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(tye)Re: GOTO considered (a necessary) evil?

by tye (Cardinal)
on Jul 15, 2002 at 15:43 UTC ( #181826=note: print w/ replies, xml ) Need Help??


in reply to GOTO considered (a necessary) evil?

My favorite way to refactor loops that have the conditional in the middle is to use a subroutine because return in the middle of a subroutine seems an easy thing to understand (and to notice) when you come back to the code. It also avoids arguments with people who can't handle goto.

I also prefer to force eval to return a true value when it succeeds rather than checking $@ since there are cases where $@ can give the wrong impression about whether the eval was successful.

sub tieSession { while( 1 ) { if( eval { tie %session, 'Apache::Session::MySQL', $session, { Handle => HH::DB->db_Main, LockHandle => HH::DB->db_Main }; 1; } ) { return; } if( $@ !~ /^Object does not exist/ ) { print $cgi->header; die_nice( 'Database Error', 'Unable to connect at this time' ); } undef $session; } }
So I don't consider goto inherently evil. I prefer your original code over your coworkers in at least some respects. I really hate the use of Perl bare blocks as loops and think it often leads to more spagetti code than even goto does (expecting people to notice a "redo" burried so deep inside in order to realize that a loop was suddenly created out of a bare block).

But I wouldn't over golf for "excellence". Is the code working? There is probably something more important to be working on. (:

        - tye (but my friends call me "Tye")


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Re: (tye)Re: GOTO considered (a necessary) evil?
by RMGir (Prior) on Jul 15, 2002 at 16:26 UTC
    It also avoids arguments with people who can't handle goto.

    I'd agree with you, except I ran into at least one developer who thought that returns from the middle of subroutines were just as unreasonable as goto's. :)

    I'm in the "if I can understand what it's doing, it's fine" camp, myself. The goto in the original message was pretty clear, as is your example.
    --
    Mike

        You seem to have misunderstood my position...

        I wasn't saying they were bad, I was just saying I'd worked with someone who thought
        a) goto's BAD, no exceptions
        b) return from middle of subroutine == goto.

        That's NOT my position at all. I believe in _necessary_ gotos, and don't mind return/redo/last/next at all, as long as they're not used to cause chaos :)
        --
        Mike

Re: (tye)Re: GOTO considered (a necessary) evil?
by Anonymous Monk on Jul 15, 2002 at 19:40 UTC
    there are cases where $@ can give the wrong impression about whether the eval was successful.

    Can you give an example of that?

      Sure:

      sub DESTROY { eval "1" } eval 'my $x = bless {}; die "ouch\n"'; print "($@)\n";
      which prints "()" not "(ouch\n)".

              - tye (but my friends call me "Tye")

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