On Mon, 08 Jun 2015 18:04:44 -0700, <d...@gnu.org> wrote:
No dice. The main problem is dealing with all combinations of running
out of signature and running out of available arguments. If you treat
the optional argument skipping in an inner loop, you may still run out
of signature, and in that case you still need to treat the case where
you have simultaneously run out of arguments (namely because the
non-matching argument triggering the skipping was \default aka
*unspecified) separately _and_ break out of all loops. Since you have
already fetched the next signature bit (since you would not know whether
it was optional and skipping should continue), you can't return to the
main loop which would fetch it again but need to clad the whole in one
while (scm_is_false (scm_call_1 (pred, arg))) of its own. Treating all
the terminating condition combinations in inner loop and outer loop
separately causes the control structures to fray apart more than the
"skipping" flag does, to the degree where the cleanest solution to
handle one of the innermost loop termination conditions with a goto
statement.
Well, the inner loop can decide whether to continue by peeking-ahead at the
next entry in the signature. Then the jobs of the inner/outer loops remain
clean.
Some people don't like side-effects in loop-control conditionals
while (scm_is_pair (scm_cdr (signature)) // more slots ?
&& scm_is_pair (scm_cadr (signature)) // next one optional ?
&& (signature = scm_cdr (signature)));// deal with it now.
so maybe I'll use test-in-the-middle loop, but that needs only break one loop.
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