Re: More on Lisp structures performance
"Tim Bradshaw (as tfb at cley dot com)" <[email protected]>
| Newsgroups | gmane.lisp.lispworks.general |
|---|---|
| Message-ID | <[email protected]> |
On 24 Jan 2026, at 19:29, Yuri Davidovsky <[email protected]> wrote: > > But if you decide to use 4 bits for a tag, then it means you can’t retrieve a value from the heap easily because it won’t be a valid pointer anymore. Yes, amazingly that is what SBCL does. I mean you could just believe me, or you could, you know, check: "Objects allocated on the Lisp heap are aligned to a double-word boundary, leaving the low-order bits (which would normally identify a particular octet within the first two words) available for use to hold type information. This turns out to be three bits on 32-bit systems and four bits on 64-bit systems." >From https://github.com/sbcl/sbcl/blob/master/doc/internals/objects-in-memory.texinfo Gosh, who knew? _______________________________________________ Lisp Hug - the mailing list for LispWorks users [email protected] http://www.lispworks.com/support/lisp-hug.html