[Haskell-cafe] postmortem question about xmonad

Jason Dagit dagit at codersbase.com
Tue Sep 30 18:14:54 EDT 2008

On Tue, Sep 30, 2008 at 1:20 PM, Don Stewart <dons at galois.com> wrote:

> noteed:
> > Hi,
> >
> > I'd like to know, now that time got by a bit, what the writers of the
> > X monad think about the use of the ReaderT/WriterT/IO brought to them
> > (to isolate Configuration data and dynamic data and glue them together
> > with IO). Are you happy of it, did it make things easier or not, would
> > you do it again ?
> It made the structuring and invariants between runtime data, and
> configuration data clean and precise. Yes, A+++ would buy again.

I can add to this, saying that I used WriterT/ReaderT and Unique in a
CodeGen monad I created for a compiler I'm writing and this approach of
stacking monads (well, really transformers) works amazingly well.  Many of
the existing monads abstractly handle a particular task very well.  When you
combine this with generalized newtype deriving it's not just code reuse,
it's also code specialization.  You quickly glue together existing
functionality that works but expose it with the API that meets your problem
domain.  I'd say this is not unlike the way people glue together unix tools
on the command line.  This is RAD in Haskell.

I agree with Don, I would buy this again.  In fact, I've already placed an
order for use in future projects.

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