Applicative style for infix operators?

Question

Is there a way to make applicative uses of <$> and <*> look nice when dealing with infix operators? I think that

((++) <$> a <*> ((++) <$> b <*> c ))

looks much more cluttered then

a ++ b ++ c

so I wonder if there is a nicer way.

If they are all the same operator, you could use `foldr1 (liftA2 (++)) [a, b, c]`. — Ptharien's Flame, Oct 02 '12 at 02:45

score 12 · Accepted Answer · answered Oct 02 '12 at 02:44

12

(<++>) = liftA2 (++)
a <++> b <++> c

or

liftA2 (++) a $ liftA2 (++) b c

answered Oct 02 '12 at 02:44

singpolyma

score 6 · Answer 2 · answered Oct 02 '12 at 06:19

6

See Thomas Davie's InfixApplicative package, which provides a general syntactic trick, rather than having to define a new operator for each lifting.

answered Oct 02 '12 at 06:19

Conal

2

The documentation is a bit mangled. I *think* the OP's example would translate as `a <^(++)^> (b <^(++)^> c)` --- can you confirm/deny? – dave4420 Oct 02 '12 at 09:04

score 3 · Answer 3 · answered Oct 02 '12 at 07:46

3

SHE lets you write

(|a ++ (|b ++ c|)|)

if that's any use. Of course, there's some overhead to introducing a preprocessing layer.

answered Oct 02 '12 at 07:46

pigworker

3 Answers3