Ruby/C2/Arithmetic-and-Relational-Operators/English

Title of script: Looping Statements

Author: Anjana Nair

Keywords: while, until, redo, break, loop, Ruby, video tutorial

Visual Cue	Narration
Slide 1	Welcome to the tutorial on while and until loops in Ruby.
Slide 2	In this tutorial we will learn to use- while loop until loop redo break
Slide 3 System Requirements	Here we are using Ubuntu version 12.04 Ruby1.9.3
Slide 4 Pre-requisites	To follow this tutorial, you must have Internet Connection. You must also have knowledge of Linux commands, Terminal and Text-editor. If not, for relevant tutorials, please visit our website.
	Before we begin, recall that we had created “ttt” directory earlier. Let's go to that directory.
Switch to the terminal window which has all the commands for creating the directories and the prompt should be in looping-statements directory	Then to ruby-tutorial and looping-statements directory.
	Now that we are in that folder, let’s move ahead.
Slide 5 “while” loop	The syntax of the while loop in Ruby is as follows: while “boolean expression” ruby code end Let us look at an example.
Switch to gedit where you have already opened the file “while-loop.rb” with the while loop code typed inside.	Create a new file in gedit as shown in the basic level Ruby tutorials. Name it while-loop.rb
	I have a working example of the while loop. You can pause the tutorial, and type the code as we go through it.
Highlight “while”	I have declared a while loop in this example.
Highlight “i = 0”	First, I declared a local variable i and initialized it with value 0.
Continue the highlight “while i >-10”	Then I declare a while loop. This loop will execute as long as the variable i is greater than -10.
Highlight “puts”	The puts method declared within the while loop will display the output.
Highlight “i -= 1”	After the output is displayed, we decrement the value of i by 1.
	i will adopt this decremented value before the next iteration.
	The variable i gets decremented in every iteration.
	This goes on till i reaches the value -10,
	At this point the while condition fails.
	It subsequently breaks out of the loop and stops printing the output.
	Now, let us switch to the terminal and type ruby while-loop.rb and see the output.
Highlight the output: The number: 0 gets printed out The number: -1 gets printed out The number: -2 gets printed out The number: -3 gets printed out The number: -4 gets printed out The number: -5 gets printed out The number: -6 gets printed out The number: -7 gets printed out The number: -8 gets printed out The number: -9 gets printed out	The output will consist of a list of numbers 0 through -9. <Pause>
	You should now be able to write your own while loop in Ruby. Let's look at the until loop next.
Slide 6 “until” loop	The syntax for the until loop in Ruby is - until “boolean expression” ruby code end Let us look at an example.
Switch to gedit where you have already opened the file “until-loop.rb” with the loop code typed inside.	Create a new file in gedit as shown in the basic level Ruby tutorials. And name it until-loop.rb
	I have a working example of the until loop. You can pause the tutorial, and type the code as we go through it.
Highlight “until”	I have declared an until loop in this example.
Highlight “i = 0”	We had declared a local variable i and initialized it to 0.
Continue the highlight “until i < -10”	Then we declare an until loop.
	This loop will execute as long as the variable i is greater than -10.
Highlight “puts”	The puts method will display the output.
Highlight “i -= 1”	After the output is displayed, value of i is decremented by 1.
	i will adopt this decremented value before the next iteration.
	The variable i gets decremented during every iteration.
	This goes on till i reaches the value -11.
	At this point the until condition fails.
	Subsequently, it breaks out of the loop and stops printing the output.
	Now switch to the terminal and type ruby until-loop.rb and see the output.
Highlight the output: The number: 0 gets printed out The number: -1 gets printed out The number: -2 gets printed out The number: -3 gets printed out The number: -4 gets printed out The number: -5 gets printed out The number: -6 gets printed out The number: -7 gets printed out The number: -8 gets printed out The number: -9 gets printed out The number: -10 gets printed out	The output will consist of a list of numbers 0 through -10. <Pause>
	You should now be able to write your own until loop in Ruby. Let's now move on to the redo construct.
Slide 7 “redo”	The syntax for redo in Ruby is as follows: (a collection of objects).each do |item| a conditional statement on an item ruby code redo end end Let us look at an example.
Switch to gedit where you have already opened the file “redo-loop.rb” with the loop code typed inside.	Create a new file in gedit as shown in the basic level Ruby tutorials, and name it redo-loop.rb
	I have a working example of the redo loop. You can pause the tutorial, and type the code as we go through it.
Highlight “each”	I have declared an each loop in this example.
i|”	We have declared an each loop to iterate through numbers 10 to 20.
Continue the highlight “if i == 20”	Then, we define an if conditional statement.
Continue the highlight	This loop will execute for every number between 10 to 20.
Continue the highlight	It will enter the inner if conditional block only if the value of i is equal to 20.
Highlight “puts”	The puts method declared within the each loop displays the output.
Continue the highlight “if i == 20”	Once the program enters the if conditional block, it will first print the output. Then it will execute redo.
	redo will execute the iteration of the most internal loop.
	It will do so without checking the loop condition. Our condition being if i == 20.
	The result will be an infinite loop, since the value of i will not change from 20.
	Let's switch to the terminal and type ruby redo-loop.rb and see the output.
Highlight the output: >ruby redo-loop.rb The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 The value has reached it's limit 20 ..................................................	The output will consist of an infinite loop that never ends. Press Ctrl + c to terminate the infinite loop <Pause>
	Next, let us look at the break statement.
Slide 8 “break” statement	The syntax for the break statement in Ruby is - a looping statement a conditional statement break end conditional end loop Let us look at an example.
Switch to gedit where you have already opened the file “break-loop.rb” with the loop code typed inside.	Create a new file in gedit as shown in the basic level Ruby tutorials. And name it break-loop.rb
	I have a working example of the break statement. You can pause the tutorial, and type the code as we go through this example.
Highlight “each”	I have declared an each loop in this example. It is similar to the one we used earlier.
Highlight “puts”	The puts method here will display the output for numbers 11 to 19.
hHighlight “if” and then "break"	Once the value becomes 20, the program enters the conditional if block. At this point, it will encounter the break statement and break out of the loop.
	Now open the terminal and type ruby break-loop.rb and see the output.
Highlight the output: >ruby break-loop.rb The value has reached it's limit 10 The value has reached it's limit 11 The value has reached it's limit 12 The value has reached it's limit 13 The value has reached it's limit 14 The value has reached it's limit 15 The value has reached it's limit 16 The value has reached it's limit 17 The value has reached it's limit 18 The value has reached it's limit 19	The output will consist of numbers 10 through 19. <Pause>
	Now you should be able to create your own break construct. <Pause>
Slide 9	<<Pause>> This brings us to the end of this Spoken Tutorial.
Slide 10 Summary	Let's summarize. In this tutorial we have learnt to use while loop until construct redo break construct
Slide 11 Assignment	As as assignment Write a Ruby program using (I have yet to come up with an assignment)
Slide 12 About the Spoken Tutorial Project	Watch the video available at the following link. It summarizes the Spoken Tutorial project. If you do not have good bandwidth, you can download and watch it.
Slide 13	The Spoken Tutorial Project Team : Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to contact at spoken hyphen tutorial dot org
Slide 14 Acknowledgements	Spoken Tutorial Project is a part of the Talk to a Teacher project. It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this Mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
Previous slide	This is Anjana Nair signing off. Thank you

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