cvs commit: perlfaq perlfaq4.pod

cvsuser     02/09/10 12:49:38

  Modified:    .        perlfaq4.pod
  Log:
  * How do I find the first array element for which a condition is true?
     + added List::Util::first example
     + added foreach example for those without List::Util
     + adjusted for() example to match the other two.
  
  i'm also trying something new - the first sentence of the answer includes
  the question and the answer.
  
  Revision  Changes    Path
  1.32      +31 -10    perlfaq/perlfaq4.pod
  
  Index: perlfaq4.pod
  ===================================================================
  RCS file: /cvs/public/perlfaq/perlfaq4.pod,v
  retrieving revision 1.31
  retrieving revision 1.32
  diff -u -w -r1.31 -r1.32
  --- perlfaq4.pod	4 Sep 2002 22:32:19 -0000	1.31
  +++ perlfaq4.pod	10 Sep 2002 19:49:38 -0000	1.32
  @@ -1,6 +1,6 @@
   =head1 NAME
   
  -perlfaq4 - Data Manipulation ($Revision: 1.31 $, $Date: 2002/09/04 22:32:19 $)
  +perlfaq4 - Data Manipulation ($Revision: 1.32 $, $Date: 2002/09/10 19:49:38 $)
   
   =head1 DESCRIPTION
   
  @@ -1265,16 +1265,37 @@
   
   =head2 How do I find the first array element for which a condition is true?
   
  -You can use this if you care about the index:
  -
  -    for ($i= 0; $i < @array; $i++) {
  -        if ($array[$i] eq "Waldo") {
  -	    $found_index = $i;
  +To find the first array element which satisfies a condition, you can
  +use the first() function in the List::Util module, which comes with
  +Perl 5.8.  This example finds the first element that contains "Perl".
  +
  +	use List::Util qw(first);
  +	
  +	my $element = first { /Perl/ } @array;
  +	
  +If you cannot use List::Util, you can make your own loop to do the
  +same thing.  Once you find the element, you stop the loop with last.
  +
  +	my $found;
  +	foreach my $element ( @array )
  +		{
  +		if( /Perl/ ) { $found = $element; last }
  +		}
  +
  +If you want the array index, you can iterate through the indices
  +and check the array element at each index until you find one
  +that satisfies the condition.
  +
  +	my( $found, $i ) = ( undef, -1 );
  +    for( $i = 0; $i < @array; $i++ ) 
  +    	{
  +        if( $array[$i] =~ /Perl/ ) 
  +        	{ 
  +        	$found = $array[$i];
  +        	$index = $i; 
               last;
           }
       }
  -
  -Now C<$found_index> has what you want.
   
   =head2 How do I handle linked lists?