Ruby/C2/Logical-and-other-Operators/English-timed

Time'	Narration
00.02	Welcome to this spoken tutorial on Logical & Other Operators.
00.06	In this tutorial we will learn
00.09	Logical Operators
00.11	Parallel assignment and
00.13	Range Operators
00.15	Here we are using
00.17	Ubuntu Linux version 12.04
00.20	Ruby 1.9.3
00.23	To follow this tutorial you must know how to use Terminal and Text editor in Linux.
00.29	You must also be familiar with irb
00.33	If not, for relevant tutorials, please visit our website
00.38	Logical Operators are also known as Boolean Operators
00.42	because they evaluate parts of an expression
00.45	and return a true or false value.
00.48	Logical Operators are,
00.51	double ampersand (&&) that is (and)
00.54	double pipe (	) that is (or)
00.56	Exclamation (!) that is (not)
01.00	&&(double ampersand) and and evaluate to true only if both the expressions are true.
01.07	Second expression is evaluated only if the first is true.
01.12	Difference in the two forms is, precedence
01.15	Symbolic and that is&&(double ampersand) has higher precedence.
01.20	Let's us see some examples now.
01.22	We will use irb for this.
01.25	Open the terminal by pressing Ctrl, Alt and T keys simultaneously.
01.31	Type irb and press Enter to launch interactive Ruby
01.36	Type 3 greater than 2 space double ampersand space 4 less than 5
01.47	Press Enter
01.49	We get the output as true.
01.53	Here, expression1 that is 3>2 is true.
01.59	Expression 2 that is 4<5 is also true.
02.03	Since both the expressions are true, we get output as true.
02.08	Now press Up Arrow key to get the previous command.
02.12	And replace the double ampersand symbol with the word and.
02.17	Press Enter
02.19	We get the same result.
02.22	Now press up arrow key again to get the previous command.
02.27	In expression 1 replace greater than sign with less than
02.32	Press Enter
02.35	We get the output as false.
02.38	This is because 3<2 is false.
02.43	Since the first expression is false, the second expression will not be evaluated.
02.49	So, we get output as false.
02.53		(double pipe) and or evaluate to true, if either expression is true.
02.59	Second expression is evaluated only if first is false.
03.04	Difference in the two forms is precedence.
03.07	Symbolic or i.e "	" (double pipe) has higher precedence.
03.11	Now, let's try some examples.
03.15	10 greater than 6 space double pipe space 12 less than 7
03.23	Press Enter.
03.26	We get output as true.
03.29	Here expression 1 that is 10<6 is true.
03.35	Since the first expression is true , second expression will not be evaluated.
03.40	So, we get the output as true.
03.42	Now press the Up Arrow key to get the previous command.
03.46	In expression 1 replace greater than sign with less than sign.
03.52	And replace pipe symbol with the word or.
03.57	Press Enter.
04.00	Here, expression1 that is 10<6 is false.
04.05	Expression 2 that is 12<7 is also false.
04.10	Since both the expressions are false, we get output as false.
04.15	! (exclamation mark ) and not operators return the opposite value of the expression
04.20	If the expression is true, exclamation mark operator will return a false value.
04.27	It will return true if the expression is false.
04.30	Difference in the two forms is precedence.
04.33	Symbolic not that is (!) has higher precedence.
04.37	Let's try out the not operator.
04.40	First type 10 double equal to 10
04.45	Press Enter
04.47	We get the output as true.
04.50	To invert the result of above expression,
04.53	let's add the not operator before the expression.
04.57	Type Exclamation mark within brackets 10 double equal to 10
05.04	Press Enter.
05.06	We get the output as false.
05.10	Press Ctrl+L simultaneously to clear the irb console.
05.15	Next, let us learn about parallel assignment.
05.20	Multiple variables can be initialized with a single line of Ruby code, through parallel assignment.
05.26	Let's switch to the terminal.
05.29	Let's declare three variables a, b, c using parallel assignment.
05.36	Type a comma b comma c equal to 10 comma 20 comma 30
05.45	and press Enter.
05.47	Here, 10 will be assigned to variable a
05.52	20 will be assigned to variable b
05.54	30 will be assigned to variable c
05.56	The right hand side acts as an array.
06.01	If we list multiple variables on the left hand side, then the array is unpacked and assigned into the respective variables.
06.10	We will learn about arrays in detail in the upcoming tutorials.
06.14	For now, let's check whether the assignment is done properly.
06.20	Type a and press Enter.
06.23	Value 10 stored in variable a is displayed.
06.28	Type b and press Enter.
06.31	We get 20
06.33	Type c and press Enter.
06.37	30 is displayed.
06.40	Parallel assignment is also useful for swapping the values stored in two variables.
06.45	Let us swap the values of variables a and b.
06.50	Type puts space within double quotes a equal to hash within curly brackets a comma within double quotes b equal to hash within curly brackets b
07.11	Press Enter.
07.13	We get the output as a=10
07.16	b=20
07.20	Now let's swap a and b.
07.23	To do so type
07.25	a comma b equal to b comma a
07.31	Press Enter.
07.33	Press Up Arrow key twice to get the puts command and press Enter.
07.39	We get the output as
07.41	a=20
07.44	b=10
07.47	We will now learn about range in Ruby.
07.50	The values in a range can be numbers, characters, strings or objects.
07.58	Ranges are used to express a sequence.
08.02	Sequence range is used to create a range of successive values.
08.06	It consists of a start value, range of values and an end value.
08.13	(..) two dot operator creates inclusive range.
08.16	(...) three dot operator creates an exclusive range.
08.20	Ranges are used to identify whether a value falls within a particular range, too.
08.26	We do this using (===) the equality operator.
08.30	Let us try out some examples on ranges.
08.33	Let's switch to terminal.
08.36	Type Within brackets 1 two dots 10 then dot to underscore a
08.46	Two dot operator creates inclusive range.
08.50	Inclusive operator includes both begin and end values in a range.
08.57	Here to_a method is used to convert a range to a list.
09.03	Press Enter.
09.05	Here you can see the values 1 and 10 are included in the range.
09.11	Now we will see an exclusive range operator.
09.16	Type Within brackets 1 three dots 10 then dot to underscore a
09.27	Three dot operator creates an exclusive range.
09.31	Exclusive range operator excludes the end value from the sequence.
09.37	Press Enter.
09.39	Here the end value 10 is not included in the range.
09.45	Now let's check whether 5 lies in the range of 1 to 10.
09.50	Type Within brackets 1 two dots 10 three times equal to and then 5
10.00	Press Enter.
10.02	Equality operator is used to check whether a value lies in the range.
10.07	We get the output as true since 5 lies in the range 1 to 10.
10.14	This brings us to the end of this Spoken Tutorial.
10.17	In this tutorial, we have learnt
10.20	Logical operator i.e &&,	, !(double ampersand, double pipe and exclamation mark operators)
10.27	Parallel assignment Ex: a,b,c=10,20,30
10.34	Range Operator Inclusive operator (..) and Exclusive operator(...)
10.39	As an assignment
10.41	Declare two variables using parallel assignment and
10.45	Check whether their sum lies between 20 and 50
10.49	Watch the video available at the following link.
10.52	It summarises the Spoken Tutorial project.
10.56	If you do not have good bandwidth, you can download and watch it.
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11.19	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
11.25	More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro
11.34	This script has been contributed by the spoken tutorial team IIT Bombay
11.38	And this is Shalini Nair signing off Thank you

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PoojaMoolya, Pratik kamble, Ranjana, Sandhya.np14