version tags

[Duncan Coutts]

On Fri, 2008-05-09 at 10:29 +0100, Ross Paterson wrote:
> On Fri, May 09, 2008 at 10:12:06AM +0100, Duncan Coutts wrote:
> > It's clear we should drop the check on the tags from the == test but I'm
> > not sure if we should also change the showVersion or parseVersion
> > functions.
> > 
> > I'm planning on changing the equivalent of showVersion in Cabal to not
> > display the tags.
> 
> What are tags for? 

>From the code in base:

 versionTags :: [String]  -- really a bag
    -- ^ A version can be tagged with an arbitrary list of strings.
    -- The interpretation of the list of tags is entirely dependent
    -- on the entity that this version applies to.

> Should we have them at all?

Getting rid of them is a bit harder because it's a data type defined in
the base library.

> Currently they've been used in:
> 
> 	hsgnutls-0.2.3-barracuda
> 	hsgnutls-0.2.3.1-barracuda
> 	regex-tdfa-0.92-ghc-68-build-fix
> 
> which seem to be non-maintainer releases.  You'd want such versions to
> be distinguished from the untagged versions.

Perhaps so, but are tags the right way to do it?

If we take them into account for equality then we have to do so for
ordering too. We'd have to do something like comparing the sorted lists
of tags. 

If we keep them I'd prefer to just carry the info around but ignore it.

If we wanted to support tags we'd have to do it consistently all the way
through. They do not translate into distro packages which is a great
disadvantage imho.

Duncan