[Haskell-cafe] A very nontrivial parser

[Jonathan Cast]

On Sunday 08 July 2007, Andrew Coppin wrote:
> Jonathan Cast wrote:
> > I think surely you're using existential data types rather than rank-2
> > types.
>
> You expect *me* to know?

Surely not :)  That's why I tried briefly explaining the ideas again.

> > Existential types: each application of Encoder2 is to arguments which
> > require a specific value of x.
> >
> > Rank-2 types (polymorphic fields, actually): each application of Encoder2
> > is to arguments which work with any value of x.
>
> All I know is it didn't compile, so I added {-# LANGUAGE Rank2Types #-},
> and now it works. *shrugs*

If  you're happy, then I guess I can accept the situation.  I think you'll 
trip over the distinction again, but that's just me.

Jonathan Cast
http://sourceforge.net/projects/fid-core
http://sourceforge.net/projects/fid-emacs