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

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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.
11:00 The Spoken Tutorial Project Team :
11:03 Conducts workshops using spoken tutorials
11:05 Gives certificates to those who pass an online test
11:09 For more details, please write to contact@spoken-tutorial.org
11:15 Spoken Tutorial Project is a part of the Talk to a Teacher project.
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


Contributors and Content Editors

PoojaMoolya, Pratik kamble, Ranjana, Sandhya.np14