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

Time	Narration
00:01	Welcome to the Spoken Tutorial on Arithmetic & Relational Operators in Ruby.
00:06	In this tutorial, we will learn about:
00:08	* Arithmetic Operators
00:10	* Operator Precedence
00:12	* Relational Operators.
00:14	Here we are using: Ubuntu Linux version 12.04 Ruby 1.9.3
00:23	To follow this tutorial, you must know how to use Terminal and Text editor in Linux.
00:28	You must also be familiar with 'irb'.
00:31	If not, for relevant tutorials, please visit our website.
00:34	Now, let us learn about arithmetic operators.
00:38	Ruby has the following arithmetic operators.
00:42	* '+' Addition, e.g. a+b.
00:45	* '-' Subtraction, e.g. a-b.
00:48	* '/' Division, e.g. a/b.
00:51	* '*' Multiplication, e.g. a*b.
00:55	* '%' Modulus, e.g. a%b.
00:59	* '**' Exponent, e.g. a**b.
01:04	Let us try these arithmetic operators using irb.
01:08	Open the terminal by pressing Ctrl, Alt and T keys simultaneously.
01:14	A terminal window appears on your screen.
01:17	Type "irb" and press Enter to launch the interactive Ruby.
01:21	Type: 10 plus 20 and press Enter.
01:25	The addition operation is performed and the result 30 is displayed.
01:31	Similarly, the subtraction and multiplication operations can be performed.
01:35	Let us try the division operator.
01:38	Type: 10 slash 4
01:40	and press Enter.
01:42	Here you can see the result is truncated to the nearest whole number which is 2.
01:47	To get a more accurate answer, we need to express one number as float.
01:52	Type: 10.0 slash 4
01:56	and press Enter.
01:58	Now we get the result as 2.5.
02:01	Let's now try the modulus operator.
02:05	The modulus operator returns the remainder as output.
02:09	Type: 12 percentage sign 5 and press Enter.
02:15	Here, 12 is divided by 5 and the remainder 2 is returned back.
02:21	Now, let's try the exponent operator.
02.24	Type: 2 followed by the asterisk symbol twice and then 5 and press Enter.
02:32	This means that 2 is raised to the power of 5.
02:36	So, we get the output as 32.
02:39	Next, let us learn about operator precedence.
02:44	When several operations occur in a mathematical expression,
02:47	each part is evaluated
02:50	and resolved in a predetermined order called operator precedence.
02:56	This means that the operator which has the highest priority is executed first.
03:01	This is then followed by the next operator in the priority order and so on.
03:07	This slide lists all operators from highest precedence to lowest.
03:13	For example, 3 + 4 * 5 returns 23 and not 35.
03:23	The multiplication operator asterisk (*) has higher precedence than the addition operator plus (+)
03:29	and thus will be evaluated first.
03:32	Hence, four fives are twenty and then three is added to 20 to give the output as 23.
03:42	Let's see some more examples based on operator precedence.
03:47	Let's go back to the terminal and
03:50	press Crtl, L keys simultaneously to clear the irb console.
03:56	Now, type: 7 minus 2 multiply by 3
04:03	and press Enter .
04:05	We get the answer as 1.
04:08	Here, the asterisk symbol has higher priority than the minus sign.
04:13	So, the multiplication operation is performed first and then subtraction is performed.
04:20	Let's see another example.
04:22	Type: within brackets 10 plus 2 slash 4
04:29	and press Enter.
04:30	We get the answer as 3.
04:33	In this case, () bracket has the higher priority than division (slash).
04:39	So, the operation inside the bracket, that is addition, is performed first.
04:44	Then division is performed.
04:47	Now, let us learn about Relational Operators.
04:51	Let's switch back to the slides.
04:54	Relational operators are also known as comparison operators.
04:59	Expressions using relational operators return boolean values.
05:04	Relational operators in Ruby are-
05:07	* == Equals to, e.g. a==b
05:14	* dot eql question mark e.g. a.eql?b
05:21	* != Not equals to e.g. a exclamation equals b
05:28	* < Less than e.g. a < b
05:32	* > Greater than e.g. a > b
05:37	* <= Lesser than or equal to e.g. a less than arrow equals b
05:44	* >= Greater than or equal to e.g. a greater than arrow equals b
05:49	* <=> Combined comparison e.g. a less than arrow equal greater than arrow b.
05:56	Now let us try some of these operators.
06:00	Go to the terminal.
06:02	Press ctrl, L keys simultaneously to clear the irb console.
06:09	Let's try equals to operator.
06:11	So, type: 10 equals equals 10
06:16	and press Enter.
06:17	We get the output as "true".
06:20	The .eql? opeartor is same as equals to operator.
06:24	Let's try it out.
06:25	Now, type 10 .eql?10 and press Enter.
06:33	We get the output as "true".
06:35	Now, let's try not equal to operator.
06:39	Type: 10 not equal 10
06:44	and press Enter.
06:46	We get the output as "false".
06:48	This is because the two numbers are equal.
06:51	Clear the irb console by pressing Ctrl, L simultaneously.
06:56	Now, let us try less than operator.
07:00	Type: 10 less than 5 and press Enter.
07:05	Here, if first operand is less than second then it will return "true".
07:10	Otherwise, it will return "false".
07:14	We get the output as "false" because 10 is not less than 5.
07:19	We will now try greater than operator.
07:22	Type: 5 greater than 2.
07:26	Here, if first operand is greater than second then it will return "true";
07:31	otherwise it will return "false".
07:34	Press Enter.
07:36	In this case, we get the output as "true" because 5 is indeed greater than 2.
07:42	Clear the irb console by pressing Ctrl, L simultaneously.
07:47	We will now try the less than equal to operator.
07:51	Type: 12 less than equal 12
07:56	and press Enter.
07:59	Here, if first operand is less than or equal to the second then it returns "true";
08:04	otherwise it returns "false".
08:07	We get the output as "true" because 12 is equal to 12.
08:11	You can try out the greater than or equal to operator likewise.
08:15	Now, let's try the combined comparison operator.
08:19	The combined comparison operator:
08:21	* Returns 0 if first operand equals second
08:24	* Returns 1 if first operand is greater than the second and
08:29	* Returns -1 if first operand is less than the second operand.
08:34	Let's see how it works, with an example.
08:36	Type: 3 less than equals greater than 3
08:41	and press Enter.
08:43	We get the output as 0
08:45	because both the operands are equal i.e. both are three.
08:50	Now, let's change one of the operands to 4.
08:53	Type: 4 less than equals greater than 3
08:58	and press Enter.
08:59	We get the output as 1
09:01	since 4 is greater than 3.
09:04	Now, let's change this example again.
09:07	Type: 4 less than equals greater than 7
09:11	and press Enter .
09:13	We get the output as -1
09:14	since 4 is less than 7.
09:17	As an assignment,
09:19	solve the following examples using irb and check the output:
09:24	* 10 + bracket 2 asterisk 5 bracket 8 slash 2
09:32	* 4 asterisk 5 slash 2 plus 7
09:37	Also, try arithmetic operators using methods.
09:42	This brings us to the end of this Spoken Tutorial.
09:45	Let's summarize..
09:47	In this tutorial, we have learnt about:
09:49	* Arithmetic Operators- plus, minus, asterisk, slash standing for addition, subtraction, multiplication, division.
09:59	* Operator Precedence
10:01	* Relational Operators
10:04	using many examples.
10:06	Watch the video available at the following link.
10:10	It summarizes the Spoken Tutorial project.
10:14	If you do not have good bandwidth, you can download and watch it.
10:18	The Spoken Tutorial project team:
10:20	* Conducts workshops using spoken tutorials.
10:23	* Gives certificates to those who pass an online test.
10:26	For more details, please write to: contact@spoken-tutorial.org
10:32	Spoken Tutorial project is a part of the Talk to a Teacher project.
10:36	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:43	More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
10:51	This script has been contributed by the spoken tutorial team, IIT Bombay.
10:57	And this is Anjana Nair, signing off. Thank you.

Contributors and Content Editors

Devraj, PoojaMoolya, Pratik kamble, Sandhya.np14, Shruti arya