Difference between revisions of "PERL/C2/Arrays/English-timed"
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Revision as of 11:28, 13 June 2014
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| 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 |
| 00.20 | And Array Slicing |
| 00.22 | Here I am using Ubuntu Linux12.04 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 array length using a sample program. |
| 03.14 | Switch to the terminal and type - |
| 03.18 | gedit arrayLength dot pl space ampersand |
| 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 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 | Sequenial Array |
| 09.05 | Array Slicing using sample programs. |
| 09.07 | Here is 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. |
