Ruby/C2/Control-Statements/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Control Statements in Ruby.
00:06	In this tutorial, we will learn to use:
00:08	'if' statement , 'elsif' statement
00:11	'else, 'case' statements.
00:14	Here we are using: Ubuntu version 12.04
00:18	Ruby 1.9.3.
00:21	To follow this tutorial, you must have Internet connection.
00:24	You must also have knowledge of Linux commands, Terminal and Text-editor.
00:30	If not, for relevant tutorials, please visit our website.
00:34	Before we begin, recall that we had created “ttt” directory earlier.
00:38	Let's go to that directory.
00:41	Then to ruby hyphen tutorial control hyphen statements.
00:47	Now that we are in that folder, let’s move ahead.
00:52	The syntax of the 'if' statement in Ruby is as follows:
00:56	if “condition”
00:58	ruby code. end
01:01	Let us look at an example.
01:03	Create a new file in gedit as shown in the basic level Ruby tutorials.
01:08	Name it if hyphen statement dot rb.
01:12	I have a working example of the if statement.
01:15	You can pause the tutorial and type the code as we go through it.
01:19	I have declared an if statement in this example.
01:23	First, I declare a local variable my_num and assign the value 2345 to it.
01:31	Then I declare an if statement.
01:34	The puts method declared within the if statement will display the output.
01:39	The if statement will check if the value of my_num is greater than 0.
01:43	If it is, it will print out the specified string.
01:47	Now, let us switch to the terminal and type:
01:51	ruby space if hyphen statement dot rb.
01:57	The output will display “The value of my_num is greater than 0”.
02:02	This output proves that the if condition returned true.
02:07	You should now be able to write your own 'if' statement in Ruby.
02:12	Let's look at the 'if-else' statement next.
02:16	The syntax for using else is:
02:18	if “condition” , ruby code
02:20	else, ruby code
02:22	end
02:24	Let us look at an example.
02:26	Create a new file in gedit as shown in the basic level Ruby tutorials.
02:30	Name it if hyphen else hyphen statement dot rb.
02:37	I have a working example of the 'if-else' statement.
02:40	You can pause the tutorial and type the code as we go through it.
02:44	I have declared an if-else statement in this example.
02:48	First I declare a local variable my_num and assign the value of -1 to it.
02:55	Then I declare an if statement.
02:58	The 'if' statement will check if the value of 'my_num' is greater than 0.
03:03	If it is, it will print out the specified string.
03:06	If not, it will go to the else statement.
03:10	And it will print out the string that is specified there.
03:13	Now, let us switch to the terminal and type:
03:18	ruby space if hyphen else hyphen statement dot rb
03:26	and see the output.The output will display “The value of my_num is lesser than 0”.
03:32	This shows that the else statement was executed.
03:35	You should now be able to write your own if-else statement in Ruby.
03:41	Let's look at the if-elsif statement next.
03:45	The syntax for using elsif is:
03:48	if “condition” ruby code
03:50	elsif “condition” ruby code
03:52	else ruby code
03:54	end . Let us look at an example.
03:58	Create a new file in gedit as shown in the basic level Ruby tutorials.
04:01	Name it if hyphen elsif hyphen statement dot rb.
04:07	I have a working example of the if-elsif statement.
04:10	You can pause the tutorial and type the code as we go through it.
04:14	I have declared an if-elsif statement in this example.
04:19	Here also, I have declared a local variable my_num and assigned the value -1 to it.
04:25	Then I declare an if statement.
04:28	The if statement will check if the value of my_num is greater than 0.
04:32	If it is, it will print out the specified string.
04:35	If this is not true, it will go into the elsif section.
04:39	It will now check if the value of my_num is equal to -1.
04:43	If it is true, it will print out the string that is specified there.
04:46	If the value of my_num is neither greater than 0 nor equal to -1, it will go into the else section.
04:54	But, since the value of my_num = -1 it will not proceed to the else block.
05:00	And, it will exit the conditional statement.
05:03	Now, let us switch to the terminal and type:
05:07	ruby space if hyphen elsif hyphen statement dot rb
05:15	and see the output.
05:17	The output will display “The value of my_num is -1 and is lesser than 0”.
05:23	Let's go back to our file and change the value of my_num to 5.
05:29	Let's save the code and execute it on the terminal.
05:35	So, now it fulfills the if condition and the specified string is printed.
05:42	"The value of my_num is greater than 0".
05:45	Let's go back to our file and change the value of my_num to -5.
05:50	Let's save the code and execute it on the terminal.
05:55	In this case, it fulfills the else condition and the puts statement within the else block gets executed.
06:03	You should now be able to write your own if-elsif statement in Ruby.
06:08	Let us look at the 'case' statement next.
06:12	The 'case' statement is a control flow statement based on a particular selection.
06:17	Let us look at the syntax of the 'case' statement in order to understand this statement.
06:22	The syntax for using case is:
06:24	case variable
06:26	when “value 1”
06:28	ruby code . when “value 2” ruby code
06:31	else ruby code . end.
06:35	Let us look at an example.
06:37	Create a new file in gedit as shown in the basic level Ruby tutorials.
06:41	Name it case hyphen statement dot rb.
06:44	I have a working example of the 'case' statement.
06:48	You can pause the tutorial and type the code as we go through it.
06:52	I have declared a case statement in this example.
06:55	Here, I have a print statement which will print a question on the terminal.
07:01	Then I call a gets which will accept a single line of data from the standard input.
07:09	Then I strip the input data of any new line characters using chomp.
07:15	I assign the result to a variable named domain.
07:18	Then I declare a case statement.
07:22	Within that, I declare a when statement .
07:25	This checks whether the specified string matches the value of domain.
07:30	First, it checks whether the value of domain is “UP”.
07:34	If it is so, it will print out “Uttar Pradesh” and exit the case statement.
07:39	If domain is not “UP”, it checks whether the value of domain is “MP”.
07:44	If it is so, it will print out “Madhya Pradesh” and so on.
07:48	It will continue checking the value of domain if no match was found so far.
07:53	At this point, it will encounter the else statement
07:56	as none of the above conditions were true.
07:59	It will subsequently execute the ruby code that follows the else declaration.
08:03	It will print “Unknown” as per our example.
08:07	Now, save the file. Switch to the terminal and type:
08:11	ruby space case hyphen statement dot rb.
08:18	“Enter the state you live in:” will be displayed on the terminal.
08:22	Type in “UP” and see the output.
08:25	The output will display “Uttar Pradesh”.
08:28	Next, execute the Ruby file again, like before.
08:31	This time, at the prompt, type: “KL” and see the output.
08:36	It will print “Kerala”.
08:38	Next, execute the file one more time.
08:41	This time, at the prompt, type in “TN” and see the output.
08:47	It will print “Unknown”.
08:50	This is because none of the cases were satisfied. So, the default else statement is executed.
08:58	You should now be able to write your own case-statements in Ruby.
09:03	This brings us to the end of this Spoken Tutorial.
09:07	Let's summarize. In this tutorial, we have learnt to use:
09:10	if statement
09:12	else construct, if-elsif and
09:15	case statements.
09:17	As an assignment- write a Ruby program
09:20	that prompts a user to enter a number,
09:23	then use the appropriate control-statement
09:26	to check if the number is a multiple of 2.
09:29	If it is, then print: “The number entered is a multiple of 2”.
09:35	If not, it should check- if it is a multiple of 3.
09:38	If it is, then print: “The number entered is a multiple of 3”.
09:43	If not, it should check if it is a multiple of 4.
09:47	If it is, then print: “The number entered is a multiple of 4”.
09:51	If not, it should print: “The number is not a multiple of 2, 3 or 4”.
09:56	Watch the video available at the following link.
10:00	It summarizes the Spoken Tutorial project.
10:03	If you do not have good bandwidth, you can download and watch it.
10:07	The Spoken Tutorial project team:
10:09	Conducts workshops using spoken tutorials.
10:13	Gives certificates to those who pass an online test.
10:16	For more details, please write to: contact@spoken-tutorial.org
10:21	Spoken Tutorial project is a part of the Talk to a Teacher project.
10:26	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:32	More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
10:41	This is Anjani Nair, signing off. Thanks for watching.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14