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Programming Scripts Articles
Page 20 of 33
Perl 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 −Example#!/usr/bin/perl @var_10 = (1..10); @var_20 = (10..20); @var_abc = (a..z); print "@var_10"; # Prints number from 1 to 10 print "@var_20"; # Prints number from 10 to 20 print "@var_abc"; # Prints number from a to zHere double dot (..) is called range operator. This will produce the following result −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
Read MoreArray Size in Perl
The size of an array in Perl can be determined using the scalar context on the array - the returned value will be the number of elements in the array −@array = (1, 2, 3); print "Size: ", scalar @array, "";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 −Example#!/usr/bin/perl @array = (1, 2, 3); $array[50] = 4; $size = @array; $max_index = $#array; print "Size: $size"; print "Max Index: $max_index";OutputThis will ...
Read MoreAdding and Removing Elements in Perl 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 the print function to print various values. Similarly, there are various other functions or sometimes called subroutines, which can be used for various other functionalities.Sr.No.Types & Description1push @ARRAY, LISTPushes the values of the list onto the end of the array.2pop @ARRAYPops off and returns the last value of the array.3shift @ARRAYShifts the first value of the array off and returns it, shortening the array by 1 and moving everything down.4unshift @ARRAY, ...
Read MoreSlicing Array Elements in Perl
You can also extract a "slice" from an array - that is, you can select more than one item from an array in order to produce another array.Example#!/usr/bin/perl @days = qw/Mon Tue Wed Thu Fri Sat Sun/; @weekdays = @days[3, 4, 5]; print "@weekdays";OutputThis will produce the following result −Thu Fri SatThe specification for a slice must have a list of valid indices, either positive or negative, each separated by a comma. For speed, you can also use the .. range operator −Example#!/usr/bin/perl @days = qw/Mon Tue Wed Thu Fri Sat Sun/; @weekdays = @days[3..5]; print "@weekdays";OutputThis will produce the ...
Read MoreReplacing Array Elements in Perl
Now we are going to introduce one more function called splice(), which has the following syntax −Syntaxsplice @ARRAY, OFFSET [ , LENGTH [ , LIST ] ]This function will remove the elements of @ARRAY designated by OFFSET and LENGTH, and replaces them with LIST if specified. Finally, it returns the elements removed from the array. Following is the example −Example#!/usr/bin/perl @nums = (1..20); print "Before - @nums"; splice(@nums, 5, 5, 21..25); print "After - @nums";OutputThis will produce the following result −Before - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ...
Read MoreTransform Perl Arrays to Strings
We can use the join() function in Perl to rejoin the array elements and form one long scalar string. This function has the following syntax −Syntaxjoin EXPR, LISTThis function joins the separate strings of LIST into a single string with fields separated by the value of EXPR and returns the string. Following is the example −Example#!/usr/bin/perl # define Strings $var_string = "Rain-Drops-On-Roses-And-Whiskers-On-Kittens"; $var_names = "Larry, David, Roger, Ken, Michael, Tom"; # transform above strings into arrays. @string = split('-', $var_string); @names = split(', ', $var_names); $string1 = join( '-', @string ); $string2 = join( ', ', @names ); ...
Read MoreSorting Arrays in Perl
The sort() function in Perl sorts each element of an array according to the ASCII Numeric standards. This function has the following syntax −Syntaxsort [ SUBROUTINE ] LISTThis function sorts the LIST and returns the sorted array value. If SUBROUTINE is specified then specified logic inside the SUBROUTINE is applied while sorting the elements.Example#!/usr/bin/perl # define an array @foods = qw(pizza steak chicken burgers); print "Before: @foods"; # sort this array @foods = sort(@foods); print "After: @foods";OutputThis will produce the following result −Before: pizza steak chicken burgers After: burgers chicken pizza steakPlease note that sorting is performed based on the ...
Read MoreThe $[ Special Variable in Perl
Perl provides numerous special variables, which have their predefined meaning.We have a special variable, which is written as $[. This special variable is a scalar containing the first index of all arrays. Because Perl arrays have zero-based indexing, $[ will almost always be 0. But if you set $[ to 1 then all your arrays will use on-based indexing. It is recommended not to use any other indexing other than zero. However, let's take one example to show the usage of $[ variable −Example#!/usr/bin/perl # define an array @foods = qw(pizza steak chicken burgers); print "Foods: @foods"; # Let's reset ...
Read MoreMerging Arrays in Perl
Because an array in Perl is just a comma-separated sequence of values, you can combine them together as shown below −Example#!/usr/bin/perl @numbers = (1,3,(4,5,6)); print "numbers = @numbers";OutputThis will produce the following result −numbers = 1 3 4 5 6The embedded arrays just become a part of the main array as shown below −Example#!/usr/bin/perl @odd = (1,3,5); @even = (2, 4, 6); @numbers = (@odd, @even); print "numbers = @numbers";OutputThis will produce the following result −numbers = 1 3 5 2 4 6
Read MoreSelecting Elements from Lists in Perl
The list notation in Perl is identical to that for arrays. You can extract an element from an array by appending square brackets to the list and giving one or more indices −Example#!/usr/bin/perl $var = (5,4,3,2,1)[4]; print "value of var = $var"OutputThis will produce the following result −value of var = 1Similarly, we can extract slices, although without the requirement for a leading @ character −Example#!/usr/bin/perl @list = (5,4,3,2,1)[1..3]; print "Value of list = @list";OutputThis will produce the following result −Value of list = 4 3 2
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