On 26 Aug 2010, at 08:01, michael rice wrote:
Hmm... it was my understanding that the example was showing how to *avoid* having to create a lot of functions that do the same thing but have different numbers of arguments.
From the Wiki page:
"Anytime you feel the need to define different higher order functions to accommodate for function-arguments with a different number of arguments, think about how defining a proper instance of Applicative can make your life easier."
Not so?
Very much so – instead of defining liftA2, liftA3 etc like this, just use pure to get things into the applicative, and write <*> instead of ' ' to apply applicatives and you're done. Don't write liftA3 sumsq (Just 3) (Just 4) (Just 5) Write (pure sumsq) <*> (pure 3) <*> (pure 4) <*> (pure 5) or you can get rid of that first pure with a quick fmap: sumsq <$> (pure 3) <*> (pure 4) <*> (pure 5) Bob