I think the easiest way to explain point-free is this bash snippet:
grok () {
grep -v DEBUG | sort -n | uniq | tail
}
Unlike a generic pure function, it forcibly abstracts away arguments. It's a bunch of other functions combined somehow, but it's impossible to know the type/structure/semantics of the input. And in most cases also of the output! Although it's less visible in my example.
Of course it’s possible. Just look at the type signature of each function to know what goes in and what comes out. Not much different then looking at the type signature of an assigned variable.
Debugging the point free style is different though as there are no points to put your breakpoint. Think of the identity function with a side effect as a replacement for print or breakpoints.
