passing "#" into subroutine

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passing "#" into subroutine

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passing "#" into subroutine

Postby ela » Thu, 07 May 2009 01:15:08 GMT 

I find $commenttag prints out nothing, what's the problem? I have to escape 
pound....?


open( my $FPM, '<', "inputfile.txt");
$lineM = <$FPM>;

while (&Nextline($lineM, "#", "<Models>")) {
    $lineM = <$FPM>;
}

sub Nextline {
my ($line, $commenttag, $pattern) = @_;
print "C:$commentag"; print $pattern;<STDIN>;

   if ($line =~ /^$commenttag/) {
        return 1;
    }
    if ($line =~ /$pattern/) {
        return 0;
    } else {
        return 1;
    }
}
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Re: passing "#" into subroutine

Postby Tad J McClellan » Thu, 07 May 2009 01:35:41 GMT 





Your code does not attempt to output $commenttag.

Your code outputs $commentag.

If you had "use strict" turned on, then perl would have found this bug for you.




You have not enabled warnings and strictures.

    use warnings;
    use strict;

This has been pointed out to you before.

You should start doing it.




Did it start working when you escaped pound?

No?

Then that is not the problem.




You should always, yes *always*, check the return value from open():

    open my $FPM, '<', 'inputfile.txt' 
        or die "could not open 'inputfile.txt' $!';




You should not use ampersands on subroutine calls unless you know
what it means, and what it means is what you want. It seldom is.

   while ( Nextline($lineM, '#', '<Models>') ) {




perl would have found the bug for you, if you had only asked it to.


Have you seen the Posting Guidelines that are posted here frequently?


-- 
Tad McClellan
email: perl -le "print scalar reverse qq/moc.noitatibaher\100cmdat/"
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2.FAQ 4.68 Why does passing a subroutine an undefined element in a hash create it?

3.FAQ 4.67 Why does passing a subroutine an undefined element in a hash create it? 

This message is one of several periodic postings to comp.lang.perl.misc
intended to make it easier for perl programmers to find answers to
common questions. The core of this message represents an excerpt
from the documentation provided with Perl.

--------------------------------------------------------------------

4.67: Why does passing a subroutine an undefined element in a hash create it?

    If you say something like:

        somefunc($hash{"nonesuch key here"});

    Then that element "autovivifies"; that is, it springs into existence
    whether you store something there or not. That's because functions get
    scalars passed in by reference. If somefunc() modifies $_[0], it has to
    be ready to write it back into the caller's version.

    This has been fixed as of Perl5.004.

    Normally, merely accessing a key's value for a nonexistent key does
    *not* cause that key to be forever there. This is different than awk's
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--------------------------------------------------------------------

Documents such as this have been called "Answers to Frequently
Asked Questions" or FAQ for short.  They represent an important
part of the Usenet tradition.  They serve to reduce the volume of
redundant traffic on a news group by providing quality answers to
questions that keep coming up.

If you are some how irritated by seeing these postings you are free
to ignore them or add the sender to your killfile.  If you find
errors or other problems with these postings please send corrections
or comments to the posting email address or to the maintainers as
directed in the perlfaq manual page.

Note that the FAQ text posted by this server may have been modified
from that distributed in the stable Perl release.  It may have been
edited to reflect the additions, changes and corrections provided
by respondents, reviewers, and critics to previous postings of
these FAQ. Complete text of these FAQ are available on request.

The perlfaq manual page contains the following copyright notice.

  AUTHOR AND COPYRIGHT

    Copyright (c) 1997-2002 Tom Christiansen and Nathan
    Torkington, and other contributors as noted. All rights 
    reserved.

This posting is provided in the hope that it will be useful but
does not represent a commitment or contract of any kind on the part
of the contributers, authors or their agents.

4.FAQ 4.67: Why does passing a subroutine an undefined element in a hash create it? 

This message is one of several periodic postings to comp.lang.perl.misc
intended to make it easier for perl programmers to find answers to
common questions. The core of this message represents an excerpt
from the documentation provided with Perl.

--------------------------------------------------------------------

4.67: Why does passing a subroutine an undefined element in a hash create it?

    If you say something like:

        somefunc($hash{"nonesuch key here"});

    Then that element "autovivifies"; that is, it springs into existence
    whether you store something there or not. That's because functions get
    scalars passed in by reference. If somefunc() modifies $_[0], it has to
    be ready to write it back into the caller's version.

    This has been fixed as of Perl5.004.

    Normally, merely accessing a key's value for a nonexistent key does
    *not* cause that key to be forever there. This is different than awk's
    behavior.



--------------------------------------------------------------------

Documents such as this have been called "Answers to Frequently
Asked Questions" or FAQ for short.  They represent an important
part of the Usenet tradition.  They serve to reduce the volume of
redundant traffic on a news group by providing quality answers to
questions that keep coming up.

If you are some how irritated by seeing these postings you are free
to ignore them or add the sender to your killfile.  If you find
errors or other problems with these postings please send corrections
or comments to the posting email address or to the maintainers as
directed in the perlfaq manual page.

Note that the FAQ text posted by this server may have been modified
from that distributed in the stable Perl release.  It may have been
edited to reflect the additions, changes and corrections provided
by respondents, reviewers, and critics to previous postings of
these FAQ. Complete text of these FAQ are available on request.

The perlfaq manual page contains the following copyright notice.

  AUTHOR AND COPYRIGHT

    Copyright (c) 1997-2002 Tom Christiansen and Nathan
    Torkington, and other contributors as noted. All rights 
    reserved.

This posting is provided in the hope that it will be useful but
does not represent a commitment or contract of any kind on the part
of the contributers, authors or their agents.

5.How can pass hash to subroutine ? 

Hi all,

how can we pass hash to subroutine? and retrieving the hash in
subroutine to print values of hash. 


Thanks,
Siva

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