Ludovic Courtès <l...@gnu.org> writes:
> Hi David,
>
> David Kastrup <d...@gnu.org> skribis:
>
>> In Scheme, symbols can be compared using eq? for equality. However,
>> since they have garbage-collected content attached, they do not meet the
>> predicate SCM_IMP in the short-circuit evaluation at the start of equal?
>> This means that unequal symbols compared using equal? fall through a
>> whole bunch of tests and end up in a general structural comparison
>> comparing their underlying string names.
>
> ‘equal?’ starts by checking for eq-ness, which LGTM:
>
> SCM
> scm_equal_p (SCM x, SCM y)
> #define FUNC_NAME s_scm_i_equal_p
> {
> SCM_CHECK_STACK;
> tailrecurse:
> SCM_TICK;
> if (scm_is_eq (x, y))
> return SCM_BOOL_T;
>
> Or were you referring to something else?
I repeat: "This means that UNEQUAL symbols compared using equal? fall
through a whole bunch of tests and end up in a general structural
comparison comparing their underlying string names".
Lots of searches _end_ with an equal comparison (which is fast) but do a
lot of unequal comparisons before that (which is slow, even though
symbols that are not eq? will also not be equal?, so if you know you are
checking _symbols_, if they are not eq? you are done).
Symbols comparing as _unequal_ have no special path in equal?.
--
David Kastrup
