Ruby/C3/while-and-until-Looping-Statements/English-timed

Time	Narration
00:01	Welcome to the tutorial on while and until loops in Ruby.
00:06	In this tutorial, we will learn to use-
00:09	'while' loop , 'until' loop
00:11	redo and break.
00:13	We are using: Ubuntu version 12.04
00:17	Ruby 1.9.3
00:20	To follow this tutorial, you must have Internet connection.
00:25	You must also have knowledge of Linux commands, Terminal and Text-editor.
00:29	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 and looping hyphen statements directories.
00:46	Now that we are in that folder, let’s move ahead.
00:50	The syntax of the while loop in Ruby is as follows:
00:54	while “boolean expression”
00:56	ruby code , end
00:58	Let us look at an example.
01:01	Create a new file in gedit as shown in the basic level Ruby tutorials.
01:05	Name it while hyphen loop dot rb.
01:09	I have a working example of the 'while' loop.
01:13	Now, let us switch to the terminal and type: gedit space while hyphen loop dot rb space & (ampersand)
01:24	You can pause the tutorial, type the code as we go through it.
01:28	I have declared a while loop in this example.
01:32	First, I declared a local variable 'i' and initialized it with value 0.
01:38	Then I declare a 'while' loop.
01:41	This loop will execute as long as the variable 'i' is greater than -10.
01:46	The puts method, declared within the while loop, will display the output.
01:51	After the output is displayed, we decrement the value of 'i' by 1.
01:56	'i' will adopt this decremented value before the next iteration.
02:01	The variable 'i' gets decremented in every iteration.
02:04	This goes on till 'i' reaches the value -10.
02:09	At this point, the 'while' condition fails.
02:12	It subsequently breaks out of the loop and stops printing the output.
02:16	Now, let us switch to the terminal and type: ruby space while hyphen loop dot rb and see the output.
02:30	The output will consist of a list of numbers 0 through -9.
02:35	You should now be able to write your own while loop in Ruby.
02:40	Let's look at the until loop next.
02:43	The syntax for the until loop in Ruby is -
02:45	until “boolean expression”
02:47	ruby code , end
02:50	Let us look at an example.
02:52	Now,let us switch to the terminal and type: gedit space until hyphen loop dot rb space & (ampersand)
03:03	You can pause the tutorial and type the code as we go through it.
03:07	I have declared an until loop in this example.
03:12	We had declared a local variable 'i' and initialized it to 0.
03:16	Then we declare an until loop.
03:18	This loop will execute as long as the variable 'i' is greater than -10.
03:23	The 'puts' method will display the output.
03:27	After the output is displayed, value of 'i' is decremented by 1.
03:32	'i' will adopt this decremented value before the next iteration.
03:36	The variable 'i' gets decremented during every iteration.
03:40	This goes on till 'i' reaches the value -11.
03:43	At this point, the 'until' condition fails.
03:46	Subsequently, it breaks out of the loop and stops printing the output.
03:51	Now, switch to the terminal and type: ruby space until hyphen loop dot rb and see the output.
04:03	The output will consist of a list of numbers 0 through -10.
04:08	You should now be able to write your own until loop in Ruby.
04:13	Let's now move on to the redo construct.
04:16	The syntax for redo in Ruby is as follows:
04:20	a collection of objects. each do item
04:25	a conditional statement
04:27	ruby code , redo
04:29	end conditional, end loop
04:32	I have a working example of the redo loop.
04:35	Now, let us switch to the terminal and type: gedit space redo hyphen loop dot rb space &(ampersand )
04:48	You can pause the tutorial and type the code as we go through it.
04:52	I have declared an each loop in this example.
04:55	We have declared an each loop to iterate through numbers 10 to 20.
05:00	Then, we define an if conditional statement.
05:04	The loop will execute for every number between 10 to 20.
05:08	It will enter the inner conditional if conditional block only if the value of 'i' is equal to 20.
05:15	The 'puts' method, declared within the each loop, displays the output.
05:20	Once the program enters the 'if' conditional block, it will first print the output.
05:24	Then it will execute redo.
05:28	redo will execute the iteration of the most internal loop.
05:31	It will do so, without checking the loop condition.
05:34	Our condition being if i == 20,
05:38	the result will be an infinite loop, since the value of 'i' will not change from 20.
05:43	Let's switch to the terminal and type: ruby space redo hyphen loop dot rb
05:52	and see the output. The output will consist of an infinite loop that never ends.
05:58	Press Ctrl + C to terminate the infinite loop.
06:03	Now, let us look at the break statement.
06:06	The syntax for the break statement in Ruby is -
06:10	a looping statement
06:12	a conditional statement , break
06:14	end conditional
06:16	ruby code, end loop
06:18	Let us look at an example.
06:21	Now, let us switch to the terminal and type: gedit space break hyphen loop dot rb space ampersand.
06:33	You can pause the tutorial and type the code as we go through this example.
06:38	I have declared an each loop in this example.
06:41	It is similar to the one we used earlier.
06:43	The 'puts' method here, will display the output for numbers 11 to 19.
06:49	Once the value becomes 20, the program enters the conditional 'if' block.
06:54	At this point, it will encounter the break statement and breaks out of the loop.
06:59	Now, open the terminal and type:
07:02	ruby space break hyphen loop dot rb
07:05	and see the output.
07:08	The output will consist of numbers 10 through 19.
07:13	Now, you should be able to create your own break construct.
07:17	This brings us to the end of this Spoken Tutorial.
07:20	Let's summarize.
07:22	In this tutorial, we have learnt to use:
07:24	while loop, until construct
07:26	redo, break construct.
07:29	As an assignment-
07:31	Consider a range of numbers 100 to 115(inclusive), represented as Fahrenheit.
07:38	Write a Ruby program using
07:40	the appropriate loop construct
07:42	that uses the Fahrenheit to Celsius conversion formula
07:46	against the given range of numbers.
07:49	to display the output: “The temperature has reached a certain degree Celsius and has become unbearable”
07:55	when the temperature in Celsius is above 32 degree Celsius.
08:00	Watch the video available at the following link.
08:03	It summarizes the Spoken Tutorial project.
08:07	If you do not have good bandwidth, you can download and watch it.
08:10	The Spoken Tutorial project team:
08:13	Conducts workshops using spoken tutorials.
08:15	Gives certificates to those who pass an online test.
08:19	For more details, please write to: contact@spoken-tutorial.org
08:25	Spoken Tutorial project is a part of the Talk to a Teacher project.
08:29	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
08:35	More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
08:44	This is Anjana Nair, signing off. Thank you.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14