Re: Libraries Digest, Vol 117, Issue 10

On 10.05.13 9:30 PM, Felipe Almeida Lessa wrote:

IMNSHO, I think we should just add

-- | @whenJust = 'for_'@. Executes the given action -- when @Just@, execute nothing if @Nothing@. whenJust :: Monad m => Maybe a -> (a -> m ()) -> m () whenJust = for_

to Data.Maybe. Even if it's duplicating a functionality, it's a good name that has been reinvented by many people. Its docs may mention for_ and teach the user that for_ is more generic etc. People looking for whenJust *will* look at Data.Maybe. We don't lose much by adding this function.

+1. whenJust seems to be canonical and is reinvented again and again. We can add it now or have the next discussion in 6 month or a year. Previous discussions: June 2009: http://www.haskell.org/pipermail/libraries/2009-June/011836.html Nov 2011: http://haskell.1045720.n5.nabble.com/Proposal-add-Control-Monad-whenJust-Mon... Dec 2012: http://comments.gmane.org/gmane.comp.lang.haskell.libraries/18519 See also Felipe's post at: https://groups.google.com/forum/?fromgroups=#!topic/haskell-cafe/aWtC8DRfGYs Cheers, Andreas

On Fri, May 10, 2013 at 4:00 PM, Gwern Branwen wrote:

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On Fri, May 10, 2013 at 2:54 PM, Chris Seaton wrote:

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Perhaps we should have a dummy module in Hackage that includes commonly searched for functions, but instead of actually implementing them the documentation would say don't use this and suggest an alternative and explains why. Then you could find them in Hoogle and Hackage seems to be highly ranked on Google so they'd be found there as well.

Or expand hlint to catch whenJust like constructs and suggest use of the alternative? We already did that for when 'void' was added, put in a suggestion looking for things like '>> return ()'

-- gwern http://www.gwern.net

-- Andreas Abel <>< Du bist der geliebte Mensch. Theoretical Computer Science, University of Munich Oettingenstr. 67, D-80538 Munich, GERMANY andreas.abel@ifi.lmu.de http://www2.tcs.ifi.lmu.de/~abel/