Extending the dependency syntax

[Duncan Coutts]

On Thu, 2005-07-28 at 23:42 +0100, Simon Marlow wrote:

> build-depends:
>     (gconf>=1.0 [gconf] ||)
>     (libglade>=1.0 [libglade] ||)
> 
> But this is starting to get a bit subtle.

Just on a note about syntax. Gentoo uses this syntax for optional
dependencies:

flag? ( dep )

So for example we write the Gtk2Hs build dependencies like this:

DEPEND=">=virtual/ghc-5.04
        >=x11-libs/gtk+-2
        gnome? ( >=gnome-base/libglade-2
                 >=x11-libs/gtksourceview-0.6
                 >=gnome-base/gconf-2 )
        mozilla? ( >=www-client/mozilla-1.4 )
        doc? ( >=dev-haskell/haddock-0.6 )"

Of course cabal doesn't have the complication of package catageories and
such so for a cabal style it'd look more like:

build-depends:
	ghc >= 5.04,
        gnome? ( libglade >= 2,
                 gtksourceview >= 0.6,
                 gconf >= 2 ),
        mozilla? ( mozilla >= 1.4 ),
        doc? ( haddock >= 0.6 )

and also of course these Gtk2Hs deps are actually mostly C libraries.
But you get the idea.

And then we match up these "use" flags (more or less) 1-to-1 with
configure flags that enable/disable optional features.


Just an idea.

Duncan