Arrays are ordered collections of zero or more scalar values, indexed by position. An array
variable begins with the at sign @
followed by a
legal variable name. For instance, here are two possible array variable
names:
@array1 @dna_fragments
You can assign scalar values to an array by placing the scalar values in a list, separated by commas and surrounded by a pair of parentheses. For instance, you can assign an array the empty list:
@array = ( );
or one or more scalar values:
@dna_fragments = ('ACGT', $fragment2, 'GGCGGA'),
Notice that it's okay to specify a scalar variable such as $fragment2
in a list. Its current value, not the
variable name, is placed into the array.
The individual scalar values of an array (the elements) are
indexed by their position in the array. The index numbers begin at 0.
You can specify the individual elements of an array by preceding the array name by a $
and following it with the index number of the
element within square brackets [ ]
, like
so:
$dna_fragments[2]
This equals the value of 'GGCGGA'
, given the
values previously set for this array. Notice that the array has three scalar values,
indexed by numbers 0, 1, and 2. The third and last element is indexed 2, one less
than the total number of elements 3, because the first element is indexed number
0.
You can make a copy of an array using an assignment operator =
, as in this example that makes a copy @output
of an existing array @input
:
@output = @input;
If you evaluate an array in scalar context, the value is the number of elements in the array. So if
array @input
has five elements, the following
example assigns the value 5 to $count
:
$count = @input;
Figure B-1 shows an array @myarray
with three elements, which demonstrates the
ordered nature of an array; by which each element appears, and can be found by its
position in the array.