Difference between revisions of "PERL/C2/for-for-each-loops/English-timed"
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Revision as of 10:04, 8 May 2015
| Time | 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 Linux 12.04 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 and |
| 00:55 | * do-while loop. |
| 00:56 | In this tutorial, we will 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 | Type: print 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, and 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 us execute the Perl script by typing perl forLoop dot pl and press Enter. |
| 04:11 | The following output will be shown on the 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 ampersand and 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 equal to space open bracket ten comma twenty comma thirty close the bracket semicolon |
| 05:39 | press Enter. |
| 05:41 | foreach space dollar var space open bracket at the rate myarray close the 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' ($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 (\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 pl and press Enter. |
| 07:32 | The following line will be shown on the 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 the 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 summarizes 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 at 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. |
