So the language has reference semantics, and (per the edit) for every object (like in Python)?
(Ah, no, your example elsewhere in the thread suggests that the referred-to structures get implicitly copied all over the place.)
(Ah, no, your example elsewhere in the thread suggests that the referred-to structures get implicitly copied all over the place.)
Optimization specifically for function calls, or... ?
Because if you're doing all this copy-on-write anyway, the indirection seems to be a needless cost in other contexts.
> 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.
But I think at this point I'd have to read and analyze the code to have a proper understanding.
... Although granting that you already have paid the cost of reference-counting GC (and, I assume, per-object allocation), it probably is indeed insignificant. And special-casing where the reference count == 1 is also kinda neat. (E.g. CPython doesn't "move references" per se if I'm thinking clearly; but it does detect cases where it can safely mutate the underlying implementation of a type that's "immutable" from the perspective of language syntax.)