this suggests an obvious extra feature for nobench which would be the ability to view a graph of each compiler's performance over a period of time, obviously this probably wouldn't be useful for at least a few months. However in particular it would be very good for the compiler writers to be aware if the performance goes *down* that is a further release of a compiler causes a benchmarked program to run slower. regards allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Is lazyness make big difference?
i.e. to use Monad.Writer in stead of Monad.State. The point is that for example 'typedProgram' does not really depend on the contents of 'log', but the dependencies in your code don't express this. One should switch from Log -> (a, Log) to (a, Log -> Log) or even (a, Log) if Log already has a natural monoid structure. Yes of course you're quite right, in general I would have the last version ie (a, Log). I did not wish to muddy the example, but probably it was not helpful to have 'typedProgram' depend on the contents of 'log'. regards allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is lazyness make big difference?
Nick wrote: Hi all, (Another topic stolen from a Russian forum discussion). As everyone know, there are lot of strict languages, that have possibilities to "switch on" lazy evaluation when needed. But the examples that I saw on Haskell, there was not much use of lazy evaluation, often there were just several lazy points, and the rest could be done strictly without loss of generality. For example, in finding primes: I think the Haskell solution is more compact due to syntactic sugar, curring and "parentheses-free-ness", *not* lazy evaluation. Hi, I think a big advantage is that programs can be written without regard for whether or not a value will in the long run actually be evaluated. For me one of the best examples of this is that of logging within a compiler. Consider a compiler which operates roughly as such compileProgram :: String -> IO () compileProgram program = let (log, abstract) = parse program (log2, typedProgram) = typeCheck abstract log2 (log3, convertedProgram) = convertToIntermediate typedProgram log2 (log4, convertedToAssembly) = convertToAssembly convertedProgram log3 in do writeFile "a.asm" (show convertedToAssembly) writeFile "a.log" (show log4) Now each of the intermediate transforming calls will produce some logging information which is added to the current log. Some of these will require quite heavy traversing of the entire program, which will almost certainly require auxiliary functions. Suppose we want to allow the suppressing of the log information ie: compileProgram :: String -> Bool -> IO () compileProgram program logOrNot = let (log, abstract) = parse program (log2, typedProgram) = typeCheck abstract log2 (log3, convertedProgram) = convertToIntermediate typedProgram log2 (log4, convertedToAssembly) = convertToAssembly convertedProgram log3 in do writeFile "a.asm" (show convertedToAssembly) if logOrNot then writeFile "a.log" (show log4) else return () Now if this is a strict language we have to go and modify all the intermediate functions to first of all take in a boolean and then use that to decide whether or not to produce any logging information. With a lazy language though, we don't need to do that, we're already done, no logging information will be produced if 'logOrNot' is false, because it will never be forced to evaluate the thunk. According to one guy's analogy: the Real World is strict - in order to drink tea, you have to put the cattle on the fire, wait until water boils, brew tea and then drink. Not the cattle is put on the fire, water boils and the tea is brewed when you take the empty cup to start drinking. :-) Yes true, but you don't just boil up the kettle and brew the tea unless you have first asked if anyone actually wants tea. The question is the following: how big the gap between strict languages with lazy constructs and Haskell? Does the default lazyness have irrefutable advantage over default strictness? Thank you for the attention. With best regards, Nick. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Command line prompt templates
Dougal Stanton wrote: I was trying to write my own equivalent to Don Stewart's mkcabal but ended up getting sidetracked. I made some generalised prompts for use at the command line and wanted to get some feedback on them. The full code can be found at [1] but the basic summary is like this: Hi, I also have a small module for use in a project I'm writing which I use for command line 'asking', you can find the code at : http://homepages.inf.ed.ac.uk/s9810217/software/fragments/Hask.hs and I guess it's possible something there might be of use to you. regards allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal in ghc 6.4.2
Yes, Char is in the haskell98 package, the new name for Char is Data.Char which exports a bit more. Either add haskell98 as a package, or replace Char with Data.Char (which is in base), I'd recommend the latter, but either should work. Thanks Neil a ha, that works, thank you both very much, I can sleep easy now. allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal in ghc 6.4.2
The Text.ParserCombinators.Parsec modules are in the parsec module. build-depends: base Add parsec here: build-depends: base, parsec The reason it works when you run it without -hide-all-packages is that by default for convenience all packages are 'exposed'. That is they can be used without explicitly having to specify them. However it was felt that for distributing software, which is one of the main purposes of Cabal, one should be fully explicit about the dependencies so that users compiling on other machines know exactly what packages needed and don't end up with mysterious import errors. Yip this sounds like a good policy to me too. Now it's true that Cabal could be a bit cleverer here and warn you before it even starts compiling that you have not specified all the right packages in the build-depends. At the moment however Cabal doesn't have a proper imports chaser so it can't do this. Duncan Thanks very much for the response, however, adding "parsec" to the build-depends of the .cabal file now causes a slightly different error, and in fact this is the same error I get with my other project: haskellprint$ ./Setup.hs build Preprocessing executables for haskellprint-0.1... Building haskellprint-0.1... Chasing modules from: Main.hs Could not find module `Char': use -v to see a list of the files searched for (imported from ./Parser.hs) haskellprint$ so basically I was expecting 'Char' to be in the 'base' package, I guess this is wrong? thanks again. allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Cabal in ghc 6.4.2
Hello all, (before I start I should say I'm relatively new (a few months) to haskell, so I'm not exactly savvy with the use of the compilers) I have a problem using the cabal with version 6.4.2 of ghc, the same thing occurs with two projects which I wish to compile, I'll use the simplest one since the problem seems to be the same in both cases. The program is a very simple printer thing for haskell the source of which you can download at: http://homepages.inf.ed.ac.uk/s9810217/software/haskell_print/haskellprint.tar.gz <http://homepages.inf.ed.ac.uk/s9810217/software/haskell_print/haskell_print.tar.gz> (but you probably won't need to, in order to diagnose this problem) I wish to compile this with the sequence of commands: ./Setup.hs configure --user --prefix=/home/allan/install ./Setup.hs build this works perfectly on version 6.4 of ghc, however with version 6.4.2 I get the following error: haskellprint$ ./Setup.hs build Preprocessing executables for haskellprint-0.1... Building haskellprint-0.1... Chasing modules from: Main.hs Could not find module `Text.ParserCombinators.Parsec': use -v to see a list of the files searched for (imported from ./Parser.hs) haskellprint$ Now if I run haskellprint$ ./Setup.hs build --verbose then I can see the command line used to compile the program which is: /home/allan/install/bin/ghc -Idist/build -o dist/build/haskell_print/haskell_print --make -Wall -hide-all-packages -i -idist/build/autogen -i. -odir dist/build/haskell_print/haskell_print-tmp -hidir dist/build/haskell_print/haskell_print-tmp -package base-1.0 Main.hs If I copy and paste this into the command line and remove the argument [ -hide-all-packages ] then the program compiles fine. So basically my question is: what am I doing wrong? I assume my problem is in the .cabal file, so I include the contents here: name: haskellprint version:0.1 license:GPL license-file: LICENSE author: Allan Clark maintainer: [EMAIL PROTECTED] build-depends: base executable: haskell_print main-is:Main.hs include-dirs: c-sources: other-modules: extra-libraries: extensions: ghc-options:-Wall -- ghc-options: -fwarn-incomplete-patterns -fwarn-missing-fields -- ghc-options:-prof -auto-all -Wall -fglasgow-exts -O -funbox-strict-fields -fasm -optl-Wl,-s thanks in advance for any help. allan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
