in reply to Re: Perl's Bad Ideas
in thread Perl's Bad Ideas

See, it almost makes sense, but I'm not satisfied.

If there were a comma after the filehandle, then what would this do? print $x, $y; Are you printing the contents of $y to filehandle $x? Or are you printing the contents of $x and $y to stdout?
If $x is a filehandle, of course I am printing contents of $y to filehandle $x.

Your other alternative is a non-alternative. If $x is a filehandle, print $x, $y; doesn't print contents of $x and $y to STDOUT, it generates error 'No comma allowed after filehandle...'.

So if it's not really a choice, why not 'do the right thing'.

If Perl is smart enough to know it's a filehandle, why isn't it smart enough to use it as such?

YuckFoo

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Re: Perl's Bad Ideas
by Dominus (Parson) on Apr 07, 2002 at 00:00 UTC
    Says YuckFoo:
    If $x is a filehandle, of course I am printing contents of $y to filehandle $x.
    You seem to have missed the point here. That's probably my fault.

    You said "If $x is a filehandle...". How can you tell if $x is a filehandle? (Answer: You can't.)

    If Perl is smart enough to know it's a filehandle, why isn't it smart enough to use it as such?
    Perl doesn't have any magic way to know it's a filehandle. That's why you have to leave off the comma. The missing comma says "By the way, this is a filehandle."

    Let's try a slightly more concrete example:

        $x = 'STDERR';
    $y = "I like pie.\n"
    print $x, $y;

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    Now what?

    --
    Mark Dominus
    Perl Paraphernalia

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      It would have seemed to me the obvious behavior is to 
      print 'STDERR', "I like pie.\n";

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      to STDOUT. *However* fileno($x) returns 2. How uncool is that? I suppose you could ignore the cases where 
      grep {$x eq $_ } 'STDIN', 'STDOUT', 'STDERR'

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      And in all other cases you check fileno($x).

      --
      perl -pe "s/\b;([st])/'\1/mg"

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        Says belg4mit:
        It would have seemed to me the obvious behavior is to 
          print 'STDERR', "I like pie.\n";

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        to STDOUT.
        Oh. So you're saying that there is no way to store a filehandle in a variable then. (Or at least, once you have, you can no longer print to it.) That seems to me like a somewhat bigger defect than having to omit a comma once in a while, but hey, if you say it's "obvious"...

        fileno($x) returns 2. How uncool is that?
        Well, of course it does. What did you think fileno STDERR was doing, anyway? STDERR is a bareword. You know what barewords do. fileno STDERR is the same as fileno 'STDERR' which is the same as fileno $x because $x contains STDERR.
        I suppose you could ignore the cases where 
          grep {$x eq $_ } 'STDIN', 'STDOUT', 'STDERR'

        [download]
        And in all other cases you check fileno($x).
        That makes no sense at all. You can't just 'ignore' the STDERR case; you have to do something. If you treat "STDERR" as a filehandle, it means you can't print the string STDERR to the standard output, which is a pretty serious defect. If you treat it as a string, it means you can't print anything to standard error. I don't think either of those is a very good choice.

        In other cases, you want to check fileno. Well, let's see what happens if you do that.

            sub foo {
      my ($code, $serial, $location) = @_;
      print "X", $code, "-", $serial, ": $location\n";
    }

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        This function works just fine, printing to stdout, until one day you forget and open a filehandle named X in some completely separate part of the program, and then suddenly the function is printing to filehandle X instead of to standard output. I don't think that was a very good choice either.

        Face it, if Larry had done anything as foolish as what you suggest, you guys wouldhave a lot more cause for complaint than you do with the missing comma.

        --
        Mark Dominus
        Perl Paraphernalia

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In Section Meditations