Any idea why it&#x27;s no longer in use? The memory argument against vtables seems spurious - I&#x27;m using vtables everywhere for my in-progress Ruby compiler (with the intent of allowing an arbitrary cut-off on the vtables and spilling the excess messages into hash tables at some point), and as far as I&#x27;ve seen, it takes some pretty pathological cases (e.g. an app with an unusually huge amount of classes and methods that consists of little actual code, yet relatively small number of actual object instances allocated) before the memory waste for sparse vtables start becoming anything remotely significant relative to an applications other memory usage or code size.