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Re: ` fmap (p </>) <$> getDirectoryContents p`

I dunno about mixing infix/prefix when they're both the same function. Lenses tend to guide you towards the fmap.fmap path, as fmap.fmap == traverse.traverse at which point the 'lens' is exactly the same as if you're using it directly, like this.

i.e:
```haskell
over (traverse . traverse) succ
```

```haskell
(traverse . traverse) succ
```

I feel like insisting on binary rules like: the thing to the left is "lifted" into the monadic thing to the right is a little restricting.