Perl map to Avoid Code Repetition
I see new developers often having difficulties in understanding how operators likemap can be useful.
While it is true that map can be useful to transform an array into another array, remapping the former into the latter, the map can be used also to automate the same code over and over.
Imagine you need to extract a set of values calling the same method with different parameters:
my $a = $xml->getTag( 'a' );
my $b = $xml->getTag( 'b' );
my $c = $xml->getTag( 'c' );
Perl support mutiple assignments, so the above can be rewritten as:
my ( $a, $b, $c ) = ( $xml->getTag( 'a' ),
$xml->getTag( 'b' ),
$xml->getTag( 'c' ) );
The above is the first step towards using
map to evolve the above boring code:
my ( $a, $b, $c ) = map { $xml->getTag( $_ ) }
qw/ a b c /;
Note how in the above piece of code, there is a single call to the method, while the work is repeated by the
map operator that will invoke the method for every word in the qw (quote word) operator. The calls (return value) are then placed into a list, that is in turn assigned to variables.