[Haskell-cafe] real haskell difficulties (at least for me)

Tue Jan 13 12:48:09 EST 2009

Wow, totally ++ this idea!

2009/1/13 Peter Verswyvelen <bugfact at gmail.com>

> What could be done is letting the community rate the quality of the modules
> for each platform? Maybe with user comments? Like amazon.com (so we
> hackazon.org ;-)  And using lambdas instead of stars for giving the rating
> :)
>
>
> On Tue, Jan 13, 2009 at 6:13 PM, Don Stewart <dons at galois.com> wrote:
>
>>
>> Well, the number one thing is to use Cabal and the cabal-install tool.
>> That is the simplest way to avoid headaches.
>>
>> Regarding libraries in general, the platform project is underway, aiming
>> to bless a set of stable, "batteries included" packages, saving
>> duplicated work determining which, say, json library to use.
>>
>> -- Don
>>
>>
>> jamiiecb:
>> > I agree completely. There is not nearly enough documentation on
>> > packaging in haskell and too many hackage packages are broken or do
>> > not install. I know several people are working on improving this but
>> > they seem do be doing so rather quietly. Could someone briefly outline
>> > what improvements are planned and what stage the current work is at? I
>> > remember seeing some demos at anglohaskell during the summer but
>> > nothing since.
>> >
>> > Jamie
>> >
>> > On Tue, Jan 13, 2009 at 3:33 PM, Regis Saint-Paul
>> > <regis.saint-paul at create-net.org> wrote:
>> > > Hi,
>> > >
>> > > I've seen many times the monad topic coming around on the cafe and
>> plentiful
>> > > tutorials on monads have been published. However, as a complete
>> Haskell
>> > > newbie coming from OOP, I felt monads were not particularly difficult
>> to
>> > > grasp, and very exciting to work with.
>> > >
>> > > During my experiments with Haskell so far, the main problems I kept
>> bumping
>> > > into were not related to the language but to its libraries: their
>> > > compilation and installation. Unfortunately, this topic has not
>> received
>> > > nearly as much attention. I was unable to find a comprehensive
>> tutorial on
>> > > how to deal with the variety of problems I get when trying to install
>> > > Hackage packages. This turned out to be (and still is) THE main source
>> of
>> > > wasted time and headaches. And worse, unlike type problems, these are
>> not
>> > > interesting ones to solve.
>> > >
>> > > Thus, as a beginner, the package management is what is really getting
>> in the
>> > > way of switching to Haskell--not the language. Even books like Real
>> World
>> > > Haskell (otherwise excellent) ignore entirely the topic. Cabal and
>> > > Cabal-install are clearly wonderful applications that make installing
>> most
>> > > packages very straightforward. Unfortunately, whenever this "standard"
>> > > method for package installation fails (or when it is not available as
>> with,
>> > > e.g., gtk2hs), I find myself in complete disarray.
>> > >
>> > > Below are some of the questions and issues I faced regarding package
>> > > management:
>> > >
>> > > - For a number of packages, cabal-install gets stuck and has to be
>> killed. I
>> > > assume this is due to some difficulties in solving the dependencies
>> and it
>> > > is fine, not all can be automated and cabal-install is not responsible
>> for
>> > > poor packages. But the question then becomes what to do from there? Is
>> their
>> > > some method to solve dependencies? How should we proceed to "debug" a
>> > > package installation? How do gurus deal with that? (maybe some less
>> known
>> > > command line arguments? Or ways to figure out the problem and work out
>> its
>> > > solution (cabal-install is silent in such case)? In particular, how to
>> know
>> > > why did cabal get stuck in the first place?
>> > >
>> > > - Some packages on Hackage are reported as not building successfully
>> with
>> > > GHC6.10 (e.g., encoding) while others do not build with 6.8 (e.g.,
>> salvia)
>> > > and the later might depend on the former...What is one supposed to do
>> in
>> > > such case? For example, is it an appropriate way to proceed to compile
>> a
>> > > package with one version of GHC and then use the compiled package with
>> > > another version of GHC? Is it safe? What could possibly go wrong? If
>> it is
>> > > the right way to go, how should we setup the two GHC versions? For
>> instance,
>> > > should we have a shared package configuration file and choose through
>> the
>> > > path which GHC is used or is there nicer way to set this up?
>> > >
>> > > - Taking for example the "encoding" package on Hackage. Last time I
>> tried,
>> > > the log was saying it fails to build on GHC 6.10, however, looking
>> inside
>> > > this Hackage log, I could see a successful compilation using
>> "preferred
>> > > versions". So it looks as if the thing can be compiled somehow. What
>> should
>> > > one do with this information? If cabal manages to compile it using
>> this
>> > > method on Hackage, then isn't cabal install just doing it on my disk?
>> Is it
>> > > possible through some command line? Is it possible manually (without
>> > > cabal-install) and, if so, how? (I tried to copy-past the build
>> instruction
>> > > as it appeared on the log...that somehow compiled, but then, I failed
>> to
>> > > figure out how to install...)
>> > >
>> > > - I'm primarily a windows user and lots of my initial struggles
>> probably
>> > > came from that. After many difficulties, I figured out that installing
>> MinGW
>> > > and MSys was *THE* way to get a bit more of the things working. First,
>> a lot
>> > > of time would be saved by just saying clearly on the GHC download page
>> that
>> > > MinGW and MSys are mandatory installation (or even package that with
>> GHC for
>> > > the windows distribution if license allows, who cares the extra few
>> Mb).
>> > > Even if that is not technically exact, i.e., even if ghci and many
>> trivial
>> > > command line programs can work without, MSys and MinGW turn out to be
>> quiet
>> > > necessary whenever trying to install anything producing side effect.
>> Making
>> > > it plain that these two are necessary would real come has a great time
>> > > savers for newbie like me on windows (personal opinion of course). Or,
>> if
>> > > another path exists to go without these two, I'd be very glad to
>> learn.
>> > > Besides, even these tools basic installation is not enough, you need
>> > > automake and various things of the like. That makes me wonder if the
>> most
>> > > precious skill for programming with Haskell would not be a strong
>> C/C++
>> > > programming background.
>> > >
>> > > - In face of the difficulties with windows, I switched to Linux. While
>> some
>> > > things worked better, there were still lots of difficulties with
>> package
>> > > compilation. For instance, it is very difficult to figure out which
>> Linux
>> > > packages of a given distribution are needed for compiling this or that
>> > > package. Again, gtk2hs is epitome here: which C development packages
>> are
>> > > needed to compile it is obscure at best (cairo, codeview, etc...). I
>> ended
>> > > up querying the Debian package management with any keyword found after
>> > > running gtk2hs and randomly installing all the dev packages...And when
>> > > gtk2hs finally compiled, it failed to install anyway. As of today,
>> I've
>> > > never been able to compile even the dumbest demo using gtk2hs whether
>> on
>> > > linux or on windows and whether using ghc 6.8.3 or 6.10.1. On windows,
>> the
>> > > automated setup install worked but did not allow me to compile with
>> codeview
>> > > and I still do not know how to add codeview to the install packages.
>> Trust
>> > > that I tried hard and read the docs thoroughly. Gtk2hs is just on of
>> many
>> > > examples; I had problems under Linux also with, e.g., Happs, yi,
>> database
>> > > things, etc. and figured out that the situation was roughly identical
>> to
>> > > windows with MSys and MinGW. So Linux appears not to be the right
>> solution
>> > > here. Maybe it's just that Linux users are more experienced with the
>> GNU
>> > > C/C++ libraries...but it won't help a windows user to switch to Linux
>> since
>> > > this knowledge can't be built out of thin air.
>> > >
>> > > - Would there be some binary version of cabal targeting various OSs? I
>> > > believe the Haskell platform project is about that. But without
>> waiting for
>> > > a fair and objective selection of the packages (it seems to be the
>> current
>> > > status of the project), I'd be happy working with some authoritative
>> bundle
>> > > produced by a Haskell guru and would trust his subjective choices (who
>> am I
>> > > to question these choices anyway). Or even an image (e.g., virtual box
>> or
>> > > Xen) of a fully setup development environment since there are so many
>> > > dependencies involved in, e.g., simply compiling GHC...
>> > >
>> > > Now, one might argue that these are not Haskell problems, that they
>> are
>> > > normal when dealing with non-mature packages. So let me explain why
>> I've
>> > > been trying hard to install these packages:
>> > >
>> > > As a beginner with no experience with emacs, I tried to find some
>> IDE-like
>> > > environment which would, at least, save me from manually reloading
>> files in
>> > > ghci or help me browse the source files. Following the Haskellwiki
>> advice,
>> > > that led to trying out Yi, Leksah, eclipsefp, or a Visual Studio
>> extension.
>> > > To this date, NOT ANY SINGLE ONE of these worked, be it on Linux or
>> Windows.
>> > > I had to resort to learning emacs which seems the only sensible choice
>> > > available today.
>> > >
>> > > I am particularly unskilled, no question here. But, would a charitable
>> soul
>> > > take the pain of writing a comprehensive package management tutorial
>> instead
>> > > of a monad one, (s)he would have my deepest gratitude :)
>> > >
>> > > Apologies for the long mail.
>> > >
>> > > -Regis
>> > >
>> > > P.S. People on #haskell are wonderful. They helped me solve many
>> issues.
>> > > Unfortunately, solving specific instances of problem did not
>> contribute much
>> > > to a deeper understanding of the internal working. I find myself
>> randomly
>> > > trying things without knowing which would work or why; Hence this plea
>> for a
>> > > tutorial.
>> > >
>> > >
>> > >
>> > > _______________________________________________
>> > > Haskell-Cafe mailing list
>> > > Haskell-Cafe at haskell.org
>> > > http://www.haskell.org/mailman/listinfo/haskell-cafe
>> > >
>> > _______________________________________________
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