[Haskell-cafe] SYB: queries using IO Monad

JP Moresmau jpmoresmau at gmail.com
Fri Nov 1 10:07:28 UTC 2013

You're perfectly right Andres. ext1Q and extQ work well with monadic result
type. I can't get gmapQ to work though, but I seem to in fact not need it,
so I've removed its usage totally.

Thanks a million!


On Fri, Nov 1, 2013 at 10:00 AM, Andres Löh <andres at well-typed.com> wrote:

> Hi.
> > However, the ext1Q, extQ and gmapQ functions have no monadic equivalent.
> > There seems to be monadic transformation (from a to different a) but no
> > monadic queries (from a to b).
> > Do I have to rewrite these functions myself to work with monadic queries
> (it
> > at all possible) or is there a better way? I've seen some functions that
> > work with monads and MonadPlus, but I don't see anything that would work
> > with IO.
> I think the idea is that the Q functions don't need a monadic
> counterpart because they can already be used at a monadic result type.
> Cheers,
>   Andres
> --
> Andres Löh, Haskell Consultant
> Well-Typed LLP, http://www.well-typed.com

JP Moresmau
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