Difference between revisions of "Ruby/C3/for-and-each-Looping-Statements/English-timed"
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Revision as of 12:13, 9 June 2014
| Time' | Narration |
| 00.01 | Welcome to the tutorial on for and each Loops in Ruby. |
| 00.05 | In this tutorial we will learn |
| 00.07 | Meaning of the term “loop” |
| 00.08 | The different kinds of loops in Ruby |
| 00.11 | Usage of “for” loop and |
| 00.12 | Usage of “each” looping construct |
| 00.14 | Here we are using |
| 00.16 | Ubuntu version 12.04 |
| 00.19 | Ruby 1.9.3 |
| 00.22 | To follow this tutorial, you must have Internet Connection.
|
| 00.25 | 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 | Now let me explain what is referred to as a “loop” in Ruby. |
| 00.38 | A loop is a command or set of commands that are executed a fixed number of times. |
| 00.44 | Ruby has the following main looping statements. |
| 00.47 | for |
| 00.48 | each |
| 00.49 | while |
| 00.49 | until |
| 00.50 | In this tutorial we will learn how to use the for and each looping constructs. |
| 00.55 | Before we begin, please create the following folders in your home directory, |
| 01.02 | ttt, ruby hyphen tutorial, looping hyphen statements. |
| 01.07 | Please create the sub folders as mentioned there |
| 01.11 | Now we have created the requisite folders. |
| 01.13 | Let's move ahead. |
| 01.15 | The syntax of the “for” loop in Ruby is as follows:
|
| 01.19 | for “variable” in “a collection of objects”
|
| 01.22 | ruby code |
| 01.23 | end |
| 01.25 | Let us try to understand it with an example. |
| 01.28 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
| 01.32 | And name it “for hyphen loop dot rb”
|
| 01.36 | I already have a working example of the “for” loop. |
| 01.39 | You can type the code as we go through this example. |
| 01.44 | I have declared a “for” loop in this example. |
| 01.47 | We have a set of numbers 1 to 20. |
| 01.50 | We declare a variable called “i” within the “for” loop.
|
| 01.55 | The variable “i” gets initialized to the first element in the set of numbers 1 to 20. |
| 02.00 | The “for” loop declaration causes the code to iterate over each element in the set 1 to 20. |
| 02.07 | The “puts” method declared within the “for” loop is responsible for generating the output.
|
| 02.14 | Now open the terminal and type |
| 02.17 | “ruby space for hyphen loop dot rb” and see the output |
| 02.22 | The output will be an array of numbers 1 to 20. |
| 02.26 | In this example, we declared a “for” loop for an inclusive range. |
| 02.31 | It included all numbers from 1 to 20. |
| 02.35 | Next, we shall look at implementing the “for” loop for a non-inclusive range. |
| 02.41 | Continue to type the next part of the code. |
| 02.44 | Non-inclusive means it will not include the last element in the collection of objects. |
| 02.49 | Here “for” loop is implemented for a non-inclusive range of numbers 1 to 20. |
| 02.55 | You will notice shortly that the number 20 will not be printed in the output. |
| 02.59 | The last digit does not get included when you have 3 dots between numbers. |
| 03.04 | Now open the terminal and type ruby space for hyphen loop dot rb |
| 03.13 | and see the output. |
| 03.17 | The output will still be an array of numbers but will not include the number 20.
|
| 03.22 | Now, you should be capable enough to write your own “for” loop. |
| 03.27 | The syntax of the “each” loop in Ruby is as follows: |
| 03.31 | “a collection of objects” dot each do item |
| 03.36 | ruby code end |
| 03.38 | Let us try to understand it with an example.
|
| 03.42 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
| 03.46 | And name it each hyphen loop dot rb |
| 03.50 | I already have a working example of the each loop. |
| 03.53 | You can type the code as we go through this example. |
| 03.58 | I have declared an each loop in this example. |
| 04.03 | We have a set of numbers 1 to 20. |
| 04.06 | We declare a variable called “i” within the each loop.
|
| 04.11 | The “i” variable gets initialized to the first element in the set of numbers 1 to 20.
|
| 04.17 | The each loop declaration causes the code to iterate over each element in the set 1 to 20. |
| 04.23 | The puts method declared within the each is responsible for generating the output. |
| 04.30 | Now open the terminal and type ruby space each hyphen loop dot rb |
| 04.39 | and see the output.
|
| 04.43 | The output will be an array of numbers 1 to 20.
|
| 04.46 | In the above example we declared an each loop for an inclusive range.
|
| 04.51 | It included all numbers from 1 to 20. |
| 04.54 | Next we shall look at implementing the each loop for a non-inclusive range. |
| 05.00 | Continue to type this part of the code. |
| 05.04 | Non-inclusive means it will not include the last element in the collection of objects. |
| 05.10 | Here an each loop is implemented for a non-inclusive range of numbers 1 to 20.
|
| 05.16 | You will notice shortly that the number 20 will not be printed in the output. |
| 05.20 | The last digit does not get included when you have 3 dots between numbers. |
| 05.25 | Now open the terminal and type ruby space each hyphen loop dot rb |
| 05.34 | and see the output. |
| 05.39 | Now you should be capable enough to write your own each loop. |
| 05.44 | How would we determine which looping construct to choose? |
| 05.48 | Let us try to recall the for loop construct.
|
| 05.53 | In the first example, we iterated over a set of numbers from 1 to 20 using for. |
| 05.59 | Execute ruby space for hyphen loop dot rb in your terminal see the output. |
| 06.08 | Now look at the code in gedit. |
| 06.11 | When you invoke the for loop, Ruby is actually calling the each method behind the scenes. |
| 06.16 | And calling each or for will generate the same output. |
| 06.21 | Since the call to for in turn calls each, it is preferable to use the each loop instead. |
| 06.28 | This brings us to the end of this Spoken Tutorial.
|
| 06.30 | Let's summarize.
|
| 06.32 | In this tutorial we have learnt |
| 06.33 | Usage of for loop |
| 06.35 | Usage of each construct |
| 06.38 | Reasoning behind using each instead of for |
| 06.41 | Examples of using the above looping constructs |
| 06.45 | As an assignment |
| 06.47 | Write a ruby program using the appropriate loop construct |
| 06.50 | to create an output of even numbers from a set of numbers, say 1 to 20
|
| 06.56 | Watch the video available at the following link. |
| 07.00 | It summarises the Spoken Tutorial project. |
| 07.03 | If you do not have good bandwidth, you can download and watch it. |
| 07.08 | The Spoken Tutorial Project Team : |
| 07.11 | Conducts workshops using spoken tutorials |
| 07.14 | Gives certificates to those who pass an online test |
| 07.18 | For more details, please write to contact@spoken-tutorial.org |
| 07.23 | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
| 07.26 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 07.33 | More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro |
| 07.41 | This is Anjana Nair signing off. Thank you |
