4.6. Iterating Over an Array by Reference4.6.1. ProblemYou have a reference to an array, and you want to use a loop to work with the array's elements. 4.6.2. SolutionUse foreach or for to loop over the dereferenced array: # iterate over elements of array in $ARRAYREF foreach $item (@$ARRAYREF) { # do something with $item } for ($i = 0; $i <= $#$ARRAYREF; $i++) { # do something with $ARRAYREF->[$i] } 4.6.3. DiscussionThe solutions assume you have a scalar variable containing the array reference. This lets you do things like this: @fruits = ( "Apple", "Blackberry" ); $fruit_ref = \@fruits; foreach $fruit (@$fruit_ref) { print "$fruit tastes good in a pie.\n"; } Apple tastes good in a pie. Blackberry tastes good in a pie. We could have rewritten the foreach loop as a for loop like this: for ($i=0; $i <= $#$fruit_ref; $i++) { print "$fruit_ref->[$i] tastes good in a pie.\n"; } Frequently, though, the array reference is the result of a more complex expression. Use the @{ EXPR } notation to turn the result of the expression back into an array: $namelist{felines} = \@rogue_cats; foreach $cat ( @{ $namelist{felines} } ) { print "$cat purrs hypnotically..\n"; } print "--More--\nYou are controlled.\n"; Again, we can replace the foreach with a for loop: for ($i=0; $i <= $#{ $namelist{felines} }; $i++) { print "$namelist{felines}[$i] purrs hypnotically.\n"; } 4.6.4. See Alsoperlref(1) and perllol(1); Chapter 8 of Programming Perl; Recipe 11.1; Recipe 4.5 Copyright © 2003 O'Reilly & Associates. All rights reserved. |
|