PERL/C2/Array-functions/English

Title Of Script: Array functions in Perl

Author: Amol Brahmankar

Keywords: Array functions in perl video tutorial.

Visual Cue	Narration
Slide	Welcome to the spoken tutorial on Array Functions in Perl
Slide: Learning Objectives	In this tutorial, we will learn about Array functions in Perl, like push pop shift unshift split splice join sort qw
Slide: System Requirements	I am using Ubuntu Linux12.04 operating system and Perl 5.14.2 I will also be using the gedit Text Editor. You can use any text editor of your choice.
Slide: Prerequisites	You should have basic knowledge of Variables, Data Structures & Arrays in Perl Knowledge of Comments, loops and conditional statements will be an added advantage. Please go through the relevant spoken tutorials on the spoken tutorial website.
Slide	Perl provides certain inbuilt functions. These functions can perform various operations on an Array.
Slide	Let us first learn how to add and remove elements from last position of an Array. This can be done by using; push function which adds an element at the last position of an Array pop function which removes an element from the last position of an Array
Terminal	Let us understand push and pop functions by using a sample program. Open the terminal and type gedit perlArray dot pl space ampersand Press Enter
Gedit #!/usr/bin/perl @myArray = (1, 2, 3); print "Original array: @myArray\n"; # Insert an element at the last position of an array push (@myArray, 4); print "New array after pushing 4 into an array: @myArray\n"; # Remove an element from the last position of an array pop (@myArray); print "New array after popping element: @myArray\n";	This will open perlArray dot pl file in gedit. Type the code as shown on the screen <<pause>> Here, we have defined an Array of length 3. push function will insert an element at the last position of this Array i.e after 3; whereas, pop function will remove an element from the last position of the Array. In our case, 4 will be removed from the Array.
	Press Ctrl + S to save the file.
Slide	push function takes 2 arguments- 1st argument to the push function, is the Array in which to add an element. 2nd argument is the element which is to be pushed into the Array.
Slide	The syntax of pop function is as follows - pop function takes only one argument It is the Array from which an element needs to be removed.
Slide	Note: Both these functions work at last position of an Array.
Slide	The element removed by pop function can be collected into another variable. The syntax for this is - $variable = pop(@myArray)
Switch to terminal perl perlArray.pl	Now switch to the terminal and execute the Perl script. Type perl perlArray dot pl and press Enter.
Highlight the output on the terminal Original array: 1 2 3 New array after pushing 4 into an array: 1 2 3 4 New array after popping element: 1 2 3	The output is shown on the terminal. Original array New array after pushing 4 into an array New array after popping element
Slide	Now, let us see how to add/remove an element from the 1st position of an Array. This can be achieved using- unshift function - which adds an element to an Array at the 1st position shift function - which removes the first element from an Array.
Gedit	Let us understand this using a sample program. I will open perlArray dot pl file which I have already created.
Gedit # Insert an element at the first position of an array unshift (@myArray, 0); print "Array after adding 0 into an array at 1st position: @myArray\n"; # Remove an element from the first position of an array shift (@myArray); print "Array after removing element from 1st position: @myArray\n";	Type the following piece of code as shown on the screen. unshift function will insert an element at the first position i.e before 1 shift function will remove an element from the first position. In our case, zero will be removed.
	Press Ctrl + S to save the file.
Slide	The unshift function takes 2 arguments - 1st argument is the Array in which to add an element 2nd argument is the element to be added into the Array
Slide	shift function takes only one argument - This is the Array from which the element needs to be removed.
Slide	Note: Both these functions works at first position of an Array.
Slide	We can collect the element removed by shift function into some variable. This syntax for this is - $variable = shift(@myArray)
Switch to terminal perl perlArray.pl	Then switch to the terminal and execute the Perl script. Type perl perlArray dot pl and press Enter.
Highlight the output on the terminal Array after adding 0 into an array at 1st position: 0 1 2 3 Array after removing element from 1st position: 1 2 3	The output displayed on the terminal is as highlighted.
	Now, let us see how to remove an element from a specified position of an Array.
slide	splice function removes an element from a specified position of an Array. The return value of this function is an Array of removed elements.
Gedit	Let us understand this using a sample program. Go to the perlArray dot pl file, which we created earlier.
# Removes element(s) from the specified position @myNewArray = (1, 2, 3, 4, 5, 6, 7, 8, 9); @splicedArray = splice(@myNewArray, 4, 2); print "Spliced Array: @splicedArray\n";	Type the piece of code shown on the screen. We need to provide the index from where we want to remove the elements and the offset upto which we want to remove the elements In our case, the elements 5 and 6 will be removed.
Switch to terminal perl perlArray.pl	Then switch to the terminal and execute the Perl script by typing - perl perlArray dot pl and press Enter.
Highlight the output on the terminal Spliced Array: 5 6	The output displayed on the terminal is as highlighted.
	Now let us look at few other inbuilt functions of Arrays.
Slide	* split function is used to divide a string at a specified delimiter. The return value of this function is an Array. The elements of this Array are the divided portions of the string.
Slide	join function joins the elements of an Array, using the specified delimiter. It returns a string of joined elements.
Slide	sort function sorts an Array in alphabetical/numerical order.
Slide	qw function returns an Array of words, separated by a white space.
	Now let us understand all these functions using a sample program.
Terminal gedit arrayFunctions.pl &	Switch to terminal and type gedit arrayFunctions dot pl space ampersand
Gedit #!/usr/bin/perl use Data::Dumper; $string = "Illustration Of Array Functions"; @newArray = split (/ /, $string); print "Declared String: $string\n\n"; print "Array after split: \n"; print Dumper \@newArray; print "\n"; $joinedString = join(", ", @newArray); print "String After Join: $joinedString\n\n"; @sortedArray = sort(@newArray); print "Array after sorting: @sortedArray\n\n"; @qwArray = qw (Hello Perl Array); print "Array after qw: \n"; print Dumper \@qwArray;	Type the following piece of code as shown. <<pause>> In this case, each word of the variable string will become an element of an Array. Here, each element of newArray will be joined by comma. sort function will sort the elements of newArray in alphabetical order. qw function creates an Array of words separated by space.
Slide	Let us understand each function.
Slide	split function takes two arguments. 1st is the delimiter by which the string needs to be split 2nd is the string which needs to be split. Delimiters can be specified in forward slash, single or double quotes.
Slide	join function takes 2 arguments. 1st is the delimiter by which the Array elements needs to be joined. 2nd is the Array. Delimiters can be specified in single or double quotes.
Slide	sort function takes a single argument, which is the Array that needs to be sorted.
Slide	qw function returns an Array of words, separated by space. It is not necessary to specify the word in quotes, if written using qw.
Press ctrl + s	Press Ctrl + S to save the file.
Switch to terminaland type perl arrayFunctions.pl	Then switch to the terminal and execute the Perl script by typing - perl arrayFunctions dot pl and press Enter.
Highlight the output on the terminal Declared String: Illustration Of Array Functions Array after split: $VAR1 = [ 'Illustration', 'Of', 'Array', 'Functions' ]; String After Join: Illustration, Of, Array, Functions Array after sorting: Array Functions Illustration Of Array after qw: $VAR1 = [ 'Hello', 'Perl', 'Array' ];	The following output is displayed on the terminal. <pause>
Slide: Summary	Let us summarize. In this tutorial, we have learnt to - add/remove elements from an Array basic functions which can be performed on Array using sample programs
Slide: Assignment	Here is assignment for you - 'script.spoken-tutorial.org/index.php/Perl script.spoken-tutorial.org/index.php/Perl]' split the above string at '/' delimiter Add https:// at the start of an newly created Array Remove element “Perl” from the Array Declare number Array and sort it
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Acknowledgment http://spoken-tutorial.org\NMEICT-Intro	Spoken Tutorial Project is a part of the Talk to a Teacher project It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this Mission is available spoken hypen tutorial dot org slash NMEICT hyphen Intro
	Hope you enjoyed this Perl tutorial. This is Amol Brahmankar signing off. Thanks for joining

Contributors and Content Editors

AmolBrahmankar, Nancyvarkey, PoojaMoolya