PERL/C2/Arrays/English-timed

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 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	* Sequential 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.
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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.

Contributors and Content Editors

Gaurav, PoojaMoolya, Sandhya.np14