Difference between revisions of "PERL/C2/Arrays/English-timed"
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| − | |There are many ways by which we can find the length of an array | + | |There are many ways by which we can find the length of an array- |
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|02:46 | |02:46 | ||
| − | |Index of an array + 1 i.e. '''$#array + 1'''. | + | |* Index of an array + 1 i.e. '''$#array + 1'''. |
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|02:53 | |02:53 | ||
| − | |Using PERL inbuilt scalar function; i.e. '''scalar | + | |* Using PERL inbuilt scalar function; i.e. '''scalar open bracket @array close bracket.''' |
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|03:02 | |03:02 | ||
| − | |Assign array to a scalar variable i.e. '''$arrayLength = @array '''. | + | |* Assign array to a scalar variable i.e. '''$arrayLength = @array '''. |
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Revision as of 23:00, 4 November 2015
| Time | Narration |
| 00:01 | Welcome to the spoken tutorial on Arrays in Perl. |
| 00:06 | In this tutorial, we will learn about: |
| 00:09 | * Index of an array |
| 00:11 | * Length of an array |
| 00:13 | * Accessing elements of an array |
| 00:16 | * Looping over an array |
| 00:18 | * Sequential Array and |
| 00:20 | * Array Slicing. |
| 00:22 | Here, I am using Ubuntu Linux 12.04 operating system and Perl 5.14.2. |
| 00:30 | I will also be using the gedit Text Editor. |
| 00:34 | You can use any text editor of your choice. |
| 00:37 | You should have basic knowledge of variables, comments & data Structures in Perl. |
| 00:43 | Knowledge of loops and conditional statements will be an added advantage. |
| 00:48 | Please go through the relevant spoken tutorials on the Spoken Tutorial website. |
| 00:54 | Array is a simple data structure which contains elements of any data type. |
| 00:59 | Array index starts from zero always. |
| 01:03 | In Perl, it is not necessary to declare the length of an array. |
| 01:08 | Array length expands/shrinks as and when elements are added/removed from it. |
| 01:15 | The syntax for declaring an array is: |
| 01:18 | @myArray equal to open bracket 1 comma 2 comma 3 comma single quote abc single quote comma 10.3 close bracket semicolon. |
| 01:31 | The last index of an array can be found with this command: |
| 01:35 | $#myArray |
| 01:38 | Let us understand this using sample program. |
| 01:42 | Open the terminal and type: |
| 01:44 | gedit arrayIndex dot pl space ampersand |
| 01:50 | and press Enter. |
| 01:52 | This will open arrayIndex dot pl file in geditor. |
| 01:57 | Type the piece of code that is displayed on screen. |
| 02:02 | Here, we have declared & defined an array which contains 5 elements. |
| 02:07 | As array index starts from zero, the last index value will be 4 |
| 02:14 | i.e number of elements which is 5, minus 1. |
| 02:18 | Press Ctrl+S to save the file. |
| 02:22 | Now, switch to terminal and execute the Perl script. |
| 02:26 | Type: perl arrayIndex dot pl |
| 02:30 | and press Enter. |
| 02:32 | The output will be as displayed on the terminal. |
| 02:37 | Now, let us see how to get length of an array in Perl. |
| 02:41 | There are many ways by which we can find the length of an array- |
| 02:46 | * Index of an array + 1 i.e. $#array + 1. |
| 02:53 | * Using PERL inbuilt scalar function; i.e. scalar open bracket @array close bracket. |
| 03:02 | * Assign array to a scalar variable i.e. $arrayLength = @array . |
| 03:09 | Let us look at an illustration of an array length using a sample program. |
| 03:14 | Switch to the terminal and type: |
| 03:18 | gedit arrayLength dot pl space ampersand and |
| 03:24 | press Enter. |
| 03:27 | Type the following piece of code as shown on the screen. |
| 03:32 | Here, we have declared & defined an array which contains 5 elements. |
| 03:38 | So, output will display 5. |
| 03:41 | Highlighted are the various ways to find the length of an array in Perl. |
| 03:47 | Please note: We have concatenated the output in the print statement using comma. |
| 03:53 | Press Ctrl + S to save the file. |
| 03:57 | Now, let us execute the script. |
| 03:59 | Switch to terminal and type: |
| 04:02 | perl arrayLength dot pl and press Enter. |
| 04:07 | The output will be as displayed on the terminal. |
| 04:12 | Now, let us understand how to access individual elements in an array. |
| 04:18 | Indexing is used to access elements of an array. |
| 04:22 | Let us look at an example for accessing elements of an array at: |
| 04:27 | * First Position |
| 04:28 | * Last Position |
| 04:29 | * Any position. |
| 04:32 | Switch to the terminal and type: |
| 04:35 | gedit perlArray dot pl space ampersand |
| 04:42 | and press Enter. |
| 04:45 | Type the following piece of code as shown. |
| 04:49 | Please note: |
| 04:50 | myArray is declared with @ (at the rate) sign. |
| 04:54 | But, to access an array element we need to use $(dollar) sign. |
| 04:59 | To access the element at any position, we need to pass index to an array. |
| 05:07 | Here, to access the first element of myArray, |
| 05:11 | zero is passed as index. |
| 05:16 | To access the last element of myArray , we have passed the last index of myArray. |
| 05:24 | Recall, we had learnt about this earlier. |
| 05:28 | Press Ctrl + S to save the file. |
| 05:30 | Switch to the terminal and execute the script as: |
| 05:36 | perl perlArray dot pl |
| 05:41 | and press Enter. |
| 05:43 | The output will be as shown on the terminal. |
| 05:47 | Now, let us understand how to loop over each element of an array. |
| 05:52 | There are two ways of looping over an array: |
| 05:56 | * Using for loop |
| 05:58 | * Using foreach loop. |
| 06:01 | Let's learn how to use these loops to iterate over an array using a sample program. |
| 06:07 | For this, switch to the terminal and type: |
| 06:11 | gedit loopingOverArray dot pl space ampersand |
| 06:17 | and press Enter. |
| 06:20 | Type the piece of code as shown on the screen. |
| 06:24 | Here, we are printing each element of array by iterating the index. |
| 06:31 | The for loop will execute till the value of i variable reaches the last index of an array. |
| 06:38 | Here, foreach loop will be executed for each element of an array. |
| 06:46 | Once the array reaches its last element, it will exit the foreach loop. |
| 06:53 | Please Note: If you are not aware of for and foreach loops, |
| 06:58 | please go through the relevant spoken tutorials on "spoken tutorial" website. |
| 07:04 | Now, press Ctrl + S to save the file. |
| 07:07 | Then switch to the terminal and execute the script as: |
| 07:12 | perl loopingOverArray dot pl |
| 07:15 | and press Enter. |
| 07:19 | The output will be as displayed on the terminal. |
| 07:24 | In Perl, we can declare a sequential array as: |
| 07:28 | @alphaArray = open bracket a dot dot d close bracket semicolon |
| 07:37 | i.e alphaArray will contain elements 'a', 'b', 'c' and 'd'. |
| 07:44 | Similarly, @numericArray equal to open bracket 1 dot dot 5 close bracket semicolon is same as
@numericArray equal to open bracket 1 comma 2 comma 3 comma 4 comma 5. |
| 08:03 | Perl also provides array slicing. |
| 08:06 | This is nothing but extracting part of an array and dumping it into a new array. |
| 08:13 | @array = 19 comma 23 comma 56 comma 45 comma 87 comma 89 close bracket semicolon |
| 08:27 | @newArray = @array open square bracket 1 comma 4 close square bracket semicolon |
| 08:38 | After slicing, the newArray will look like: |
| 08:42 | @newArray = open bracket 23 comma 87 close bracket semicolon |
| 08:51 | Let us summarize. |
| 08:52 | In this tutorial, we have learnt to: |
| 08:55 | * Find index of an array |
| 08:57 | * Find length of an array |
| 08:59 | * Access elements of an array |
| 09:01 | * Loop over an array |
| 09:03 | * Sequential Array and |
| 09:05 | * Array Slicing, using sample programs. |
| 09:07 | Here is an assignment for you: |
| 09:10 | * Declare an array of rainbow colors. |
| 09:13 | * Print 4th element of this array. |
| 09:16 | * Print Length and last index of this array. |
| 09:19 | * Loop over each element of an array using for & foreach loops. |
| 09:25 | * Declare array as @myArray = open bracket 1..9 close bracket semicolon and then create an array of odd numbers from above array using array slicing. |
| 09:41 | Watch the video available at the following link. |
| 09:44 | It summaries the Spoken Tutorial project. |
| 09:48 | If you do not have good bandwidth, you can download and watch it. |
| 09:53 | The Spoken Tutorial project team: * Conducts workshops using spoken tutorials. |
| 09:58 | * Gives certificates to those who pass an online test. |
| 10:02 | For more details, please write to: contact at spoken hyphen tutorial dot org. |
| 10:09 | "Spoken Tutorial" project is a part of the "Talk to a Teacher" project. |
| 10:13 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 10:20 | More information on this mission is available at:
spoken hyphen tutorial dot org slash NMEICT hyphen Intro. |
| 10:31 | Hope you enjoyed this Perl tutorial. |
| 10:35 | This is Amol, signing off. |
| 10:37 | Thanks for joining. |
