Hi,

I came around this old code of mine: 

# Get the n-th or innermost (if n = -1) argument of
# property. Empty string if property isn't parametrized
sub get_proparg {
  my $propstr = shift;         # get the property string
  my $level   = shift || 0;    # get the level we want to extract
  my $back    = $propstr;      # Initialize Return value (for case lev
+el=0)
  my $cnt;                     # initialize counter

  if($level == -1) {           # special case, get the innermost argum
+ent
    $propstr =~ /\(([^\(\)]+)\)+/;
    $propstr = $1;
  } else {                     # get whatever argument $level indicate
+s
    for($cnt = 0;$cnt<$level; $cnt++) {
      $propstr =~ /\((.+)\)/;
      $propstr = $1;
    }
  }

  return $propstr;
}

[download]
What it basically does is to remove a properties outer peeling like an onion: ;-) 
"hello(what(is(this(all(about)))))" 0
get_proparg returned: >>hello(what(is(this(all(about)))))<<
"hello(what(is(this(all(about)))))" 1
get_proparg returned: >>what(is(this(all(about))))<<
"hello(what(is(this(all(about)))))" 2
get_proparg returned: >>is(this(all(about)))<<
"hello(what(is(this(all(about)))))" 3
get_proparg returned: >>this(all(about))<<
"hello(what(is(this(all(about)))))" 4
get_proparg returned: >>all(about)<<
"hello(what(is(this(all(about)))))" 5
get_proparg returned: >>about<<
"hello(what(is(this(all(about)))))" -1
get_proparg returned: >>about<<
As this code happens to be time critical I came around and tried to refactor it. The biggest culprit seems to be the iterative for loop which is of course linear with the number of levels we have to descend. We may surely assume that the parentheses are balanced. But unfortunatedly the mightyness of Regexps doesn't cover "balanced parentheses matching".

Anyone a suggestion how to get rid of the loop?

Bye
 PetaMem     All Perl:   MT, NLP, NLU

In reply to Peeling the Peelings by PetaMem

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