On Jun 28, 2005, at 17:23, Klaas-Jan Stol wrote:
hi,
I've been playing a bit with the new set_*/get_* ops that implement
the new calling conventions, according to pdd03.
If the number of passed arguments is larger than the number of
parameters the function takes, an exception is thrown (this is the
overflow case described in PDD03) (except when the final target is a P
register with the FLATTEN bit, then it just works like "foldup")
Yep
I wonder what the reason is to throw an exception. With dynamic
languages, you can't be sure what function you are calling (you can
set them dynamically, I must admit I don't know Perl, and therefore
don't know if this is an issue with Perl). Wouldn't it be easier to
just discard the values that are passed to the function? Obviously,
the function has only use for the number of parameters it has defined,
so it doesn't care about the extra values.
I'm pretty sure that we'll have an interpreter error setting
evenutually that will either warn or just ignore argument count
mismatch.
The same is true for underflow: why wouldn't you just set the targets
for which there is no value left (so too few arguments were passed) to
None?
Same with that.
Yet another question, but not directly relating to the new pdd03, but
in fact a question in general wrt calling conventions: pass by
ref/pass by value.
If I understood correctly, I, N and S registers are passed by value,
but P registers are passed by reference.
String registers are pointers too and passed by reference. But most of
the string operations have value semantics therefore it doesn't matter
much.
I couldn't find any possibility to pass PMCs by value; one would have
to create a new PMC in the called subroutine, and _assign_ the
passed-in argument to this newly created PMC. This may of course be
the desired behaviour for Perl and friends, but wouldn't it be neat to
have a possibility to pass PMCs by value as well? (This could easily
be indicated by the flags of the new opcodes set_args/returns and
get_params/results, I think).
This possibility would make Parrot more general.
Yep. That's just missing currently.
Kind regards,
klaas-jan
leo
