Nope, it can only call other side-effect free things. Note however if you call a procedure from a function the function will try to see if the proc is actually

Nope, it can only call other side-effect free things. Note however if you call a procedure from a function the function will try to see if the proc is actually side effect free, just not marked as such. So you can still call a proc, but only if it could've been a func.