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 following arithmetic operators.
00:42	+Addition: eg. a+b.
00:45	- Subtraction: eg. a-b.
00:48	/ Division: eg. a/b.
00:51	* Multiplication: eg. a*b.
00:55	% Modulus: eg. a%b.
00:59	** Exponent : eg 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 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 (*) has higher precedence than the addition operator (+)
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	Lets us see some more examples based on operator precedence.
03:47	Let's go back to the terminal.
03:50	Press Crtl and 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 opertion is performed first and then subtraction is performed.
04:20	Lets us see an 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 slides.
04:54	Relational operators are also known as comparison operators.
04:59	Expressions using relational operators return boolean values.
05:04	Relation Operators in Ruby are
05:07	== Equals to Eg. a==b
05:14	dot eql question mark Eg. a.eql?b
05:21	!= Not equals to Eg. a exclamation equal b
05:28	Less than Eg. a < b
05:32	Greater than Eg. a > b
05:37	<= Lesser than or equal to Eg.a less than arrow equal b
05:44	>= Greater than or equal to Eg.a greater than arrow equal b
05:49	<=> Combined comparison Eg.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	Lets us 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	.eql? opeartor is same as equals to operator.
06:24	Lets try it out
06:25	Now type 10 .eql?10 and Press Enter
06:33	We get the output as true
06:35	Now lets 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	Let us now 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 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 comparision operator.
08:19	The combined comparision 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 astreisk 5 bracket 8 slash 2
09:32	4 astreisk 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 astreisk 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 summarises 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

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