[Haskell-cafe] OS Abstraction module??

[Galchin Vasili]

Hi Ryan,

    Thanks for your generous response. " By the way, you don't want to use
typeclasses here; they solve the
problem of having more than one possible interface at runtime, whereas
you only care about compile-time" .. in reality I do care about decisions
made at run-time (this just struck me as I am writing).  I am trying to
avoid "ifdef's" and have all decisions made at run-time (maybe given the
nature of Haskell .. i..e static/compile-time type checking this is
impossible) ... Trust me as i said in a previous post I am not a big fan of
C++. I guess we are talking about strong type checking .. but static vs
dynamic .. in the case of C++ it is a mixture, e.g. when a C++ class's
member function is not "virtual" then "call resolution" is done at
compile-time vs "virtual" when it is done at run-time via the virtual
function table. Everybody ... by no means am I a booster of C++ .. i.e.
"done it, seen it ...". Maybe a previous "poster" addressed my concerns. In
discussing this OS Abstraction Layer, I think I am thinking of some notion
of "laziness" (read ... decisions made at run-time .. not compile-time ..
otherwise I think we have to resort to ifdefs which are not so nice and
require a lot of code maintenance.)

Kind regards, Bill

On 10/22/07, Ryan Ingram <ryani.spam at gmail.com> wrote:
>
> Also, note that it's really easy to hide all the CPP uglyness in a
> single file, or do it with Makefiles, or something along those lines.
>
> By the way, you don't want to use typeclasses here; they solve the
> problem of having more than one possible interface at runtime, whereas
> you only care about compile-time.  The easiest way to solve that
> problem is through the module system.  An example follows.
>
> with this directory tree:
> System/Abstraction.hs
> System/Abstraction/POSIX.hs
> System/Abstraction/Windows.hs
>
> in System/Abstraction.hs:
>
> module System.Abstraction (
> #if POSIX
>     module System.Abstraction.POSIX
> #elsif WINDOWS
>     module System.Abstraction.Windows
> #endif
> ) where
>
> #if POSIX
> import System.Abstraction.POSIX
> #elsif WINDOWS
> import System.Abstraction.Windows
> #else
> #error Unknown system type
> #endif
>
> Now you can write POSIX.hs and Windows.hs independently to implement
> whatever OS/foreign interface you care about, and your other code can
> import System.Abstraction without needing -cpp.
>
> Alternatively you can make POSIX.hs and Windows.hs just declare
> themselves as "module System.Abstraction" and use your build system to
> compile the correct one.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20071022/f415838b/attachment-0001.htm