[Haskell-cafe] Hoogle works once more

Neil Mitchell ndmitchell at gmail.com
Thu Dec 6 12:22:31 EST 2007

Hi Dennis,

> Not sure if this qualifies in any category above, but I just searched for:
>     Monad m => m (m a) -> m a
> And I couldn't find Control.Monad.join on any of the first 4 pages or
> so of results.  If I search for join, of course, the first result is:
>     Control.Monad.      join    :: Monad m => m (m a) -> m a
> Is this a bug, or simply a known limitation?  If the latter, is there
> a workaround, in case I happen not to know the name of join?

Unfortunately its a known bug, and there are no workarounds. Removing
the Monad m => part of the query will actually make it more likely to
give back join, but is still not great. The problem is that when I
wrote Hoogle 3 I didn't understand higher-kinded type classes, and as
a result, Hoogle 3 does a particularly bad job on them. The next
version has been designed from the beginning to handle them properly,
so once that's finished, you'll have no more problems.



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