[Haskell-cafe] Re: what about moving the record system to an addendum?

John Meacham john at repetae.net
Tue Jul 7 17:33:57 EDT 2009

On Tue, Jul 07, 2009 at 10:28:11AM -0400, Ravi Nanavati wrote:
> 2. Once deprecated, people will be encouraged to not depend on the
> traditional record syntax where the cost of avoiding it is small (I'm
> thinking of situations like the mtl-accessors / run functions where
> the traditional syntax is saving something like one function
> definition).
> 3. Champions of alternative record syntaxes will know what on Hackage
> they can use out-of-the-box and what things they'd want to consider
> re-writing as examples of how their approach is superior.

Well, that's the problem. I don't want to ever deprecate the named field
mechanism as it is completely independent of a record system. You can
think of the possibilites as follows.

            named             positional

declared   LabeledFields      DataDeclarations

anonymous  ????               Tuples

So, a record syntax fills the hole of anonymous, named field types.
However, we shouldn't do it at the expense of opening another hole with
declared, named field types any more than we should dispose of standard
data declations in favor of making everything newtypes of tuples.

Also, this supports the idea of using parethensis rather than braces for
a record mechanism. this would be consistent with tuples in that parens
= anonymous. Also, if you just replace braces with parens in the scoped
records paper, you get no conflicts with existing syntax. (including
named fields) :)


John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/

More information about the Haskell-Cafe mailing list