Ruby/C2/Logical-and-other-Operators/English-timed
From Script | Spoken-Tutorial
| 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
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