Difference between revisions of "Ruby/C2/Logical-and-other-Operators/English-timed"
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|You must also be familiar with '''irb''' | |You must also be familiar with '''irb''' | ||
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| If not, for relevant tutorials, please visit our website | | If not, for relevant tutorials, please visit our website | ||
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|We will use '''irb''' for this. | |We will use '''irb''' for this. | ||
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| Type ''' 3 greater than 2 space double ampersand space 4 less than 5''' | | Type ''' 3 greater than 2 space double ampersand space 4 less than 5''' | ||
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| − | | | + | |Since both the expressions are '''true''', we get output as '''true.''' |
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| − | | | + | | And ''' replace the double ampersand''' symbol with the word ''' and.''' |
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| In ''' expression 1''' replace '''greater than''' sign with '''less than''' | | In ''' expression 1''' replace '''greater than''' sign with '''less than''' | ||
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|Second expression is evaluated only if first is '''false.''' | |Second expression is evaluated only if first is '''false.''' | ||
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|So, we get the output as '''true. ''' | |So, we get the output as '''true. ''' | ||
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| let's add the '''not''' operator before the expression. | | let's add the '''not''' operator before the expression. | ||
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|Type '''Exclamation mark within brackets 10 double equal to 10 ''' | |Type '''Exclamation mark within brackets 10 double equal to 10 ''' | ||
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| Press '''Enter. ''' | | Press '''Enter. ''' | ||
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|'''30''' will be assigned to variable '''c ''' | |'''30''' will be assigned to variable '''c ''' | ||
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|30 is displayed. | |30 is displayed. | ||
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| '''Parallel assignment''' is also useful for swapping the values stored in two variables. | | '''Parallel assignment''' is also useful for swapping the values stored in two variables. | ||
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| '''b=10 ''' | | '''b=10 ''' | ||
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|Type '''Within brackets 1 two dots 10 then dot to underscore a ''' | |Type '''Within brackets 1 two dots 10 then dot to underscore a ''' | ||
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|Here the end value 10 is not included in the range. | |Here the end value 10 is not included in the range. | ||
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|Type '''Within brackets 1 two dots 10 three times equal to and then 5 ''' | |Type '''Within brackets 1 two dots 10 three times equal to and then 5 ''' | ||
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|In this tutorial, we have learnt | |In this tutorial, we have learnt | ||
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|Check whether their sum lies between 20 and 50 | |Check whether their sum lies between 20 and 50 | ||
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|And this is Shalini Nair signing off Thank you | |And this is Shalini Nair signing off Thank you | ||
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Revision as of 16:49, 5 May 2015
| 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 |
