Difference between revisions of "PERL/C2/Array-functions/English-timed"
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Revision as of 01:41, 7 November 2015
| Time | Narration |
| 00:01 | Welcome to the spoken tutorial on Array Functions in PERL. |
| 00:06 | In this tutorial, we will learn about array functions in PERL like: |
| 00:11 | * push |
| 00:11 | * pop |
| 00:12 | * shift |
| 00:14 | * unshift |
| 00:15 | * split |
| 00:16 | * splice and |
| 00:17 | * join |
| 00:18 | * sort |
| 00:19 | * qw. |
| 00:20 | I am using Ubuntu Linux 12.04 operating system and Perl 5.14.2. |
| 00:28 | I will also be using the gedit Text Editor. |
| 00:32 | You can use any text editor of your choice. |
| 00:36 | You should have basic knowledge of variables, data Structures and arrays in PERL. |
| 00:43 | Knowledge of comments, 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 | Perl provides certain inbuilt functions. |
| 00:57 | These functions can perform various operations on an array. |
| 01:02 | Let us first learn how to add and remove elements from the last position of an array. |
| 01:08 | This can be done by using |
| 01:10 | push function which adds an element at the last position of an array |
| 01:15 | and pop function which removes an element from the last position of an array. |
| 01:21 | Let us understand push and pop functions by using a sample program. |
| 01:26 | Open the terminal and type: gedit perlArray dot pl space ampersand |
| 01:33 | and press Enter. |
| 01:36 | This will open 'perlArray dot pl' file in gedit. |
| 01:41 | Type the code as shown on the screen. |
| 01:45 | Here, we have declared an array of length 3. |
| 01:50 | push function will insert an element at the last position of this array i.e after 3 |
| 01:57 | whereas pop function will remove an element from the last position of the array. |
| 02:04 | In our case, 4 will be removed from the array. |
| 02:08 | Press Ctrl + S to save the file. |
| 02:11 | push function takes 2 arguments- |
| 02:14 | 1st argument to the push function is the array in which to add an element. |
| 02:20 | 2nd argument is the element which is to be pushed into the array. |
| 02:25 | The syntax of pop function is as follows: |
| 02:29 | pop function takes only one argument. |
| 02:32 | It is the array from which an element needs to be removed. |
| 02:36 | Note: Both these functions work at the last position of an array. |
| 02:41 | The element removed by pop function can be collected into another variable. |
| 02:46 | The syntax for this is $variable space = space pop open bracket @myArray close bracket . |
| 02:57 | Now switch to the terminal and execute the Perl script. |
| 03:01 | Type: perl perlArray dot pl and press Enter. |
| 03:07 | The output is as shown on the terminal. |
| 03:11 | Now, let us see how to add/remove an element from the 1st position of an array. |
| 03:18 | This can be achieved using- |
| 03:20 | * unshift function which adds an element to an array at the 1st position. |
| 03:25 | * shift function which removes the first element from an array. |
| 03:31 | Let us understand this using a sample program. |
| 03:35 | I will open perlArray dot pl file which I have already created. |
| 03:39 | Type the following piece of code as shown on the screen. |
| 03:43 | unshift function will insert an element at the first position i.e before 1. |
| 03:52 | shift function will remove an element from the first position. |
| 03:57 | In our case, zero will be removed. |
| 04:00 | Press Ctrl + S to save the file. |
| 04:03 | The unshift function takes 2 arguments- |
| 04:06 | 1st argument is the array in which to add an element, |
| 04:10 | 2nd argument is the element to be added into the array . |
| 04:15 | shift function takes only one argument - |
| 04:18 | This is the array from which the element needs to be removed. |
| 04:22 | Note: Both these functions work at first position of an array. |
| 04:27 | We can collect the element removed by shift function into some variable. |
| 04:33 | The syntax for this is: $variable space = space shift open bracket @myArray close bracket. |
| 04:44 | Then switch to the terminal and execute the Perl script. |
| 04:48 | Type: perl perlArray dot pl and press Enter. |
| 04:54 | The output displayed on the terminal is as highlighted. |
| 04:59 | Now, let us see how to remove an element from a specified position of an array. |
| 05:05 | splice function removes an element from a specified position of an array. |
| 05:11 | The return value of this function is an array of removed elements. |
| 05:17 | Let us understand this using a sample program. |
| 05:21 | Go to the perlArray dot pl file which we created earlier. |
| 05:26 | Type the piece of code as shown on the screen. |
| 05:30 | We need to provide index from where we want to remove the elements and |
| 05:35 | the offset up to which we want to remove the elements. |
| 05:39 | In our case, the elements 5 and 6 will be removed. |
| 05:44 | Then switch to the terminal and execute the Perl script by typing: |
| 05:49 | perl perlArray dot pl and press Enter. |
| 05:55 | The output is as shown on the terminal. |
| 05:59 | Now, let us look at few other inbuilt functions of arrays. |
| 06:04 | split function is used to divide a string at a specified delimiter. |
| 06:10 | The return value of this function is an array. |
| 06:14 | The elements of this array are the divided portions of the string. |
| 06:19 | join function joins the elements of an array using the specified delimiter. |
| 06:25 | It returns a string of joined elements. |
| 06:28 | sort function sorts an array in alphabetical/numerical order. |
| 06:34 | qw function returns an array of words, separated by a white space. |
| 06:40 | Now, let us understand all these functions using a sample program. |
| 06:45 | Switch to terminal and type: |
| 06:48 | gedit arrayFunctions dot pl space ampersand and press Enter. |
| 06:55 | Type the following piece of code as shown on screen. |
| 07:00 | In this case, each word of the variable string will become an element of an array. |
| 07:07 | Here, each element of newArray will be joined by comma. |
| 07:12 | sort function will sort the elements of an array in alphabetical order. |
| 07:19 | qw function creates an array of words separated by space. |
| 07:25 | Let us understand each function. |
| 07:28 | split function takes two arguments. |
| 07:31 | 1st argument is the delimiter by which the string needs to be split, |
| 07:36 | 2nd is the string which needs to be split. |
| 07:39 | Delimiters can be specified in forward slash, single or double quotes. |
| 07:45 | join function takes 2 arguments. |
| 07:48 | 1st is the delimiter by which the array elements need to be joined. |
| 07:53 | 2nd is the array. |
| 07:55 | Delimiters can be specified in single or double quotes. |
| 07:58 | sort function takes a single argument which is the array that needs to be sorted. |
| 08:05 | qw function returns an array of words, separated by space. |
| 08:11 | It is not necessary to specify the word in quotes if written using qw. |
| 08:17 | Then switch to the terminal and execute the Perl script by typing: |
| 08:23 | perl arrayFunctions dot pl |
| 08:26 | and press Enter. |
| 08:29 | The following output is displayed on the screen. |
| 08:33 | Let us summarize. |
| 08:34 | In this tutorial, we have learnt to: |
| 08:36 | * add/remove elements from an array |
| 08:40 | * basic functions which can be performed on array using sample program. |
| 08:46 | Here is an assignment for you - |
| 08:48 | 'script.spoken-tutorial.org/index.php/Perl' |
| 08:54 | Split the above string at '/ ' (forward slash) delimiter. |
| 08:59 | Add https:// at the start of a newly created array. |
| 09:06 | Remove element “Perl” from the array. |
| 09:09 | Declare a number array and sort it. |
| 09:12 | Watch the video available at the following link. |
| 09:15 | It summarizes the "Spoken Tutorial" project. |
| 09:19 | If you do not have good bandwidth, you can download and watch it. |
| 09:24 | The "Spoken Tutorial" project team: Conducts workshops using spoken tutorials. |
| 09:30 | Gives certificates to those who pass an online test. |
| 09:34 | For more details, please write to: contact at spoken hyphen tutorial dot org. |
| 09:40 | "Spoken Tutorial" project is a part of the "Talk to a Teacher" project. |
| 09:44 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 09:51 | More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro. |
| 10:02 | Hope you enjoyed this Perl tutorial. |
| 10:04 | This is Amol, signing off. |
| 10:06 | Thanks for joining. |
