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Re: Flip-flop reset?

by ysth (Canon)
on Aug 30, 2006 at 21:56 UTC ( [id://570490]=note: print w/replies, xml ) Need Help??


in reply to Flip-flop reset?

my @arr = ...;
sub mySub {
  goto &{ sub {  # added line
    foreach ( @arr ) {
      if ( /^PIDTAB/ ... /^\n/ ) {
        next if ( /^(PIDTAB|\n)/ );

        while ( /\s+(\d+):\s+(\d+)\s*:\S+:\S+:D\s+/g ) {
           # do something
        }
      }
    }
  }}  # added line
}

[download]
will do the trick, since the sub {} will get a new pad (where the .. state is stored) each time mySub is called. This only works if the sub is a closure (uses an outer lexical); otherwise, the sub{} is treated more as if it were a kind of constant, and doesn't get a new pad each time the reference is returned by sub. If @arr isn't lexical, you can still force a closure by replacing 
goto &{ sub {

[download]
with 
my $dummy; goto &{ sub { $dummy if 0;

[download]

Replies are listed 'Best First'.
Re^2: Flip-flop reset?
by runrig (Abbot) on May 31, 2007 at 23:12 UTC
    I was recently wondering how to do this, and why a regular anonymous sub (w/o closures) wouldn't work. Then I found this node. Though my solution (before finding this) was to generate an anonymous sub using eval $string. E.g.
    
my $range_checker = eval 'sub { local $_ = shift; /foo/../bar/ }';

    [download]
    At first, your way seems a little too indirect and magical, but it makes perfect sense if you create a 'flip-flop generator':
    
sub mk_flip_flop {
  my ( $re1, $re2 ) = @_;
  sub { local $_ = shift; /$re1/../$re2/ }
}

    [download]
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Re^2: Flip-flop reset?
by ysth (Canon) on Aug 31, 2006 at 21:07 UTC
    I was thinking, local $.; has the odd, but documented, effect of localizing the last-read-filehandle. Maybe it could be extended to localize the state of ../... too. :)
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