Comment by jcparkyn

This applies everywhere, and it fundamentally wouldn't be possible for just function calls.

> needless cost

Are you comparing to a language with mutable references or a our functional language? A language with mutable references will of course be faster, but this is more intended as an alternative to pure functional languages (since functions are referentially transparent).

In this case, the cost of the indirection is approximately zero (relative to the cost of just doing reference counting), since passing a reference just requires a bump to the refcount. And most of the time the refcount increments are skipped by "moving" instead of copying the reference.