Yeah, that's pretty unclean on two aspects: breaks pairs, and breaks the orthogonality of s-expressions
A simple macro would've sufficed, say:
(compose
sum
(numbers 1 2 3))and beside multiple-args, there's the usual threading macros
(-> [1 2 3] f g)
I don't think it's too bad orthogonality wise, though it is a bit weird to introduce infix notation. It would almost make more sense to write
((. sum numbers) (1 2 3))