How do I create syntactic sugar for Julia functions?

General Usage
6

From reading this thread, I conclude that some symbols are parsed as infix, but some aren’t, for example

julia> function ↑(x, y)
           return x - y + 3
       end
↑ (generic function with 1 method)

julia> 9 ↑ 2
10

julia> function f(x, y)
           return x - y + 3
       end
f (generic function with 1 method)

julia> 9 f 2
ERROR: syntax: extra token "f" after end of expression
Stacktrace:
 [1] top-level scope at REPL[10]:0

Julia parses ↑ as an infix, but not f.

I don’t know if it is possible to make Julia parse f as an infix.