generalization of maybeToList

Edward Kmett ekmett at
Wed Feb 15 16:59:47 CET 2012

On Tue, Feb 14, 2012 at 8:03 PM, Jeff Shaw <shawjef3 at> wrote:

> If we want to argue about maybeTo and the Fairbairn threshold, probably we
> should argue about whether to include maybeToList, which is less general
> than maybeTo.

This is a much harder sell, because it has to overcome the fact that such a
change for the sake of intellectual purity would break existing code

The fact that this becomes a consideration is further argument against
carelessly expanding the library.

I'm not saying that the combinators under discussion are a careless
expansion, merely that their addition needs to be weighed against those
other concerns.

I'm still a lukewarm +1 for adding maybeTo/maybeA if better names can be
derived. Annoyingly it doesn't fit any of the m prefix or M suffix
guidelines in Control.Monad, so the obvious maybeM or mmaybe would be

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