Difference between revisions of "PERL/C2/for-for-each-loops/English-timed"

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Revision as of 11:33, 28 May 2014

Visual Cue
Narration
00.01 Welcome to the spoken tutorial on for and foreach Loops in Perl
00.06 In this tutorial, we will learn about: for loop in Perl and
00.11 foreach loop in Perl
00.13 I am using Ubuntu Linux12.04 operating system and Perl 5.14.2


00.21 I will also be using the gedit Text Editor.


00.25 You can use any text editor of your choice.
00.29 You should have basic knowledge of Variables and Comments in Perl.


00.33 If not, please go through the relevant spoken tutorials on the spoken tutorial website.
00.40 Perl provides a mechanism by which we can check a condition repeatedly for various values. This is done using loops.
00.49 There are various types of loops in Perl;
00.52 for loop
00.53 foreach loop
00.54 while loop &
00.55 do-while loop


00.56 In this tutorial, we'll cover for and foreach loop.
01.01 for loop in Perl can be used to execute a piece of code for a certain number of times.
01.07 The syntax of for loop is as follows:
01.10 for space open bracket variable initialization semicolon condition semicolon increment
01.20 close bracket Press Enter


01.22 Open curly brackets


01.24 Piece of code to be executed multiple times


01.28 Close curly brackets
01.30 Now let us look at an example of a for loop.
01.33 Open the Terminal and type; gedit forLoop.pl space & (ampersand)
01.42 and press Enter
01.43 This will open the forLoop.pl file in gedit.
1.48 Type the following piece of code;hash exclamation mark slash u s r slash bin slash perl


01.58 Press Enter
02.00 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
02.18 space
02.19 Open curly bracket press enter
02.21 typeprint space double quote Value of i colon space dollar i slash n double quote complete semicolon


02.35 And Press Enter
02.36 now close curly bracket
02.39 Press Ctrl+S to save the file.
02.42 Let me explain what the for loop does.
02.46 The variable i is initialized to zero.
02.50 Next, the condition is checked.
02.53 In this case, the condition is i less than or equal to 4.


02.59 If this condition is true, the code within the curly bracket will be executed.
03.05 This means the first print statement "Value of i colon 0"
03.11 will be displayed on the terminal.
03.14 After this, the variable i is incremented by 1.
03.18 And the for loop condition is checked once again.


03.23 This loop will exit when the value of i becomes greater than 4.
03.29 In this case, the for loop will be executed for i = 0, 1, 2, 3, 4


03.38 which is a total of 5 times.
03.41 Now, switch to terminal.
03.44 Type the following to check for any compilation or syntax error:
03.48 perl hyphen c forLoop dot pl


03.54 and press Enter.
03.56 Here it displays a message
03.58 forLoop.pl syntax OK


04.01 So, we have no errors.
04.03 Now, let's execute the Perl script by typing perl forLoop dot pl and press Enter.
04.11 The following output will be shown on terminal.
04.16 Now, let us look at foreach loop.
04.19 If we want to iterate a condition for an array, we can make use of foreach loop.
04.25 The syntax is: foreach space dollar variable space within brackets at the rate array space


04.35 open curly bracket


04.37 perform action on each element of an array Press Enter
04.42 Close the curly bracket.
04.44 Please note: We'll cover array, array initialization and defining an array in subsequent tutorials.
04.52 Now let us look at an example of foreach loop.
04.56 Open the Terminal and type gedit foreachLoop dot pl space ampersandand Press Enter
05.08 This will open the foreachLoop.pl file in gedit.
05.12 Type the following piece of code
05.15 hash exclamation mark slash u s r slash bin slash perl and Press Enter
05.25 at the rate myarray space is equal to space open bracket ten comma twenty comma thirty close bracket semicolon
05.39 press enter
05.41 foreach space dollar var space open bracket at the rate myarray close bracket space
05.52 Open curly bracket press enter and type


05.56 print space double quote Element of an array is colon dollar var slash n double quote complete semicolon


06.13 Press Enter and Close the curly bracket
06.17 Press ctrl+s to save the file.
06.20 Let me explain what this code does. An array myarray is declared.
06.27 It has 3 elements 10, 20 and 30.
06 .33 In each iteration of foreach loop dollar var will contain the single element of an array
06.40 foreach keyword will repeat this loop for each element of an array.
06.47 That is, the code within the curly bracket will be executed for each myarray element.
06.55 Back-slash n will place the prompt on a new line.
07.00 This means the first element '10' will be displayed on the terminal.
07.06 Then 20 and so on, till all the elements are printed.
07.12 This loop will exit after printing all the elements in myarray.
07.17 Now, switch to terminal and type the following to check for any compilation or syntax error.
07.24 type perl hyphen c foreachLoop dot pland press Enter.
07.32 The following line will be shown on terminal
07.36 There are no compilation or syntax errors.
07.38 So let us execute the Perl script.


07.41 Type perl foreachLoop dot pl and press Enter
07.48 The following output will be shown on terminal.
07.54 So, that's it about for loop and foreach loop.
07.57 Let us summarize.
07.59 In this tutorial, we have learnt -
08.02 for loop and foreach loop in Perl
08.06 using some sample programs.
08.07 Here is an assignment for you -
08.10 Declare a string as 'Spoken Tutorial' and
08.13 Print it 5 times
08.16 Declare an array of colors as @colorArray = open bracket in single quote red comma white comma blue close the bracket and
08.32 Print the element of an array using foreach loop
08.36 Watch the video available at the following link


08.40 It summaries the Spoken Tutorial project


08.43 If you do not have good bandwidth, you can download and watch it
08.48 The Spoken Tutorial Project Team Conducts workshops using spoken tutorials


08.55 Gives certificates to those who pass an online test


08.59 For more details, please write to contact at spoken hyphen tutorial dot org
09.07 Spoken Tutorial Project is a part of the Talk to a Teacher project


09.12 It is supported by the National Mission on Education through ICT, MHRD, Government of India.


09.20 More information on this Mission is available spoken hyphen tutorial dot org slash NMEICT hyphen Intro
09.31 Hope you enjoyed this Perl tutorial.
09.34 This is Amol signing off.


09.36 Thanks for joining.

Contributors and Content Editors

Gaurav, Madhurig, PoojaMoolya, Sandhya.np14, Sneha

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