cvs commit: perlfaq perlfaq4.pod

cvsuser     02/05/16 05:44:24

  Modified:    .        perlfaq4.pod
  Log:
  ==> How do I process/modify each element of an array?
  
  * updated comment about values() making a copy within the
  foreach context (new as of 5.6.x)
  
  ==> How do I manipulate arrays of bits?
  
  * added another example from Benjamin Goldberg
  
  Revision  Changes    Path
  1.22      +19 -5     perlfaq/perlfaq4.pod
  
  Index: perlfaq4.pod
  ===================================================================
  RCS file: /cvs/public/perlfaq/perlfaq4.pod,v
  retrieving revision 1.21
  retrieving revision 1.22
  diff -u -w -r1.21 -r1.22
  --- perlfaq4.pod	6 May 2002 13:08:46 -0000	1.21
  +++ perlfaq4.pod	16 May 2002 12:44:24 -0000	1.22
  @@ -1,6 +1,6 @@
   =head1 NAME
   
  -perlfaq4 - Data Manipulation ($Revision: 1.21 $, $Date: 2002/05/06 13:08:46 $)
  +perlfaq4 - Data Manipulation ($Revision: 1.22 $, $Date: 2002/05/16 12:44:24 $)
   
   =head1 DESCRIPTION
   
  @@ -1396,13 +1396,20 @@
   	$_ *= (4/3) * 3.14159;  # this will be constant folded
       }
   
  -If you want to do the same thing to modify the values of the hash,
  -you may not use the C<values> function, oddly enough.  You need a slice:
  +If you want to do the same thing to modify the values of the
  +hash, you can use the C<values> function.  As of Perl 5.6
  +the values are not copied, so if you modify $orbit (in this
  +case), you modify the value.
   
  -    for $orbit ( @orbits{keys %orbits} ) {
  +    for $orbit ( values %orbits ) {
   	($orbit **= 3) *= (4/3) * 3.14159; 
       }
   
  +Prior to perl 5.6 C<values> returned copies of the values,
  +so older perl code often contains constructions such as
  +C<@orbits{keys %orbits}> instead of C<values %orbits> where
  +the hash is to be modified.
  +    
   =head2 How do I select a random element from an array?
   
   Use the rand() function (see L<perlfunc/rand>):
  @@ -1539,6 +1546,13 @@
   
   This method gets faster the more sparse the bit vector is.
   (Courtesy of Tim Bunce and Winfried Koenig.)
  +
  +You can make the while loop a lot shorter with this suggestion
  +from Benjamin Goldberg:
  +
  +	while($vec =~ /[^\0]+/g ) {
  +	   push @ints, grep vec($vec, $_, 1), $-[0] * 8 .. $+[0] * 8;
  +	}
   
   Or use the CPAN module Bit::Vector: