PERL/C2/Functions-in-Perl/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Functions in PERL.
00:06	In this tutorial, we will learn about:
00:10	* PERL functions
00:11	* functions with arguments
00:13	* functions with return values.
00:16	For this tutorial, I am using:
00:18	* Ubuntu Linux 12.04 operating system
00:22	* Perl 5.14.2 and
00:24	* gedit Text Editor.
00:27	You can use any text editor of your choice.
00:31	You should have basic knowledge of variables, comments, loops, conditional statements and data Structures in PERL.
00:41	Please go through the relevant spoken tutorials on the Spoken Tutorial website.
00:47	We will first see some simple PERL functions.
00:51	In PERL, functions, also called as subroutines, are declared with sub keyword.
00:57	The definition of a declared function is written between curly braces.
01:03	This function does not take any arguments.
01:07	And, it does not return anything.
01:10	Note: function definition can be written anywhere in the script or in another module.
01:17	This module must then be included in the script, to use this function.
01:24	To include the module file in the script, one has to use the following syntax:
01:31	use ModuleFileName semicolon
01:35	Let us understand this using a sample program.
01:39	Open a file in your text editor and name it as simpleFunction dot pl.
01:46	Here is my simpleFunction dot pl file in gedit.
01:51	Type the code as displayed on the screen.
01:55	Here, we are just calling a function which we have defined.
02:00	Then the execution control is passed to that function.
02:06	This is the declaration & definition of the function.
02:10	This function will print out the given text.
02:14	Save your file.
02:17	Then switch to the terminal and execute the PERL script by typing:
02:24	perl simpleFunction dot pl
02:28	and press Enter.
02:30	The output will be as shown on the terminal.
02:38	Now, let us see a function with arguments.
02:44	Let us understand this function using a sample program.
02:48	Open a file in your text editor and name it as functionWithArgs dot pl.
02:57	Here is my functionWithArgs script in gedit.
03:02	Type the following piece of code as shown on the screen.
03:07	Here, we are calling the function with arguments 10 and 20.
03:13	The passed arguments are caught in '$var1' & '$var2'.
03:20	@_ is a special Perl variable. We will cover its details in future tutorials.
03:29	This function performs the addition of 2 variables and prints the answer.
03:37	Save your file.
03:42	@_is a special Perl array.
03:46	This array is used to store the passed arguments.
03:51	Similarly, we can catch the passed arguments in variables as:
03:56	$var1 space = space shift @_ semicolon
04:04	$var2 space = space shift @_ semicolon
04:12	shift @_ removes the element at first position from @_ array
04:21	and assigns it to a variable.
04:24	Another way is: $var1 space = space dollar underscore open square bracket zero close square bracket semicolon.
04:38	$var2 space = space dollar underscore open square bracket 1 close square bracket semicolon.
04:49	The above mentioned way is similar to the fetching elements of @_ array using index.
04:59	Now, switch to terminal and execute the script by typing:
05:06	perl functionWithArgs dot pl and press Enter .
05:14	The output is as displayed on the screen.
05:23	Now, let us look at a function which returns a single value.
05:32	Let us understand the same, using a sample program.
05:35	Let me switch to funcWithSingleRtrnVal dot pl script in gedit.
05:46	Open a file in your text editor and type the following piece of code as shown.
05:52	Here, we are calling addVariables function with parameters 10 and 20.
06:01	The return value of the function is caught in '$addition' variable.
06:09	This function does the addition of the passed parameters and returns the answer.
06:15	Save the file.
06:17	Now, let us execute the script.
06:20	So, switch to terminal and type:
06:24	perl funcWithSingleRtrnVal dot pl and press Enter.
06:35	The output is as displayed on the terminal.
06:43	Now, let us see a function which returns multiple values.
06:48	Let us understand the same, using a sample program.
06:53	In gedit, I have opened a file and named it as funcWithMultipleRtrnVals dot pl.
07:04	Please do like-wise in your text editor.
07:08	Now, type the following piece of code as shown.
07:13	Here, we are calling addVariables function with parameters 10 and 20.
07:21	The return values of the function are caught in variables $var1, $var2 and $addition.
07:31	This function does the addition and returns the passed parameters and the resultant answer.
07:42	This illustration demonstrates how we can return an array from a function.
07:53	Similarly, this demonstrates how hash can be returned from a function.
08:00	Save your file.
08:03	Now let us execute the Perl script on the terminal by typing:
08:10	perl funcWithMultipleRtrnVals dot pl
08:18	and press Enter.
08:20	The output is as displayed on the terminal.
08:32	Perl provides several inbuilt functions.
08:36	We learnt some of them in earlier tutorials. For e.g- arrays, Hash, sort, scalar, each, keys etc.
08:49	Calling inbuilt functions is similar to calling any other function which we define.
08:57	e.g sort open bracket @arrayName close bracket semicolon.
09:04	Try incorporating some inbuilt functions in the sample programs we used.
09:10	And observe their outputs.
09:13	Let us summarize.
09:15	In this tutorial, we have learnt:
09:17	* functions in Perl
09:19	* functions with arguments and
09:22	* functions which return values using sample programs.
09:27	Here is an assignment for you:
09:29	Write a function which takes 3 arguments.
09:33	Perform some action on these arguments.
09:37	Return the result of the action performed on the arguments and print the same.
09:43	Watch the video available at the following link.
09:47	It summarizes the Spoken Tutorial project.
09:51	If you do not have good bandwidth, you can download and watch it.
09:56	The Spoken Tutorial project team: * Conducts workshops using spoken tutorials.
10:02	* Gives certificates to those who pass an online test.
10:07	For more details, please write to: contact at spoken hyphen tutorial dot org.
10:14	"Spoken Tutorial" project is a part of the "Talk to a Teacher" project.
10:19	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:28	More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
10:40	Hope you enjoyed this Perl tutorial.
10:43	This is Amol, signing off.
10:46	Thanks for joining.

Contributors and Content Editors

Gaurav, PoojaMoolya, Sandhya.np14