unexpected RE match


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unexpected RE match

by WoodyWeaver (Monk)

on Jul 05, 2017 at 22:54 UTC ( [id://1194316]=perlquestion: print w/replies, xml )

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WoodyWeaver has asked for the wisdom of the Perl Monks concerning the following question:

I'm parsing time from a last output. I got an unexpected input, so getting an unexpected output shouldn't be surprising, but for the life of me I can't figure out what perl is doing.

subroutine is

sub minutes {
  my $time = shift;
  print "minutes handed $time " if $DEBUG_MINUTES;
  if ( $time =~ /(\d+):(\d+)/ ) {
    print "Interpreted as $1 hours $2 mins\n" if $DEBUG_MINUTES;
    return 60 * $1 + $2;
  } elsif (/(\d+)+(\d+):(\d+)/) {
    print "Interpreted as $1 days, $2 hours, $3 minutes\n" if $DEBUG_M
+INUTES;
    return ( 24 * $1 + $2 ) * 60 + $3;
  } else {
    warn "I don't understand time $time\n";
    return $time;
  }
}
[download]

I was processing a line

archerh                                Thu Jun 22 10:25 - down  (-6+-1
+2:-52)
[download]

and I get

minutes handed -6+-12:-52 Interpreted as 1 days, 0 hours, 25 minutes
[download]

How does \d+ do this?

Comment on unexpected RE match Select or Download Code

Replies are listed 'Best First'.
Re: unexpected RE match by Anonymous Monk on Jul 05, 2017 at 23:01 UTC
`elsif (/(\d+)+(\d+):(\d+)/)` matches against `$_` because you forgot to say `elsif ( $time =~ /(\d+)+(\d+):(\d+)/ )`, and `$_` is probably the whole input line, and `use Data::Dumper; print Dumper( "Thu Jun 22 10:25" =~ /(\d+)+(\d+):(\d+)/ ); __END__ $VAR1 = '1'; $VAR2 = '0'; $VAR3 = '25';` [download]	[reply] [d/l] [select]
Re^2: unexpected RE match by WoodyWeaver (Monk) on Jul 05, 2017 at 23:05 UTC
many thanks. we always see what we expect, not what is there.	[reply]
Re^3: unexpected RE match by Anonymous Monk on Jul 07, 2017 at 01:42 UTC
Also note that your regex isn't going to match those minus signs. -G	[reply]
Re^3: unexpected RE match by Anonymous Monk on Jul 06, 2017 at 22:43 UTC
PerlMonks iz awe-some. I love the vibe.	[reply]

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