[Armedbear-devel] Tail recursion

[Vibhu Mohindra]

Hi Erik,

No, no idea or numbers about the fraction that would benefit.

The "optimisation" in TCO is different from its traditional sense, which is
usually "just" to provide a constant factor improvement in speed/memory.
TCO by contrast, allows or doesn't allow a programmer to use a certain
programming technique: recursion.

I use recursion a lot, and when I moved to ABCL, I found that a lot of code
broke on lists as short as a few thousand elements.

So I'm not referring so much to ABCL or its implementation as to a Lisp
program. A portable Lisp programmer can't rely on TCO being available. So
using defun/tro [1] lets them remain portable across Lisps.

It's probably not too hard to also optimise mutual recursion (f->g->f) in a
labels clause using a similar macro to defun/tro.

When I say I'm not referring specifically to ABCL, it means that if ABCL
implemented TCO, everything I wrote would just move over to another
(present or future) non-TCO ANSI Common Lisp's discussion forum when
someone enquired about it :-) .

Sorry about the delay. I haven't yet mastered this newsgroup's
(mailing-list's?) interface, and thought my last message hadn't even gone
through.

[1]: was deftro

Vibhu
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