* About zsh-users 8489 (exception handling)
@ 2005-09-27 23:47 DervishD
2005-09-28 2:42 ` Bart Schaefer
0 siblings, 1 reply; 5+ messages in thread
From: DervishD @ 2005-09-27 23:47 UTC (permalink / raw)
To: Zsh Users
Hi all :)
In zsh-users 8489 Bart Schaeffer proposes using this syntax:
{ ${:?THROW} } 2>/dev/null
instead of this one:
{ ${*ERROR*} } 2>/dev/null
for generating the exception in "throw" function, since the
latter may become valid syntax in the future.
Unfortunately, that doesn't work because ${:?...} *exits* from
the shell, so the valid syntax would be:
( ${:?THROW} ) 2>/dev/null
For me, using a subshell just to generate the exception seems a
bit excessive. Is there any other way of generating an error (the
exception) without using a subshell and without using current invalid
syntax that could become valid in the future?
Thanks a lot :)
Raúl Núñez de Arenas Coronado
--
Linux Registered User 88736 | http://www.dervishd.net
http://www.pleyades.net & http://www.gotesdelluna.net
It's my PC and I'll cry if I want to...
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: About zsh-users 8489 (exception handling)
2005-09-27 23:47 About zsh-users 8489 (exception handling) DervishD
@ 2005-09-28 2:42 ` Bart Schaefer
2005-09-28 8:43 ` DervishD
0 siblings, 1 reply; 5+ messages in thread
From: Bart Schaefer @ 2005-09-28 2:42 UTC (permalink / raw)
To: Zsh Users
On Sep 28, 1:47am, DervishD wrote:
:
: In zsh-users 8489 Bart Schaeffer proposes using this syntax:
:
: { ${:?THROW} } 2>/dev/null
:
: Unfortunately, that doesn't work because ${:?...} *exits* from
: the shell
Not in an interactive shell, it doesn't. However ...
: Is there any other way of generating an error (the exception) without
: using a subshell and without using current invalid syntax that could
: become valid in the future?
Yes. If you declare (at the top of the throw function)
readonly THROW
then
THROW= 2>/dev/null
causes the error, which can be caught with "always". You don't even
need the extra layer of { }. I like this a lot, because it uses only
valid syntax that is pretty much guaranteed always to remain valid.
I think EXCEPTION should also be declared with "typeset -g", so that
makes the complete function look like:
throw() {
typeset -g EXCEPTION="$1"
readonly THROW
if (( TRY_BLOCK_ERROR == 0 )); then
# We are throwing an exception from the middle of an always-block.
# We can do this by restoring the error status from the try-block.
# (I am not convinced I ever intended this to work, but it does...)
(( TRY_BLOCK_ERROR = 1 ))
fi
# Raise an error, but don't show an error message.
# This is a bit of a hack. (Surprised?)
THROW= 2>/dev/null
}
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: About zsh-users 8489 (exception handling)
2005-09-28 2:42 ` Bart Schaefer
@ 2005-09-28 8:43 ` DervishD
2005-09-28 15:18 ` Bart Schaefer
0 siblings, 1 reply; 5+ messages in thread
From: DervishD @ 2005-09-28 8:43 UTC (permalink / raw)
To: Bart Schaefer; +Cc: Zsh Users
Hi Bart :)
You came to the rescue, as always ;)
* Bart Schaefer <schaefer@brasslantern.com> dixit:
> On Sep 28, 1:47am, DervishD wrote:
> :
> : In zsh-users 8489 Bart Schaeffer proposes using this syntax:
> :
> : { ${:?THROW} } 2>/dev/null
> :
> : Unfortunately, that doesn't work because ${:?...} *exits* from
> : the shell
> Not in an interactive shell, it doesn't. However ...
But I use (or will use) throw mainly in scripts, and that makes
the script to exit. And probably the 90% of throw/catch usage will
take place in scripts, not in interactive shells...
> : Is there any other way of generating an error (the exception) without
> : using a subshell and without using current invalid syntax that could
> : become valid in the future?
>
> Yes. If you declare (at the top of the throw function)
>
> readonly THROW
>
> then
>
> THROW= 2>/dev/null
>
> causes the error, which can be caught with "always". You don't even
> need the extra layer of { }. I like this a lot, because it uses only
> valid syntax that is pretty much guaranteed always to remain valid.
That's VERY clever, dude :))) I like this solution a lot :)
> I think EXCEPTION should also be declared with "typeset -g", so that
> makes the complete function look like:
But the function will work correctly even without "typeset -g",
wouldn't it? Wouldn't be needed "typeset -g" in "catch" too for the
CAUGHT parameter?
Thanks a lot for your answer :)
Raúl Núñez de Arenas Coronado
--
Linux Registered User 88736 | http://www.dervishd.net
http://www.pleyades.net & http://www.gotesdelluna.net
It's my PC and I'll cry if I want to...
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: About zsh-users 8489 (exception handling)
2005-09-28 8:43 ` DervishD
@ 2005-09-28 15:18 ` Bart Schaefer
2005-09-29 10:31 ` DervishD
0 siblings, 1 reply; 5+ messages in thread
From: Bart Schaefer @ 2005-09-28 15:18 UTC (permalink / raw)
To: Zsh Users
On Sep 28, 10:43am, DervishD wrote:
}
} > I think EXCEPTION should also be declared with "typeset -g"
}
} But the function will work correctly even without "typeset -g",
} wouldn't it?
Yes. It's just making it obvious that a "local" was not forgotten.
} Wouldn't be needed "typeset -g" in "catch" too for the
} CAUGHT parameter?
I'd probably put one there, yes. I hadn't looked again at "catch".
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: About zsh-users 8489 (exception handling)
2005-09-28 15:18 ` Bart Schaefer
@ 2005-09-29 10:31 ` DervishD
0 siblings, 0 replies; 5+ messages in thread
From: DervishD @ 2005-09-29 10:31 UTC (permalink / raw)
To: Bart Schaefer; +Cc: Zsh Users
Hi Bart :)
* Bart Schaefer <schaefer@brasslantern.com> dixit:
> On Sep 28, 10:43am, DervishD wrote:
> } > I think EXCEPTION should also be declared with "typeset -g"
> }
> } But the function will work correctly even without "typeset -g",
> } wouldn't it?
> Yes. It's just making it obvious that a "local" was not forgotten.
Ok, I see then :)
Thanks a lot again :)
Raúl Núñez de Arenas Coronado
--
Linux Registered User 88736 | http://www.dervishd.net
http://www.pleyades.net & http://www.gotesdelluna.net
It's my PC and I'll cry if I want to...
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2005-09-29 10:31 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2005-09-27 23:47 About zsh-users 8489 (exception handling) DervishD
2005-09-28 2:42 ` Bart Schaefer
2005-09-28 8:43 ` DervishD
2005-09-28 15:18 ` Bart Schaefer
2005-09-29 10:31 ` DervishD
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/zsh/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).