Proposal: add liftA4 and liftA5 to match liftM4 and liftM5

[Henning Thielemann]

On Thu, 6 Nov 2014, Eric Mertens wrote:

> For what it's worth, the liftA_ versions are suitable for partial application. Additionally I tend to prefer
> liftA2 to reimplementing it each time with <$> and <*> in the same way that I prefer sum to foldl' (+) 0,
> liftA2 expresses my intent while f <$> x <*> y feels leaky. That's not to say I never use it, but the
> operators certainly don't obviate the need for the liftA_ combinators.

I think I use liftM* and liftA* much more than <*>. They are really more 
handy for partial application. Thus I would welcome liftA4 and liftA5.


Btw. I also avoid to use <$> together with <*>, but prefer

    pure f <*> a <*> b <*> c

because then every argument is matched with a <*>.