[17618] in Perl-Users-Digest
Perl-Users Digest, Issue: 5038 Volume: 9
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Dec 5 14:15:41 2000
Date: Tue, 5 Dec 2000 11:15:22 -0800 (PST)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Message-Id: <976043721-v9-i5038@ruby.oce.orst.edu>
Content-Type: text
Perl-Users Digest Tue, 5 Dec 2000 Volume: 9 Number: 5038
Today's topics:
Re: Sorting the result of a function <jrw32982@my-deja.com>
Re: Sorting the result of a function <jrw32982@my-deja.com>
Re: Sorting the result of a function <jeffp@crusoe.net>
Re: submit a HTML file using a textarea within a form nobull@mail.com
Triva Game via Perl <lmoran@wtsg.com>
Re: unsolved: <STDIN> (Anno Siegel)
Re: unsolved: <STDIN> (Anno Siegel)
Re: unsolved: <STDIN> <schneider@xtewa.de>
Re: unsolved: <STDIN> (Tad McClellan)
Re: unsolved: <STDIN> <schneider@xtewa.de>
Re: unsolved: <STDIN> <schneider@xtewa.de>
Re: What if $SIG{__DIE__} is occupied by other module? (Ilya Zakharevich)
Re: What if $SIG{__DIE__} is occupied by other module? nobull@mail.com
Digest Administrivia (Last modified: 16 Sep 99) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Tue, 05 Dec 2000 16:33:57 GMT
From: John Wiersba <jrw32982@my-deja.com>
Subject: Re: Sorting the result of a function
Message-Id: <90j5dl$9hv$1@nnrp1.deja.com>
garry@zvolve.com wrote:
> `sort f() ...' looks like `sort SUBNAME LIST' while `sort +f() ...'
> looks like `sort LIST'.
Maybe to the perl parser, but not to a human. s/sort/foo/g and then
tell me what "foo f()" looks like.
--
John Wiersba
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
Date: Tue, 05 Dec 2000 16:32:09 GMT
From: John Wiersba <jrw32982@my-deja.com>
Subject: Re: Sorting the result of a function
Message-Id: <90j5aa$9gq$1@nnrp1.deja.com>
garry@zvolve.com wrote:
> But not with the sort() parameter prototype that is described in
> perldoc -f sort:
...
> @sortedclass = sort byage @class;
But my code doesn't say "sort f @LIST". It says "sort f(...)". Is
there not a big visual and cognitive difference? "f(...)" looks like a
function call. "f @LIST" looks like a bare word followed by a list and
consequently is much less prone to misinterpretation.
See also my previous post in this thread where the phrase "looks like a
function, therefore it is a function" is bandied about.
> >> See the sort() entry in the perlfunc manual page.
> >
> >I don't see anything in there referring to this bizarre behavior.
>
> See above; it's the first prototype that is listed.
I don't see how a prototype for sort() is supposed to explain that you
cannot pass as an argument to sort() the result of a function-call
written using "normal" function-call syntax.
Bottom line:
I believe I understand what perl is doing. I believe I understand why
perl is doing it. But that doesn't make it right.
You're saying, in effect, that:
foo f(...)
is a call to f() whose list-context result is passed to foo(). Except
if foo == sort, in which case it's a call to sort() passing it a
function name f and a list.
I really find it incredible that a) a language could be designed to work
this way, and b) people would defend it as if it made sense.
(Sorry, Garry, if you're not really defending perl. But I haven't
heard even a single voice say, "Yea, you're right, it's unbelievably
ugly; but that's the way it is and here's why...".)
--
John Wiersba
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
Date: Tue, 5 Dec 2000 13:54:29 -0500
From: Jeff Pinyan <jeffp@crusoe.net>
Subject: Re: Sorting the result of a function
Message-Id: <Pine.GSO.4.21.0012051347280.5826-100000@crusoe.crusoe.net>
[posted & mailed]
On Dec 5, John Wiersba said:
>> `sort f() ...' looks like `sort SUBNAME LIST' while `sort +f() ...'
>> looks like `sort LIST'.
>
>Maybe to the perl parser, but not to a human. s/sort/foo/g and then
>tell me what "foo f()" looks like.
foo is not sort. There are things in Perl that have specific rules and
contexts applied to them.
sort this @that;
sort this (@that);
sort this(@that);
all do the same thing -- that is, use 'this' as the name of a comparison
function, and @that as the list of items to sort.
If you place a unary + in front of this(@that), perl's lexer knows not to
interpret 'this' as the SUBNAME part.
It's a matter of context, and understanding that you can't get what you
want all the time.
--
Jeff "japhy" Pinyan japhy@pobox.com http://www.pobox.com/~japhy/
CPAN - #1 Perl Resource (my id: PINYAN) http://search.cpan.org/
PerlMonks - An Online Perl Community http://www.perlmonks.com/
The Perl Archive - Articles, Forums, etc. http://www.perlarchive.com/
------------------------------
Date: 05 Dec 2000 17:52:23 +0000
From: nobull@mail.com
Subject: Re: submit a HTML file using a textarea within a form
Message-Id: <u9zoia7o2w.fsf@wcl-l.bham.ac.uk>
Karsten Hachmeister <Karsten@Hachmeister-Online.de> writes:
> I have a problem...
Please post a minimal (strict, warning free) script that illustrates
your problem. Anything else is a waste of your time and ours.
The following script does not reproduce your problem here, does it
reproduce your problem there?
#!/usr/bin/perl -w
use strict;
use CGI ':standard';
print header,start_html,start_form,
textarea('foo'),submit,end_form,end_html;
__END__
--
\\ ( )
. _\\__[oo
.__/ \\ /\@
. l___\\
# ll l\\
###LL LL\\
------------------------------
Date: Tue, 05 Dec 2000 13:14:25 -0500
From: Lou Moran <lmoran@wtsg.com>
Subject: Triva Game via Perl
Message-Id: <0k0q2t8e99j07vvqbkqoql8i0psanf6fdc@4ax.com>
---I have this idea I will write a trivia game with perl.
#!/usr/bin/perl -w
use strict;
print "Welcome to the Trivia Game\n\n";
print "Answer questions with one uppercase number, \n\n";
print "What is your favorite color?\n\n";
print "10. Yellow, 11. Blue, 12. Green, 13. I don't know\n\n";
my $answer=<STDIN>;
chomp $answer;
my $canswer=10;
unless ($answer eq "10") {
print "$answer is wrong, please try again.\n";
}
if ($answer eq "10"){
print "Good work! \n\n";
}
***yes, there would be a die statement if they didn't use a number to
answer... yes there would be a while statement so the program didn;t
just throw them out when they answer...
---The perl question is I would want to maintain the question and
answer database somewhere else to add and subtract questions. I know
how to read a list (ala Secret Word List in LP on Win32 Syetems) but I
don't know how to get list info to display <print> (or better yet make
it "become" HTML code, in fact I have no idea how to make anything
HTML in perl.) I have looked in perldoc but like find in *nix I
haven't really mastered that (and I lent someone who can actually do
useful things with perl my LPOW32S book.)
any help would be well, helpful.
mmmmm... pointy
lmoran@wtsg.com
------------------------------
Date: 5 Dec 2000 14:26:14 -0000
From: anno4000@lublin.zrz.tu-berlin.de (Anno Siegel)
Subject: Re: unsolved: <STDIN>
Message-Id: <90itu6$1u5$1@lublin.zrz.tu-berlin.de>
SimBean <schneider@xtewa.de> wrote in comp.lang.perl.misc:
>Am I just to stupid?
>Please tell me where to find that faq (it obviously isn't on perl.com)
>and I won't bother you anymore ...
What about http://www.perl.com/pub/v/faqs? The link is right on the
top page.
Anno
------------------------------
Date: 5 Dec 2000 14:47:57 -0000
From: anno4000@lublin.zrz.tu-berlin.de (Anno Siegel)
Subject: Re: unsolved: <STDIN>
Message-Id: <90iv6t$21e$1@lublin.zrz.tu-berlin.de>
SimBean <schneider@xtewa.de> wrote in comp.lang.perl.misc:
>Hi,
>
>hmh, I think it doesn't work the way it should - but why?
>
>
>That's what I am doing:
>
>
>#!perl -w
>use strict;
>
>my $input;
>open( INPUT, "<&STDIN" );
>select( INPUT ); $| = 1;
$| only affects output. It is useless here.
>while(1)
>{
> print STDOUT $input . "\n" if( sysread ( INPUT, $input, 1 ) );
>}
>close ( INPUT );
>
>and it still reads the input only after hitting enter...
The Term::ReadKey module from CPAN does what you want. Also, find
"How do I check whether input is ready on the keyboard?" in perlfaq8.
Even though it doesn't seem to apply directly, it shows you how
to get ReadKey in the right mode.
Anno
------------------------------
Date: Tue, 05 Dec 2000 14:59:16 GMT
From: SimBean <schneider@xtewa.de>
Subject: Re: unsolved: <STDIN>
Message-Id: <90ivs0$4oa$1@nnrp1.deja.com>
> What about http://www.perl.com/pub/v/faqs? The link is right on the
> top page.
I didn't know he was talking about that, because I searched perl.com
for the subject and it didn't show me any link to that faq. And I could
have bet I had searched the whole faq for that subject before I posted
the message ...
Anyway: it doesn't work the way they describe it! :)
Is it maybe because I am using WinNT??
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
Date: Tue, 5 Dec 2000 09:54:58 -0500
From: tadmc@metronet.com (Tad McClellan)
Subject: Re: unsolved: <STDIN>
Message-Id: <slrn92q0e2.ni3.tadmc@magna.metronet.com>
SimBean <schneider@xtewa.de> wrote:
>
>> >I would just check if there _is_ input
>> Perl FAQ, part 8:
>> "How do I check whether input is ready on the keyboard?"
>> You inch ever closer to earning yourself a killfile entry.
>> Better stop doing that quick before it gets to be too late...
>Ok, even after _knowing_ what to look for, I didn't find it!
>Am I just to stupid?
What about those steps you claim to follow?
A Deja power search for "FAQ" in c.l.p.misc finds:
Subject: [Perl] How to find the Perl FAQ
Posted here 3 days ago (December 2).
>Please tell me where to find that faq (it obviously isn't on perl.com)
>and I won't bother you anymore ...
You won't be bothering me anymore for a few months regardless
of whether you find them or not :-(
>btw: I hope that there are more tolerant people out there that know
>perl!!!
For your sake, I hope so too, since I won't be seeing your posts
for a while.
Expecting that folks will just let you take cuts in line seems
an unreasonable expectation though...
-----------------------------------
In article <1995Nov9.193745.13694@netlabs.com>, lwall@netlabs.com (Larry
Wall) wrote: ...
<Larry> [snip] I view a programming language as a place to be
<Larry> explored, like Disneyland. You don't need to have a lot of preparation
<Larry> to explore a theme park. You do have to go along with the crowd
<Larry> control measures, though. In a sense, each ride has its own
<Larry> prerequisites--if you cut in line, you risk getting tossed out of the
<Larry> park.
<Larry>
<Larry> What we have here in this newsgroup is a failure in crowd control.
<Larry> Reading the FAQ is like staying in line--it's something you should
<Larry> learn in kindergarten. Usenet needs a better kindergarten.
-----------------------------------
--
Tad McClellan SGML consulting
tadmc@metronet.com Perl programming
Fort Worth, Texas
------------------------------
Date: Tue, 05 Dec 2000 15:49:36 GMT
From: SimBean <schneider@xtewa.de>
Subject: Re: unsolved: <STDIN>
Message-Id: <90j2qd$7c5$1@nnrp1.deja.com>
> >Hi,
> >
> >hmh, I think it doesn't work the way it should - but why?
> >
> >
> >That's what I am doing:
> >
> >
> >#!perl -w
> >use strict;
> >
> >my $input;
> >open( INPUT, "<&STDIN" );
> >select( INPUT ); $| = 1;
> $| only affects output. It is useless here.
That's what they said in the faq! I thought it would trigger
flushing ... ?!
> The Term::ReadKey module from CPAN does what you want. Also, find
> "How do I check whether input is ready on the keyboard?" in perlfaq8.
> Even though it doesn't seem to apply directly, it shows you how
> to get ReadKey in the right mode.
Yes, I tried that, too. It seems like this module isn't installed on my
pc. If there is no other way to solve the problem, I am going to get it.
btw: will it work on a WinNT-pc??
Ciao,
SimBean.
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
Date: Tue, 05 Dec 2000 16:56:00 GMT
From: SimBean <schneider@xtewa.de>
Subject: Re: unsolved: <STDIN>
Message-Id: <90j6ms$au4$1@nnrp1.deja.com>
> For your sake, I hope so too, since I won't be seeing your posts
> for a while.
>
> Expecting that folks will just let you take cuts in line seems
> an unreasonable expectation though...
Please see my email about this ...
Ciao,
SimBean.
Sent via Deja.com http://www.deja.com/
Before you buy.
------------------------------
Date: 5 Dec 2000 18:37:28 GMT
From: ilya@math.ohio-state.edu (Ilya Zakharevich)
Subject: Re: What if $SIG{__DIE__} is occupied by other module?
Message-Id: <90jcl8$ku5$1@charm.magnus.acs.ohio-state.edu>
[A complimentary Cc of this posting was sent to Bart Lateur
<bart.lateur@skynet.be>],
who wrote in article <mplp2ts0j4p0k1qqirf1jf0ube36v9m47l@4ax.com>:
> >So do not set $SIG{__DIE__}, use eval {} and all will be well.
>
> And what happened to TMTOWTDI?
TMTOWT understand TMTOWTDI.
> $SIG{__DIE__}, IMO, is a hook which serves to customize the error
> message, or at leats, the printout of the error message. eval BLOCK
> serves to *prevent* an error message, and fatality.
Nope. eval BLOCK is used *to intercept* the error condition, not to
prevent it. Having intercepted it, you have a complete right to
inspect it, customize it, and rethrow the error.
So there is indeed a lot of similarity between the functionality of
$SIG{__DIE__} and eval BLOCK. The largest difference is that
$SIG{__DIE__} is called first, and eval BLOCK are called after this
(inside out, if rethrowing).
This makes $SIG{__DIE__} more suitable only in the situations when you
want to see the original error text, *and* want to see errors which
were catched and not rethrown.
> So why is a callback function to customize the error output
> even called, when error messages aren't supposed to be printed? This is
> nonsense.
See above.
> BS. Now, there are at least two modules available from CPAN where
> there's a fatal error if you had set $SIG{__DIE__}. So you claim this is
> a bug in these modules? I think not.
Oh yes, I see. A misbehaviour of a module cannot be a module's fault
as far as it is on CPAN?
Ilya
------------------------------
Date: 05 Dec 2000 18:30:16 +0000
From: nobull@mail.com
Subject: Re: What if $SIG{__DIE__} is occupied by other module?
Message-Id: <u9vgsy7mbr.fsf@wcl-l.bham.ac.uk>
Bart Lateur <bart.lateur@skynet.be> writes:
> nobull@mail.com wrote:
>
> >Bart Lateur <bart.lateur@skynet.be> writes:
> >
> >> >eval{} is the proper (stackable) way to catch exceptions.
> >>
> >> No: eval() is the CAUSE of the problem.
> >
> >No - mixing the two mechanisms of trapping __DIE__ exceptions is the
> >cause of the problem. If you had used only eval{} you'd not have a
> >problem.
>
> >So do not set $SIG{__DIE__}, use eval {} and all will be well.
>
> And what happened to TMTOWTDI?
TMTOWTDI with IO too, but if you mix buffered and unbuffered IO
expect problems unless you take precautions.
> $SIG{__DIE__}, IMO, is a hook which serves to customize the error
> message, or at leats, the printout of the error message. eval BLOCK
> serves to *prevent* an error message, and fatality.
There's no reason not to wrap your whole program in an eval{}. This
is the C++ way.
> So why is a callback function to customize the error output even
> called, when error messages aren't supposed to be printed? This is
> nonsense.
IMO, for most purposes $SIG{__DIE__} is a relic, superceeded by eval.
I'd only resort to it when the higher level mechanism could not be
used - such as for trapping errors during the initial compliation
phase.
> $SIG{__DIE__}, as a hook, is layered on top op the standard behaviour.
> Currently, eval BLOCK is layered *between* $the default behaviour, and
> the $SIG{__DIE__} handler. It should really be, IMO, layered *on top* of
> it, instead.
I don't think I understand your use of "on top". I'm not sure if I
would agree with you if I understood you.
> In a way, it'd even make sense if eval made use of the $SIG{__DIE__}
> hook mechanism.
I'm now undecided if I'd like to see eval localize $SIG{__DIE__}.
When this thread started out I was definitely opposed to this because
I was affraid it was backward incompatible change but now I've found
the manual warns that this backward incompatible change I see less
reason why it should't be done.
It would not make sense if eval made use of the $SIG{__DIE__} hook
mechanism because then setting a $SIG{__DIE__} handler inside an
eval{} block would then have the same counterintuative behaviour.
We'd just be trading one counterintuative behaviour for another.
> >It is all well documented, as is the $^S work-round so I see no urgent
> >need to fix it even if the docs warn that one day it may be fixed.
>
> BS. Now, there are at least two modules available from CPAN where
> there's a fatal error if you had set $SIG{__DIE__}. So you claim this is
> a bug in these modules? I think not.
No, the bug is in your __DIE__ handler. The docs on writing die
handlers tell you of the need to check $^S and you didn't do it.
> Isn't that just a bit too low level?
$SIG{__DIE__} _is_ a low-level constuct. Your __DIE__ handler may get
executed while the parser in an inconsistant state. If that isn't low
level I don't know what is. If you don't want to get into low level
stuff then you should be using eval.
--
\\ ( )
. _\\__[oo
.__/ \\ /\@
. l___\\
# ll l\\
###LL LL\\
------------------------------
Date: 16 Sep 99 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 16 Sep 99)
Message-Id: <null>
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------------------------------
End of Perl-Users Digest V9 Issue 5038
**************************************
