r3wp [groups: 83 posts: 189283]
  • Home
  • Script library
  • AltME Archive
  • Mailing list
  • Articles Index
  • Site search
 

World: r3wp

[!REBOL3]

Ladislav
12-Mar-2010
[1532x2]
but, anyway, when we are at discussing it, isn't there a proposal 
to improve the named throw behaviour?
Is it supposed to actually "emulate" a definitionally scoped catch/throw?
Andreas
12-Mar-2010
[1534]
Named catch/throw, you mean?
Ladislav
12-Mar-2010
[1535]
yes
Andreas
12-Mar-2010
[1536]
I'm not sure.
Ladislav
12-Mar-2010
[1537]
Nevertheless, my guess is, that:
1) named throw is not used by Rebol users
2) it can be safely discarded therefore
Andreas
12-Mar-2010
[1538x2]
Yes, it actually seems to be that way.
I grepped through the R2/R3 mezzanines and some library scripts, 
and this seems to confirm your guess.
Ladislav
12-Mar-2010
[1540]
will post that to the blog too
Andreas
12-Mar-2010
[1541x4]
I think it actually Boils down to the question what the named catch/throw 
is or should actually
.. be used for.
Is used for: not much. Should be used for: not much as well, as I 
think we could have better solutions for most error handling scenarios.
This would then leave us with the "classical" Common Lisp-style use 
of named catch/throw for non-local exits. And for this use-case, 
a definitionally scoped name would certainly be the right thing to 
do, imho.
Gregg
12-Mar-2010
[1545]
Maarten and I used a named throw in a proejct for Qtask, but I don't 
use it much. The question is, *should* we use it more, and what are 
the scenarios? It does make some handling read cleaner to me. 

Maybe Carl can say what he envisioned when he designed it.
BrianH
12-Mar-2010
[1546x3]
Ladislav, your B-CATCH/B-THROW example is similar to what I suggested 
in an earlier comment, but in code form. Nice code :)
And I use names CATCH and THROW.
I never tried to catch a named throw without a named catch. If that 
is possible, that is a major bug and should be reported.
Gregg
12-Mar-2010
[1549]
It's possible in R2. CATCH returns the name it caught.
BrianH
12-Mar-2010
[1550x4]
It's possible in R3 as well. I'll report it later.
Extept CATCH returns the value, not the name. Even worse.
Andreas, in R3 :result means GET/any 'result.
Sorry, Ladislav mentioned that already.
Gregg
12-Mar-2010
[1554]
Is it a bug, or by design though? i.e. it's a general catch. If the 
name gets lost on a named throw, that seems an obvious oversight 
in the design.
BrianH
12-Mar-2010
[1555x2]
That sounds like an error that should be reported by the console. 
A named throw that doesn't have a corresponding named catch should 
be treated like it doesn't have a catch at all.
We use THROW/name to write sandboxed replacements for the unwind 
functions, non-local dynamic escape functions, etc. But that only 
works if CATCH doesn't catch it.
Gregg
12-Mar-2010
[1557]
If that was the original design intent, then I agree.
BrianH
12-Mar-2010
[1558x4]
Reported in bug#1518.
Andreas, the meaning of "non-local" we have been using is code that 
is *not* in a nested block or paren. Instead, the code is in another 
function, a block defined elsewhere, whatever. Definitional scoping 
will only work for local code, meaning code that is in nested blocks. 
We have to define locality relative to the catch, not the throw, 
because the catch function is what defines the scoping.
Gregg, CATCH is not a general catch: There is already the /quit option 
that makes it catch more than it normally would.
Steeve, you might be amused to find out that the DO intrinsic currently 
depends on bug#1509 and does need a [throw] attribute. Though it 
still wouldn't work with definitional RETURN because of binding issues. 
C'est la vie.
Steeve
12-Mar-2010
[1562]
I'm working on an FIRE effect for R3, that's how I might be amused 
:)
Gabriele
13-Mar-2010
[1563]
Brian, if a simple CATCH should not catch named throws then we need 
a CATCH/ALL (not sure if /QUIT should be it).
Andreas
13-Mar-2010
[1564x2]
Gabriele, Brian requested such a thing (CATCH/ALL) as bug#1520.
Though he wants bug#1520 to catch all other unwinds (BREAK, CONTINUE, 
RETURN, EXIT) as well, to which I see no merit.
BrianH
13-Mar-2010
[1566x3]
The advantage to that is because on those rare occasions when you 
actually need to catch all THROW and THROW/name unwinds, you most 
likely need to catch the rest too. You might note that the emergency 
exceptions - HALT, QUIT/now, errors - aren't proposed to be caught, 
because the cleanup code would likely interfere with error recovery 
code or the debugging process.
Most of the time you really don't want THROW/name caught by code 
that it isn't intended for. When you really want to catch off-topic 
stuff, you want to catch everything.
However, HALT is used for debugging (which is why CATCH/quit doesn't 
catch it), QUIT/now is supposed to always quit, and you want errors 
to get through so you see them, so those make sensible exceptions.
Paul
14-Mar-2010
[1569x2]
Can someone else confirm if they get a problem with the following 
ajoin [newline "blah" crlf]
I don't get the problem on windows but do get it on my webhost (linux)
BrianH
14-Mar-2010
[1571]
It looks good here on Windows. What problem do you see?
Paul
14-Mar-2010
[1572]
yeah works find on windows
BrianH
14-Mar-2010
[1573x2]
Can you copy the Linux output here?
(I have a theory, but need confirmation)
Paul
14-Mar-2010
[1575x4]
recreating - hold on
weird - this time it works.
before I would get "^^/blah^M^/"
I would get a double ^
BrianH
14-Mar-2010
[1579]
Strange.
Paul
14-Mar-2010
[1580]
yeah not sure why
BrianH
14-Mar-2010
[1581]
Heisenbug?