Re: bind :: Monad m => (a -> m b) -> m a -> m b

11 Dec 2014

      Many people seem to be suggesting that this isn't a useful function to
have, but I just found myself wanting it for a pattern that I write a
lot. The code in question is: 

  traverse
        (\s ->
           case s of
             Sector{..} ->
               liftIO (do sectorDrawWalls
                          sectorDrawFloor
                          sectorDrawCeiling))
        =<< view sectors

That is, I want to traverse some sort of structure, and the structure
that I want to traverse itself comes from performing a monadic
action. Imo, this would be more readable as

  bind (traverse (\s ->
                    case s of
                      Sector{..} ->
                        liftIO (do sectorDrawWalls
                                   sectorDrawFloor
                                   sectorDrawCeiling)))
       (view sectors)

Whatever we call it, I do feel it has use -- `traverse f =<< m` comes up
a lot, but with a complex f, using =<< or >>= leads to less
readability. Maybe I spend too much time with Chris. ;) 

-- ocharles

Re: bind :: Monad m => (a -> m b) -> m a -> m b

Oliver Charles