PERL/C2/for-for-each-loops/English

Title Of Script: for & foreach Loops in Perl

Author: Amol Brahmankar

Keywords: Loops in Perl, for loop in perl, foreach in perl, video tutorial.

Visual Clue	Narration
Slide	Welcome to the spoken tutorial on for and foreach Loops in Perl
Slide: Learning Objectives	In this tutorial, we will learn about: for loop in Perl and foreach loop in Perl
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 and Comments in Perl. If not, please go through the relevant spoken tutorials on the spoken tutorial website.
Slide	Perl provides a mechanism by which we can check a condition repeatedly for various values. This is done using loops.
Slide	There are various types of loops in Perl; for loop foreach loop while loop & do-while loop In this tutorial, we'll cover for and foreach loop.
Slide	for loop in Perl can be used to execute a piece of code for a certain number of times.
Slide for (variable initialization; condition; increment/decrement) { Piece of code to be executed multiple times }	The syntax of for loop is as follows: for space open bracket variable initialization semicolon condition semicolon increment close bracket Press Enter Open curly brackets Piece of code to be executed multiple times Close curly brackets		Now let us look at an example of a for loop.
Switch to the Terminal and type gedit forLoop.pl & and press Enter.	Open the Terminal and type; gedit forLoop.pl space & (ampersand) and press Enter
Point to the filename forLoop.pl in the Titlebar of gedit.	This will open the forLoop.pl file in gedit.
Type the piece of code and save the file #!/usr/bin/perl for ($i=0; $i<=4; $i++) { print “Value of i: $i\n”; }	Type the following piece of code; hash exclamation mark slash u s r slash bin slash perl Press Enter for space open bracket dollar i equals to zero semicolon space dollar i less than or equal to four semicolon space dollar i plus plus close bracket space Open curly bracket press enter , type print space double quote Value of i colon space dollar I slash n double quote complete semicolon And Press Enter now ANd Close curly bracket
Press ctrl+s	Press Ctrl+S to save the file.
Highlight $i=0	Let me explain what the for loop does. The variable i is initialized to zero.
Highlight $i<=4	Next, the condition is checked. In this case, the condition is i is less than or equal to 4. If this condition is true, the code within the curly bracket will be executed.
Highlight print	This means the first print statement “Value of i: 0” will be displayed on the terminal.
Highlight $i++	After this, the variable i is incremented by 1.
Highlight $i<=4	And the for loop condition is checked once again. This loop will exit when the value of i becomes greater than 4.
	In this case, the for loop will be executed for i = 0, 1, 2, 3, 4 which is a total of 5 times.
Switch to terminal	Now, switch to the terminal.
perl -c forLoop.pl	Type the following to check for any compilation or syntax error: perl hyphen c forLoop dot pl and press Enter.
Highlight the below line on terminal; forLoop.pl syntax OK	Here it displays a message forLoop.pl syntax OK So, we have no errors.
Execute perl script perl forLoop.pl	Now, let's execute the Perl script by typing perl forLoop dot pl and press Enter.
Highlight/point to the output of the perl script on terminal Value of i: 0 Value of i: 1 Value of i: 2 Value of i: 3 Value of i: 4	The following output will be shown on terminal.
	Now, let us look at the foreach loop.
Slide	If we want to iterate a condition for an array, we can make use of foreach loop.
Slide foreach $variable (@array) { perform action on each element of an array }	The syntax is: foreach space dollar variable space within brackets at the rate array space open curly bracket perform action on each element of an array Press Enter Close the curly bracket. Please note: We'll cover array, array initialization and defining an array in subsequent tutorials.
	Now let us look at an example of foreach loop.
Switch to the Terminal and type gedit foreachLoop.pl & and press Enter.	Open the Terminal and type gedit foreachLoop dot pl space ampersand and Press Enter
Point to the filename foreachLoop.pl in the Titlebar of gedit.	This will open the foreachLoop.pl file in gedit.
#!/usr/bin/perl @myarray = (10, 20, 30); foreach $var (@myarray) { print “Element of array is: $var \n”; }	Type the following piece of code hash exclamation mark slash u s r slash bin slash perl and Press Enter at the rate myarray is equal to open bracket ten comma space twenty comma space thirty close bracket semicolon press enter foreach space dollar var space open bracket at the rate myarray close bracket space Open curly bracket press enter and type print space double quote Element of array is colon dollar var space slash n double quote complete semicolon Press Enter and Close curly bracket
Press Ctrl+S	Press ctrl+s to save the file.
Highlight @myarray = (10, 20, 30);	Let me explain what this code does. An array myarray is declared. It has 3 elements 10, 20 and 30.
Highlight $var	In each iteration of foreach loop dollar var will contain the single element of an array
Highlight foreach $var (@myarray)	foreach keyword will repeat this loop for each element of an array.
Highlight print “Element of array is:$var \n”;	That is, the code within the curly bracket will be executed for each myarray element.
Highlight \n	Back-slash n will place the prompt on a new line.
	This means the first element '10' will be displayed on the terminal. Then 20 and so on, till all the elements are printed.
Highlight foreach	This loop will exit after printing all the elements in myarray.
Switch to terminal perl -c foreachLoop.pl	Now, switch to terminal and type the following to check for any compilation or syntax error. type perl hyphen c foreachLoop dot pl and press Enter.
Highlight the below line on terminal; foreachLoop.pl syntax OK	The following line will be shown on terminal
Execute perl script perl foreachLoop.pl	There are no compilation or syntax errors. So let us execute the Perl script. Type perl foreachLoop dot pl and press Enter
Highlight the output of the perl script on terminal Element of an array is: 10 Element of an array is: 20 Element of an array is: 30	The following output will be shown on terminal.
	So, that's it about for loop and foreach loop.
Slide : Summary	Let us summarize. In this tutorial, we have learnt - for loop and foreach loop in Perl using some sample programs.
Assignment	Here is an assignment for you - Declare a string as 'Spoken Tutorial' and Print it 5 times Declare an array of colours as @colorArray = ('red', 'white', 'blue') and Print the element of an array using foreach loop
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 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, PoojaMoolya, Sneha