On Wed 18 Jan 2012 23:21, l...@gnu.org (Ludovic Courtès) writes:
> Andy Wingo <wi...@pobox.com> skribis:
>
>> On Wed 18 Jan 2012 22:18, l...@gnu.org (Ludovic Courtès) writes:
>>
>>> (('apply (f args))
>>> (apply (eval f env) (eval args env)))
>>
>> This is in primitive-eval (and here, `eval' is locally bound). Mark is
>> talking about R5RS `eval' (`scm_eval').
>
> OK, but ‘scm_eval’ is not recursive, so no wonder it’s not
> tail-recursive. :-)
>
> (I’m confident I’m missing something, but I just fail to see what. ;-))
Hee hee :) The point is that this should loop indefinitely:
(define (loop)
(eval '(loop) (current-module)))
(loop)
It doesn't, because the function that "eval" resolves to is implemented
in C. If we implemented it in Scheme, it still wouldn't work, because
it would be like:
(define (loop)
(with-fluids ((%%%current-module (current-module)))
(primitive-eval '(loop))))
(loop)
and the with-fluids makes it not tail recursive.
Andy
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