Thu_Feb__7_15:01:28_PST_2019

Perl - Arrays Advertisements Previous Page Next Page ï¿‚ï¾  An array is a variable that stores an ordered list of scalar values. Array variables are preceded by an "at" (@) sign. To refer to a single element of an array, you will use the dollar sign ($) with the variable name followed by the index of the element in square brackets. Here is a simple example of using the array variables ￢ﾈï¾' Live Demo #!/usr/bin/perl @ages = (25, 30, 40); @names = ("John Paul", "Lisa", "Kumar"); print "\$ages[0] = $ages[0]\n"; print "\$ages[1] = $ages[1]\n"; print "\$ages[2] = $ages[2]\n"; print "\$names[0] = $names[0]\n"; print "\$names[1] = $names[1]\n"; print "\$names[2] = $names[2]\n"; Here we have used the escape sign (\) before the $ sign just to print it. Other Perl will understand it as a variable and will print its value. When executed, this will produce the following result ￢ﾈï¾' $ages[0] = 25 $ages[1] = 30 $ages[2] = 40 $names[0] = John Paul $names[1] = Lisa $names[2] = Kumar In Perl, List and Array terms are often used as if they're interchangeable. But the list is the data, and the array is the variable. Array Creation Array variables are prefixed with the @ sign and are populated using either parentheses or the qw operator. For example ￢ﾈï¾' @array = (1, 2, 'Hello'); @array = qw/This is an array/; The second line uses the qw// operator, which returns a list of strings, separating the delimited string by white space. In this example, this leads to a four-element array; the first element is 'this' and last (fourth) is 'array'. This means that you can use different lines as follows ￢ﾈï¾' @days = qw/Monday Tuesday ... Sunday/; You can also populate an array by assigning each value individually as follows ￢ﾈï¾' $array[0] = 'Monday'; ... $array[6] = 'Sunday'; Accessing Array Elements When accessing individual elements from an array, you must prefix the variable with a dollar sign ($) and then append the element index within the square brackets after the name of the variable. For example ￢ﾈï¾' Live Demo #!/usr/bin/perl @days = qw/Mon Tue Wed Thu Fri Sat Sun/; print "$days[0]\n"; print "$days[1]\n"; print "$days[2]\n"; print "$days[6]\n"; print "$days[-1]\n"; print "$days[-7]\n"; This will produce the following result ￢ﾈï¾' Mon Tue Wed Sun Sun Mon Array indices start from zero, so to access the first element you need to give 0 as indices. You can also give a negative index, in which case you select the element from the end, rather than the beginning, of the array. This means the following ￢ﾈï¾' print $days[-1]; # outputs Sun print $days[-7]; # outputs Mon Sequential Number Arrays Perl offers a shortcut for sequential numbers and letters. Rather than typing out each element when counting to 100 for example, we can do something like as follows ￢ﾈï¾' Live Demo #!/usr/bin/perl @var_10 = (1..10); @var_20 = (10..20); @var_abc = (a..z); print "@var_10\n"; # Prints number from 1 to 10 print "@var_20\n"; # Prints number from 10 to 20 print "@var_abc\n"; # Prints number from a to z Here double dot (..) is called range operator. This will produce the following result ￢ﾈï¾' 1 2 3 4 5 6 7 8 9 10 10 11 12 13 14 15 16 17 18 19 20 a b c d e f g h i j k l m n o p q r s t u v w x y z Array Size The size of an array can be determined using the scalar context on the array - the returned value will be the number of elements in the array ￢ﾈï¾' @array = (1,2,3); print "Size: ",scalar @array,"\n"; The value returned will always be the physical size of the array, not the number of valid elements. You can demonstrate this, and the difference between scalar @array and $#array, using this fragment is as follows ￢ﾈï¾' Live Demo #!/usr/bin/perl @array = (1,2,3); $array[50] = 4; $size = @array; $max_index = $#array; print "Size: $size\n"; print "Max Index: $max_index\n"; This will produce the following result ￢ﾈï¾' Size: 51 Max Index: 50 There are only four elements in the array that contains information, but the array is 51 elements long, with a highest index of 50. Adding and Removing Elements in Array Perl provides a number of useful functions to add and remove elements in an array. You may have a question what is a function? So far you have used print function to print various values. Similarly there are various other functions or sometime called sub-routines, which can be used for various other functionalities. Sr.No. Types