[Haskell-cafe] Re: I/O interface

[Andre Pang]

On 20/01/2005, at 11:06 PM, Keean Schupke wrote:

> I find it no harder than writing with monads for example... certainly 
> there are some
> tricky things going on in both... but that doesn't stop people using 
> monads for IO,
> state etc.
>
> Syntactic sugar over the top for instance and implementation 
> definitions is something
> we are working on (using template-haskell) - so that end of things can 
> certainly be
> made neater for the user.

The syntactic sugar is the killer.  (Using monads is really no fun if 
you don't have do notation, for example.  Doable: yes.  Pretty: 
definitely not!)  Even if you use Template Haskell to try to implement 
the syntactic sugar, you're very limited by the splice $(...) notation 
at the call site.  I've always argued that Haskell really should have a 
full-blown macro system: it would really help with Haskell and EDSLs, 
and of course for integrating these kinds of libraries.  TH is 90% of 
the way there, and with a bit more thought, those pesky splices could 
just magically disappear ... ;)

> The big problem I guess is error messages - and that would require 
> some user
> defined way of throwing compile time errors.

Yes, also agreed.  I did some similar Haskell<->OO integration work, 
and the type errors which appeared when something went wrong are quite 
awesome.  User-defined compile-time errors would be fantastic, but that 
would require quite a lot of effort.


-- 
% Andre Pang : trust.in.love.to.save  <http://www.algorithm.com.au/>