On Tuesday 19 February 2008 09:22:34 am Christian Maeder wrote:
Duncan Coutts wrote:
On Tue, 2008-02-19 at 12:01 +0100, Henning Thielemann wrote:
On Tue, 19 Feb 2008, Christian Maeder wrote:
In order to avoid several #ifdefs (maybe differently or suboptimal given) in user sources (to achieve 1.) such #ifdefs (or wrappers) should be part of the libraries (including the documentation for the license differences)!
Can Cabal-1.2's flag capability manage such a task?
I don't think I understand the problem clearly enough to say. Perhaps someone can try explaining it in more detail.
Currently, we have packages Shellac-readline and Shellac-editline. with
exposed-modules: System.Console.Shell.Backend.Readline
resp.
exposed-modules: System.Console.Shell.Backend.Editline
Each module exports a single constant:
Prelude> :browse System.Console.Shell.Backend.Editline editlineBackend :: System.Console.Shell.Backend.ShellBackend () Prelude> :browse System.Console.Shell.Backend.Readline readlineBackend :: System.Console.Shell.Backend.ShellBackend ()
On Macs I want to use Editline, under Linux Readline, Therefore I #ifdef my sources. (The functionality seems to be the same for both packages)
My questions are:
1. Should not the exported constants have the same name 2. Should not even the module name be the same in both packages
I don't think so. I personally view such "top level" overloading as undesirable. There might possibly be a legitimate reason to want both modules avaliable simultaneously. Punning the module name would make that impossible. If you want a package that multiplexes the editline package or the readline package depending on avaliability, that would be easy to do. It would just require wraping up the #ifdef stuff needed into a single place. I can probably find a few minutes this afternoon/evening to do this.
As long as not both packages are installed the compiler would pick the proper package without my #ifdefs.
HTH Christian