Difference between revisions of "Ruby/C3/while-and-until-Looping-Statements/English-timed"

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Revision as of 15:04, 10 June 2014


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
00.10 until loop
00.11 redo
00.12 and break
00.13 We are using
00.14 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 directory.
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
00.57 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 is 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
02.48 end
02.50 Let us look at an example.
02.52 Now let us switch to a 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
04.28 redo
04.29 end conditional
04.30 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.
05.53 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
06.13 break
06.14 end conditional
06.16 ruby code
06.17 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 break 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
07.25 until construct
07.26 redo
07.27 break construct
07.29 As as 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 Celcius and has become unbearable”
07.55 when the temperature in Celcius is above 32 degree Celcius
08.00 Watch the video available at the following link.
08.03 It summarises 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

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