The Perl 6 Summary for the week ending 20030622
Welcome to my first anniversary issue of the Perl 6 Summary. Hopefully
there won't too many more anniversaries to celebrate before we have a
real, running Perl 6, but there's bound to be ongoing development after
that. My job is secure!
Because I can't think of anything better to do, I'll start with the
action on the perl6-internals list
Converting parrot to continuation passing style
The ongoing effort to convert Parrot to use/support continuation passing
style (CPS) at the assembler level continues. Jonathan Sillito offered
another patch implementing the require support, which Dan liked and
applied.
Klaas-Jan Stol wondered what he'd missed; last time he looked Parrot
wasn't doing continuation passing. He asked why Dan had chosen to go
down that route. Dan answered that he had realized that we had to save
off so much state that we essentially had a continuation anyway.
Explicitly going with continuation passing just made things more formal,
and wrapped up all the context saving behind a straightforward
interface. He promised a more detailed explanation later.
http://xrl.us/j7x
Portable way of finding libc, unbuffered reads
Clinton Pierce noted that the following code:
loadlib P1, /lib/libc.so.6
dlfunc P0, P1, system, it
set I0, 1
set S5, ls
invoke
end
just works, which simultaneously pleases and scares him silly. He
wondered if there was a good way of finding the standard C library on a
Unix system without scary hardwiring as in the fragment above. He also
wondered if there was an 'official' way of getting an unbuffered read
via parrot.
Jens Rieks came up with a gloriously evil way of finding libc. The
theory goes that Parrot is linked against libc, so you just have to
dlopen the running image and you can call libc functions to your
heart's content. To dlopen the running image you need to pass a NULL
pointer to the underlying loadlib so he offered a patch to core.ops
which interpreted an empty string as a pointer to NULL. Leo and Dan were
impressed and the patch (or something similar) was applied. I get the
feeling that Dan wants to do something a little less hacky to access the
current executable though...
Clint noted that the dlopen the running image by passing a null pointer
trick doesn't work with Windows, but outlined a workaround for that too.
Jen Rieks suggested a better Windows workaround.
Nobody came up with an approved way of doing getc, but once you have
libc loaded you can just use its getc.
http://xrl.us/j7y
OO, Objects
If you look in a fresh from CVS parrot directory you'll now find
object.ops, which will be the cause of much rejoicing in many places.
Dan's nailed the object spec down enough that he's started implementing
a few of the required ops. As he points out, what we have is hardly
sufficient, but everyone's got to start somewhere, the journey of a
thousand miles begins with but a single step, etc.
Judging by the number of comments (none), everyone was stunned into
silence.
http://xrl.us/j7z
More CPS shenanigans
I get the strong feeling that Leo Tötsch isn't entirely happy with the
new Continuation Passing Style regime. He's worried that the P6C tests
break, and that CPS subs are some 3 times slower for calling the sub.
This led into a discussion of what context really must go into a
continuation, whether we can get away with different classes of
continuation (hold more or less contextual information) and other ways
of possibly speeding things up.
I'm not sure Leo has been entirely convinced, but I'm confident that
Dan's not going to change his mind about this.
Leo later submitted a large patch which unifies the various subroutine
related PMCs to take into account CPS.
http://xrl.us/j72
Exceptions
Now that the rules for subs/methods etc are settling down, Dan outlined
his thoughts on exception handlers. If I'm understanding him correctly,
an exception handler is just a continuation that you invoke with the
exception as its only argument. There were no comments by the end of the
week.
http://xrl.us/j73
Meanwhile in perl6-language
The language list was quiet again. Maybe everyone was doing face to face
things at YAPC. Or on holiday. Or something.
printf like formatting in interpolated strings
Remember last week I mentioned that Luke Palmer had made a cool
suggestion about printf like formatting in string interpolation? (He
suggested a syntax like rx/expression but formatted(formatspec)/,
which I for one quite liked).
Edwin Steiner wasn't so keen, noting that Luke's suggestion was actually
more verbose than rx/sprintf formatspec, expression/. He wasn't
entirely
