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Re (tilly) 3 (comments): Supersplit

by tilly (Archbishop)
on Jan 01, 2001 at 00:50 UTC ( #49124=note: print w/ replies, xml ) Need Help??


in reply to Re: Re (tilly) 1: Supersplit
in thread Supersplit

Here is explanation for my feedback:

  1. Why reverse the order for the arguments? join and split both first start with the separator, and than the input. So I changed the order back to strings, input.

    Because if you have positionally determined arguments with one list being variable length, it is usual to have the variable list at the end of your argument list. In this case when I made it recursive (and therefore capable of handling n-dim arrays) you had a variable length list of things to join and split. So I moved those arguments to the end.

  2. I don't like to pre-compile the regex's, otherwise the split couldn't cope with changing delimiters, as in a text file (see the SYNOPSIS), or with sprintf'ed data. So I changed that back. Furthermore, I couldn't find any reference to qr// in manpages. Could you please explain?

    Pre-compiling the regexes should not pose a problem for having patterns that handle multiple delimiters. Could you try it and report back? As for documents, the docs on this server are 5.003 specific. (Same as Camel 2.) Most people are on 5.005 or 5.6. On those machines you can find out about the feature from the local documentation using the perldoc utility. In fact in this case: perldoc -f qr directs you to perlop/"Regexp Quote-Like Operators". So try perldoc perlop and then type /Quote-Like to get to the relevant section. Then /qr and hit 'n' until you get to the right spot. (The same search/paging tricks work with utilities like man and less on *nix systems.)

  3. ...more dimensional arrays are a perl 5 feature, so I should check for that anyway. Out of time now, so next version of supersplit.

    I already did that with the recursion. :-)

  4. I really like the recursive approach.

    So did I. :-)

  5. I don't see the need for a separate IO version, so I changed that back, too. I just try to treat the string as a filehandle, or try to open it as file (new feature). I didn't succeed to get supersplit( INPUT ), with INPUT as a filehandle, to work. That's peculiar, because the manpage tells me that <$fh$gt;, with $fh='INPUT', should work.

    The need is due to your having overloaded the input too much. For instance if someone tried to use your current version of supersplit() on an uploaded file from CGI they would fail miserably. I also really don't like trying an open and silently failing.

    Additionally it is generally a bad idea to limit how your caller can pass information. What if I really want to pass you data from a socket? Or from IO::Scalar? Or from a string I have already pre-processed? Having two functions, one of which is a wrapper around the other, for that situation leaves you with a consistent interface and more flexibility.

    As for your comment on what you are surprised is failing, I would not expect that to work. Which manpage led you to expect that it would?

  6. You are totally right on the matter of the inner/outer naming convention.

    Get bitten often enough and you become sensitive to potential confusions in names. :-)

    The real issue here is the same one which makes it hard for programmers to find their own bugs. You need to step out of your own pre-conceptions of how you are supposed to be working and thinking and see the problem from what another person's PoV is likely to be. This is frequently much easier for another person to do...

  7. And ++ for the join( $_, @_) stuff. I never would have dared to use it. But of course $_ and @_ have different namespaces..

    :-)

  8. I I removed the BEGIN blocks. Is this something for the manpages (perldoc perlmod)?

    Well it is something that I know because I looked in some detail at Carp and Exporter a while ago. While the principles of what happens when are documented, I don't think that the conclusion is stated anywhere. I certainly had to learn it by reading and thinking through the code.


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Re: Re (tilly) 3 (comments): Supersplit
by jeroenes (Priest) on Jan 02, 2001 at 04:26 UTC
    I have to ponder this for a while, and my time for perl is limited at the moment. But for the time being I will like to go into more detail about the filehandle stuff. I read CGI, and I understand the problem, because returns a variable containing both name and filehandle. I would guess that a check for reference should avoid this problem.

    My assumption about the workings of $fh='INPUT'; join '',<$fh>; are based on perldoc:perlop, saying 'If the string inside the angle brackets is a reference to a scalar variable (e.g., <$foo>), then that variable contains the name of the filehandle to input from, or a reference to the same.'.

    I understand the argument about the pipe and stuff, and I think a open.. "$fh" || open .. "<$fh" should do the trick here. I don't have IO::Scalar here, I'll ponder that later.

    You worry about a trying open and silently failing. Well, I tried it, and the code simply returns the name if the open failed (and there is nothing to split on) as the first element. That leaves room for a check.

    Furthermore, the code returns a prepared string as well, if reading as a filehandle fails. I quickly glanced at IO::Scalar, and I think the ref check should allow that as well. I think the following code should work.

    sub _text{ my $fh = shift; unless (defined($fh)) { $fh = \*STDIN; } if ( (! ref $fh) && ((open INPUT, "$fh") || open INPUT, "<$fh" )) +{ $fh = join '', <INPUT>; close INPUT; } no strict 'refs'; (join '', <$fh>) || $fh; }

    Bye,

    Jeroen
    I was dreaming of guitarnotes that would irritate an executive kind of guy (FZ)

Re: Re (tilly) 3 (comments): Supersplit
by jeroenes (Priest) on Jan 02, 2001 at 18:31 UTC
    After some CB discussion, tilly convinced me why the open was not such good magic. So I devoted a separate routine to that. The filehandle still is in the normal supersplit routine.

    I personally vote for the split order of arguments, because people are more familiar with that. I think the variable length list can be coped with by the pop's. If that's unusual, so be it. I know that this order is mostly not a good idea.

    Moreover, you can provide a limit option now. Because there is some magic involved, I doubled a function that doesn't try to find a limit parameter at the end.

    The code has been posted more than enough now, so I hooked it up to my homenode. POD has been updated. Code has been tested.

    Cheers,

    Jeroen
    I was dreaming of guitarnotes that would irritate an executive kind of guy (FZ)

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