XML DTD for the package configuration file

[Ross Paterson]

On Wed, Oct 15, 2003 at 09:59:41AM -0400, Isaac Jones wrote:
> Or are you agreeing with Daan that we shouldn't be using XML?

I am, and for the same reasons he gave:

> If we describe packages just like ghc-pkg is doing, as a Haskell record,
> we get:
> - very simple code for reading and writing those
> - syntax that is understood by all haskell programmers
> - optional elements (by using records)
> - list elements (by using lists)

I think the second one is the most important, with the flexibility of
Haskell data structures coming second.  There's also brevity, ease of
preparation by humans, simplicity and avoiding reliance on lots of tools.

Note, however, that the package.conf approach is a little more than
Haskell records: the hand-written parsers used by GHC and Hugs allow
omitted fields to be filled in with default values, and the output
function does pretty printing.  (Specs generated by this function or the
derived show can be read with the derived read, though.)  But I think
a little extra code in the library is fine.