PERL/C2/Data-Structures/English

Title Of Script: Data structures in Perl

Author: Amol Brahmankar

Keywords: Data structures in perl video tutorial.

Visual Clue	Narration
Slide	Welcome to the spoken tutorial on Data Structures in Perl
Slide: Learning Objectives	In this tutorial, we will learn about; Data Structures available in Perl
Slide: System Requirements	Here 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 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 has 3 types of data structure - 1. Scalar 2. Array 3. Hash. Also, called as Associative Array
Slide	Scalar: This type of data structure holds a value of any data type. The data type can be string, number, double etc. It can also hold the reference to an array or reference to a hash. Note: reference in Perl will be covered in subsequent tutorial.
Slide Declaring scalar data structure; $count = 12; $string = 'I am scalar of type string';	Scalar type of data structure is as simple as declaring the variable. $count = 12; $string = 'I am scalar of type string';
Slide	We can perform the following operations on scalar; Assign a value to it Assign one scalar to another Arithmetic operations on number type of scalars like add, subtract etc string operations on string scalar like concatenation, substr etc
	Now let us look at an example of scalar data structure.
Switch to terminal >> type gedit scalars dot pl & >> Enter.	Switch to terminal and type gedit scalars dot pl & and Press Enter.
Gedit #!/usr/bin/perl # Following are the various ways of declaring sclar $count = 12; $string = 'I am scalar of type string'; =head Few of the arithmatic operations that can be performed on the sclars =cut $newCount = $count; print "Original Count: $newCount\n"; $newCount = $newCount + 12; #Can be written as $newCount += 12; print "New Count After Addition: $newCount\n"; $newCount = $newCount - 12; #Can be written as $newCount -= 12; print "New Count After Substraction: $newCount\n"; =head Few of the string operations that can be performed on the sclars =cut $string = $string. ' in Perl'; #can be written as $string .= ' in Perl'; print "Original String: $string\n"; $newString = substr($string, 0, 11); print "New String: $newString\n";	This will open the scalars dot pl file in gedit. Type the code as displayed on the screen. This is the declaration and assignment to the scalar. These are few arithmetic operations that can be performed on number type of scalar <pause> These are string operations that can be performed on String type of scalar. <pause> substr is the PERL function which provides part of the string as output. Here index 0 specifies start of a string, i.e. from where we want to start extraction of the string. And 11 is the offset upto where we want the string to be in the output.
Press ctrl + s	Press ctrl + s to save the file.
Switch to terminal perl scalars.pl	Then switch to the terminal and execute the Perl script as perl scalars dot pl and press Enter.
Highlight the output on the terminal Original Count: 12 New Count After Addition: 24 New Count After Substraction: 12 String: I am scalar of type string in Perl New String: I am scalar	The output shown on terminal is as highlighted. <pause> << I Wiil just highlight the output and will not read it while recording >> Original Count: 12 New Count After Addition: 24 New Count After Substraction: 12 String: I am scalar of type string in Perl New String: I am scalar
Slide	Now, let us look at array data structure in perl.
	Array: It is a list of elements. Elements can be string, number etc. It has an index, which is used for performing various operations on the array. Index starts with zero. Unlike other programming languages, there is no need to declare an array or its length before using it in Perl. Perl array, stretches or shrinks as per the elements added or removed from it
Slide Highlight @variableName = (element 1, element 2, ..., element N);	The syntax to write an array is; at the rate variable name space equal to space open bracket list of elements separated with comma close bracket semicolon
	Now let us look at an example of array data structure.
Switch to terminal >> type gedit perlArray.pl & >> Enter.	Switch to terminal and type gedit perlArray dot pl & and Press Enter.
Gedit #!/usr/bin/perl #Number array @numArray = (98, 99, 92, 97); #String array @strArray = ('Perl', 'String', 'Array'); #Mix array @array = (98, 'StringValue', 92);	This will open the perlArray dot pl file in gedit. Type the following code as displayed on the screen This is the number array which has elements of number type This is the string array which has elements of string type This array has elements of both number and string type.
Gedit Highlight all 3 types of array print “Number Array: @numArray\n”; print “String Array: @strArray\n”; print “Array: @array\n”;	This example shows the various types of array in Perl. Now let us see how to print the array. Type print space double quote Number Array colon space at the rate numArray slash n double quote semicolon Press Enter Similarly print other 2 arrays as print “String Array: @strArray\n”; print “Array: @array\n”;
Press ctrl + s	Press ctrl + s to save the file
Switch to terminal perl perlArray.pl	Then switch to the terminal and execute the Perl script as perl perlArray dot pl and press Enter.
Highlight the output on the terminal Number Array: 98 99 92 97 String Array: Perl String Array Array: 98 StringValue 92	The following output is displayed on the terminal <pause> << I Wiil just highlight the output and will not read it while recording >> Number Array: 98 99 92 97 String Array: Perl String Array Array: 98 StringValue 92
Slide	Now, let us look at Hash data structure in Perl.
	Hash: Hash is alternatively called as Associative array. It is a Key Value pair data structure. Key in hash is unique. If the same key is added again, then the value of that key will be overridden by the latest value assigned to the key. Value can be duplicate. It also holds value of any data type.
Slide Highlight %variableName = ( 'Key1' => 'Value1' , 'Key2' => 'Value2' );	The syntax of hash is; percentage variable name space equal to space open bracket Press Enter single quote key Name single quote space equal to greater than sign space Value comma Press Enter single quote key Name single quote space equal to greater than sign space Value Press Enter close bracket semicolon
	Now let us look at an example of hash data structure.
Gedit	Switch to terminal and type gedit perlHash dot pl & and Press Enter.
Gedit #!/usr/bin/perl use Data::Dumper; #Hash of marks obtain in a subject %hash = ( 'Subject' => 'Math', 'Marks' => 98 );	This will open the perlHash dot pl file in gedit. Type the following code as displayed on the screen; This hash indicates the marks obtained in a subject.
Gedit Highlight print "Hash: ", Dumper \%hash;	This example, shows the use of hash. Now let us see how to print the hash. For now, just note the way I have printed the hash. Detailed explanation will be given in a subsequent tutorial.
Press ctrl + s	Press ctrl + s to save the file
Switch to terminal perl perlHash.pl	Then switch to the terminal and execute the Perl script as perl perlHash dot pl and press Enter.
Highlight the output on the terminal Hash: $VAR1 = { 'Subject' => 'Math', 'Marks' => 98 };	The following output is displayed on the terminal. <pause> << I Wiil just highlight the output and will not read it while recording >> Hash: $VAR1 = { 'Subject' => 'Math', 'Marks' => 98 };
Slide: Summary	Let us summarize. In this tutorial, we have learnt - scalar Array and Hash Data Structure in Perl using sample programs.
Slide: Assignment	Here is assignment for you - Declare scalar variable Assign value of type float to it and then print it. Declare and print an array of colors 'Red', 'Yellow' and 'Green'. Declare and print a hash of Employee Name and their department. Hint: 'Employee' => 'John', 'Department' => 'Engineering'
About the Project	Watch the video available at the following link It summaries the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it
Spoken Tutorial Workshops	The Spoken Tutorial Project Team Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to contact at spoken hyphen tutorial dot org
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 hyphen 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