The lens library defines (<&>) with very low precedence (1), whereas (<$>) has precedence 4. If you define (<&>) yourself and specify a precedence higher than 4, or just don’t specify a precedence at all, your example will work fine:

(<&>) :: Functor f => f a -> (a -> b) -> f b

(<&>) = flip fmap

"foo" <**> "bar" <&> (,)

You can do hanging style too, with no dollar sign:

"foo" <**> "bar" <&> \q r ->

..(q, r)

If you don’t like defining ad-hoc versions of things like (<&>), you might find the ‘overhang’ library useful: https://hackage.haskell.org/package/overhang-1.0.0/docs/Overhang.html#v:onMap

The overhang equivalent of (<&>) is ‘onMap’ and it can be used in the same way:

import Overhang (onMap)

"foo" <**> "bar" `onMap` (,)

The code aesthetics around writing a “final" lambda that spans several lines was the driver for creating that library!

Jason

On Feb 6, 2018, at 12:37 PM, Neil Mayhew <neil_mayhew@users.sourceforge.net> wrote:

On 2018-02-06 07:59 AM, MarLinn wrote:
I've been bitten multiple times because of my own invented operators. What was (>>?!) again? Or (^>>>&)? The more I use Haskell the more I tend to solutions like that first dead-simple one.

I agree.

Also, since

func <$> "foo" <*> "bar"

is the lifted equivalent of

func "foo" "bar"

I find it unintuitive to read or write the logic in the opposite order.

Whether we like it or not, Haskell is fundamentally a right-to-left language. Or, to look at it another way, top-down corresponds to left-to-right, and bottom-up corresponds to right-to-left. Perhaps it depends on whether you're a top-down thinker (like me) or a bottom-up thinker. I much prefer `where` to `let`, for example.
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