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by rjsw 766 days ago
Maclisp on PDP-10 and Franz Lisp didn't, they used bibop type checking instead of tagged pointers.
2 comments

> Franz Lisp

Off topic, but that's probably the silliest name for a programming language I've seen. I love it!

That’s merely an elaboration on the same theme.
It isn't, pointers in Franz Lisp can be used unmodified in C.
But those pointers still have bits in them that indicate the type of the object that they point to. It is merely the case that the tag bits are chosen at run time so that they correspond to allocated memory regions, rather than being chosen ahead of time.
None of the bits in the pointer have been "stolen" though, which is the point of the referenced article, they are all still available to access the full address space of the CPU.
That doesn't mean that they aren’t still there, and don't tell you the type. It’s still a tagged pointer, and because all objects of the same type must be allocated out of the same page (or collection of pages), it still limits how much memory can be dedicated to objects of that type.