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− | || ''Time''' | + | || '''Time''' |
|| '''Narration''' | || '''Narration''' | ||
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− | | 00 | + | | 00:01 |
− | | Welcome to the spoken tutorial on Control Statements in ''' Ruby.''' | + | | Welcome to the '''spoken tutorial''' on '''Control Statements''' in '''Ruby.''' |
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− | | 00 | + | | 00:06 |
− | | In this tutorial we will learn to use | + | | In this tutorial, we will learn to use: |
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− | | 00 | + | | 00:08 |
− | | ''' if statement ''' | + | | ''''if'''' statement , ''''elsif'''' statement |
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− | | 00 | + | | 00:11 |
− | |''' | + | | ''''else''', ''''case'''' statements. |
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− | | 00 | + | | 00:14 |
− | | ''' | + | |Here we are using: '''Ubuntu''' version '''12.04''' |
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− | | | + | | 00:18 |
− | |''' | + | |''' Ruby 1.9.3'''. |
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− | | | + | | 00:21 |
− | + | |To follow this tutorial, you must have ''' Internet''' connection. | |
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− | |To follow this tutorial, you must have ''' Internet''' | + | |
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− | | 00 | + | | 00:24 |
− | | You must also have knowledge of '''Linux''' | + | | You must also have knowledge of '''Linux''' commands, ''' Terminal''' and ''' Text-editor.''' |
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− | | 00 | + | | 00:30 |
|If not, for relevant tutorials, please visit our website. | |If not, for relevant tutorials, please visit our website. | ||
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− | | 00 | + | | 00:34 |
− | | Before we begin, recall that we had created ''' “ttt” ''' directory earlier. | + | | Before we begin, recall that we had created '''“ttt”''' directory earlier. |
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− | | 00 | + | | 00:38 |
|Let's go to that directory. | |Let's go to that directory. | ||
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− | | 00 | + | | 00:41 |
− | |Then to ''' ruby hyphen tutorial''' | + | |Then to '''ruby hyphen tutorial''' '''control hyphen statements'''. |
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− | | 00 | + | | 00:47 |
|Now that we are in that folder, let’s move ahead. | |Now that we are in that folder, let’s move ahead. | ||
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− | | 00 | + | | 00:52 |
− | | The syntax of the ''' if statement''' in | + | | The syntax of the ''''if' statement''' in Ruby is as follows: |
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− | | | + | | 00:56 |
− | | | + | |'''if “condition” ''' |
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− | | 00 | + | | 00:58 |
− | |'''end''' | + | | ''' ruby code'''. '''end''' |
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− | | 01 | + | | 01:01 |
| Let us look at an example. | | Let us look at an example. | ||
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− | | 01 | + | | 01:03 |
− | |Create a new file in ''' gedit''' as shown in the basic level '''Ruby''' | + | |Create a new file in ''' gedit''' as shown in the basic level '''Ruby tutorials'''. |
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− | | 01 | + | | 01:08 |
− | |Name it ''' if hyphen statement dot rb''' | + | |Name it '''if hyphen statement dot rb'''. |
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− | | 01 | + | | 01:12 |
− | |I have a working example of the ''' if | + | |I have a working example of the ''' if''' statement. |
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− | | 01 | + | | 01:15 |
− | | You can pause the tutorial | + | | You can pause the tutorial and type the code as we go through it. |
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− | | 01 | + | | 01:19 |
− | |I have declared an ''' if statement''' in this example. | + | |I have declared an '''if statement''' in this example. |
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− | | 01 | + | | 01:23 |
| First, I declare a local variable ''' my_num''' and assign the value 2345 to it. | | First, I declare a local variable ''' my_num''' and assign the value 2345 to it. | ||
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− | | 01 | + | | 01:31 |
− | | Then I declare an ''' if''' statement. | + | | Then I declare an '''if''' statement. |
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− | | 01 | + | | 01:34 |
| The '''puts''' method declared within the '''if''' statement will display the output. | | The '''puts''' method declared within the '''if''' statement will display the output. | ||
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− | | 01 | + | | 01:39 |
− | |The '''if | + | |The '''if''' statement will check if the value of ''' my_num''' is greater than 0. |
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− | | 01 | + | | 01:43 |
|If it is, it will print out the specified ''' string.''' | |If it is, it will print out the specified ''' string.''' | ||
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− | | 01 | + | | 01:47 |
− | |Now, let us switch to the '''terminal''' and type | + | |Now, let us switch to the '''terminal''' and type: |
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− | | 01 | + | | 01:51 |
− | | ''' ruby space | + | | '''ruby space if hyphen statement dot rb'''. |
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− | | 01 | + | | 01:57 |
| The output will display ''' “The value of my_num is greater than 0”.''' | | The output will display ''' “The value of my_num is greater than 0”.''' | ||
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− | | 02 | + | | 02:02 |
| This output proves that the '''if''' condition returned '''true.''' | | This output proves that the '''if''' condition returned '''true.''' | ||
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− | | 02 | + | | 02:07 |
− | |You should now be able to write your own ''' if statement''' in | + | |You should now be able to write your own ''' 'if' statement''' in Ruby. |
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− | | 02 | + | | 02:12 |
− | | Let's look at the ''' if-else statement''' next. | + | | Let's look at the ''' 'if-else' statement''' next. |
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− | | 02 | + | | 02:16 |
| The syntax for using '''else''' is: | | The syntax for using '''else''' is: | ||
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− | | 02 | + | | 02:18 |
− | |''' | + | |''' if “condition” ''', ''' ruby code''' |
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− | | | + | | 02:20 |
− | | '''ruby code ''' | + | |'''else''', '''ruby code ''' |
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− | | 02 | + | | 02:22 |
| ''' end''' | | ''' end''' | ||
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− | | 02 | + | | 02:24 |
| Let us look at an example. | | Let us look at an example. | ||
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− | | 02 | + | | 02:26 |
− | |Create a new file in ''' gedit''' as shown in the basic level ''' Ruby''' | + | |Create a new file in ''' gedit''' as shown in the basic level ''' Ruby tutorials'''. |
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− | | 02 | + | | 02:30 |
− | |Name it ''' if hyphen else hyphen statement dot rb''' | + | |Name it '''if hyphen else hyphen statement dot rb'''. |
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− | | 02 | + | | 02:37 |
− | |I have a working example of the ''' if-else statement.''' | + | |I have a working example of the ''' 'if-else' statement.''' |
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− | | 02 | + | | 02:40 |
− | | You can pause the tutorial | + | | You can pause the tutorial and type the code as we go through it. |
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− | | 02 | + | | 02:44 |
− | |I have declared an ''' if-else statement''' in this example. | + | |I have declared an '''if-else statement''' in this example. |
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− | | 02 | + | | 02:48 |
| First I declare a local variable ''' my_num''' and assign the value of -1 to it. | | First I declare a local variable ''' my_num''' and assign the value of -1 to it. | ||
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− | | 02 | + | | 02:55 |
|Then I declare an '''if''' statement. | |Then I declare an '''if''' statement. | ||
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− | | 02 | + | | 02:58 |
− | |The '''if''' statement will check if the value of | + | |The ''''if'''' statement will check if the value of 'my_num' is greater than 0. |
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− | | 03 | + | | 03:03 |
| If it is, it will print out the specified '''string.''' | | If it is, it will print out the specified '''string.''' | ||
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− | | 03 | + | | 03:06 |
|If not, it will go to the '''else''' statement. | |If not, it will go to the '''else''' statement. | ||
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− | | 03 | + | | 03:10 |
| And it will print out the ''' string''' that is specified there. | | And it will print out the ''' string''' that is specified there. | ||
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− | | 03 | + | | 03:13 |
− | | Now, let us switch to the '''terminal''' and type | + | | Now, let us switch to the '''terminal''' and type: |
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− | | 03 | + | | 03:18 |
|'''ruby space if hyphen else hyphen statement dot rb''' | |'''ruby space if hyphen else hyphen statement dot rb''' | ||
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− | | 03 | + | | 03:26 |
− | |The output will display ''' “The value of my_num is lesser than 0”.''' | + | | and see the output.The output will display ''' “The value of my_num is lesser than 0”.''' |
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− | | 03 | + | | 03:32 |
| This shows that the ''' else statement''' was executed. | | This shows that the ''' else statement''' was executed. | ||
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− | | 03 | + | | 03:35 |
− | | You should now be able to write your own ''' if-else statement''' in | + | | You should now be able to write your own ''' if-else statement''' in Ruby. |
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− | | 03 | + | | 03:41 |
|Let's look at the ''' if-elsif statement''' next. | |Let's look at the ''' if-elsif statement''' next. | ||
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− | | 03 | + | | 03:45 |
| The syntax for using ''' elsif''' is: | | The syntax for using ''' elsif''' is: | ||
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− | | 03 | + | | 03:48 |
|''' if “condition” ''' ''' ruby code''' | |''' if “condition” ''' ''' ruby code''' | ||
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− | | 03 | + | | 03:50 |
| ''' elsif “condition” ''' ''' ruby code''' | | ''' elsif “condition” ''' ''' ruby code''' | ||
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− | | 03 | + | | 03:52 |
|'''else''' ''' ruby code''' | |'''else''' ''' ruby code''' | ||
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− | | 03 | + | | 03:54 |
− | |'''end ''' | + | |'''end '''. Let us look at an example. |
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− | | 03 | + | | 03:58 |
− | | | + | | Create a new file in '''gedit''' as shown in the basic level '''Ruby tutorials'''. |
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− | | | + | | 04:01 |
− | | | + | |Name it ''' if hyphen elsif hyphen statement dot rb'''. |
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− | + | | 04:07 | |
− | + | | I have a working example of the '''if-elsif''' statement. | |
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− | | 04 | + | |
− | | I have a working example of the ''' if-elsif | + | |
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− | | 04 | + | | 04:10 |
− | |You can pause the tutorial | + | |You can pause the tutorial and type the code as we go through it. |
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− | | 04 | + | | 04:14 |
| I have declared an '''if-elsif statement''' in this example. | | I have declared an '''if-elsif statement''' in this example. | ||
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− | | 04 | + | | 04:19 |
− | |Here also, I have | + | |Here also, I have declared a local variable '''my_num''' and assigned the value -1 to it. |
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− | | 04 | + | | 04:25 |
|Then I declare an ''' if statement. ''' | |Then I declare an ''' if statement. ''' | ||
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− | | 04 | + | | 04:28 |
| The ''' if statement ''' will check if the value of '''my_num''' is greater than 0. | | The ''' if statement ''' will check if the value of '''my_num''' is greater than 0. | ||
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− | | 04 | + | | 04:32 |
− | | If it is, it will print out the specified string. | + | | If it is, it will print out the specified '''string'''. |
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− | | 04 | + | | 04:35 |
− | | If this is not ''' true''' , it will go into the '''elsif''' section. | + | | If this is not ''' true''', it will go into the '''elsif''' section. |
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− | | 04 | + | | 04:39 |
| It will now check if the value of ''' my_num''' is equal to -1. | | It will now check if the value of ''' my_num''' is equal to -1. | ||
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− | | 04 | + | | 04:43 |
− | |If it is true, it will print out the string that is specified there. | + | |If it is true, it will print out the '''string''' that is specified there. |
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− | | 04 | + | | 04:46 |
− | | | + | | If the value of '''my_num''' is neither greater than 0 nor equal to -1, it will go into the '''else''' section. |
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− | | 04 | + | | 04:54 |
− | |But since the value of '''my_num = -1''' it will not proceed to the else block. | + | |But, since the value of '''my_num = -1''' it will not proceed to the '''else''' block. |
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− | | 05 | + | | 05:00 |
− | |And it will exit the ''' conditional statement.''' | + | |And, it will exit the ''' conditional statement.''' |
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− | | 05 | + | | 05:03 |
− | |Now, let us switch to the ''' terminal''' and type | + | |Now, let us switch to the ''' terminal''' and type: |
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− | | 05 | + | | 05:07 |
|''' ruby space if hyphen elsif hyphen statement dot rb''' | |''' ruby space if hyphen elsif hyphen statement dot rb''' | ||
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− | | 05 | + | | 05:15 |
| and see the output. | | and see the output. | ||
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− | |05 | + | |05:17 |
| The output will display ''' “The value of my_num is -1 and is lesser than 0”.''' | | The output will display ''' “The value of my_num is -1 and is lesser than 0”.''' | ||
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− | | 05 | + | | 05:23 |
|Let's go back to our file and change the value of '''my_num''' to 5. | |Let's go back to our file and change the value of '''my_num''' to 5. | ||
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− | | 05 | + | | 05:29 |
− | |Let's save the code and execute it on the terminal. | + | |Let's '''save''' the code and '''execute''' it on the '''terminal'''. |
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− | | 05 | + | | 05:35 |
− | |So, now it fulfills the if condition and the specified string is printed. | + | |So, now it fulfills the '''if''' condition and the specified '''string''' is printed. |
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− | | 05 | + | | 05:42 |
− | | The value of ''' my_num''' is greater than 0 | + | | '''"The value of ''' my_num''' is greater than 0"'''. |
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− | | 05 | + | | 05:45 |
− | |Let's go back to our file and change the value of ''' my_num''' to -5 | + | |Let's go back to our file and change the value of ''' my_num''' to -5. |
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− | | 05 | + | | 05:50 |
− | | | + | |Let's '''save''' the code and execute it on the terminal. |
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− | | 05 | + | | 05:55 |
− | | In this case it fulfills the ''' else''' condition and the puts statement within the else block gets executed. | + | | In this case, it fulfills the ''' else''' condition and the '''puts''' statement within the '''else''' block gets executed. |
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− | | 06 | + | | 06:03 |
− | |You should now be able to write your own ''' if- elsif''' statement in | + | |You should now be able to write your own ''' if-elsif''' statement in Ruby. |
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− | | 06 | + | | 06:08 |
− | |Let us look at the ''' case statement''' next. | + | |Let us look at the ''''case' statement''' next. |
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− | | 06 | + | | 06:12 |
− | | The ''' case statement''' is a ''' control flow statement''' based on a particular selection. | + | | The ''''case' statement''' is a ''' control flow statement''' based on a particular selection. |
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− | | 06 | + | | 06:17 |
− | | Let us look at the syntax of the '''case statement''' in order to understand this statement. | + | | Let us look at the syntax of the ''''case' statement''' in order to understand this statement. |
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− | | 06 | + | | 06:22 |
|The syntax for using '''case''' is: | |The syntax for using '''case''' is: | ||
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− | | 06 | + | | 06:24 |
− | |''' case | + | |'''case''' variable |
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− | | 06 | + | | 06:26 |
− | | | + | | when “value 1” |
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− | | 06 | + | | 06:28 |
− | |'''ruby code ''' | + | |'''ruby code '''. when “value 2” '''ruby code ''' |
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− | | 06 | + | | 06:31 |
− | |''' | + | | '''else''' ''' ruby code '''. '''end'''. |
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− | | 06 | + | | 06:35 |
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|Let us look at an example. | |Let us look at an example. | ||
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− | | 06 | + | | 06:37 |
− | |Create a new file in ''' gedit''' as shown in the basic level '''Ruby''' | + | |Create a new file in ''' gedit''' as shown in the basic level '''Ruby tutorials'''. |
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− | | 06 | + | | 06:41 |
− | |Name it '''case hyphen statement dot rb''' | + | |Name it '''case hyphen statement dot rb'''. |
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− | | 06 | + | | 06:44 |
− | |I have a working example of the '' | + | |I have a working example of the 'case' statement. |
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− | | 06 | + | | 06:48 |
− | |You can pause the tutorial | + | |You can pause the tutorial and type the code as we go through it. |
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− | | 06 | + | | 06:52 |
− | |I have declared | + | |I have declared a '''case''' statement in this example. |
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− | | 06 | + | | 06:55 |
− | |Here I have a | + | |Here, I have a print statement which will print a question on the terminal. |
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− | | 07 | + | | 07:01 |
− | |Then I call a '''gets''' | + | |Then I call a '''gets''' which will accept a single line of data from the '''standard input'''. |
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− | | 07 | + | | 07:09 |
|Then I strip the input data of any '''new line characters''' using '''chomp.''' | |Then I strip the input data of any '''new line characters''' using '''chomp.''' | ||
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− | | 07 | + | | 07:15 |
|I assign the result to a variable named '''domain.''' | |I assign the result to a variable named '''domain.''' | ||
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− | | 07 | + | | 07:18 |
− | |Then I declare a case statement. | + | |Then I declare a '''case''' statement. |
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− | | 07 | + | | 07:22 |
− | |Within that I declare a '''when | + | |Within that, I declare a '''when''' statement . |
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− | | 07 | + | | 07:25 |
− | |This checks whether the specified string matches value of ''' domain | + | |This checks whether the specified '''string''' matches the value of ''' domain'''. |
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− | | 07 | + | | 07:30 |
− | |First it checks whether the value of '''domain''' is ''' “UP”. ''' | + | |First, it checks whether the value of '''domain''' is '''“UP”.''' |
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− | | 07 | + | | 07:34 |
− | |If it is so, it will print out ''' “Uttar Pradesh” ''' and exit the '''case | + | |If it is so, it will print out ''' “Uttar Pradesh” ''' and exit the '''case''' statement. |
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− | | 07 | + | | 07:39 |
|If '''domain''' is not ''' “UP”''', it checks whether the value of ''' domain''' is ''' “MP”.''' | |If '''domain''' is not ''' “UP”''', it checks whether the value of ''' domain''' is ''' “MP”.''' | ||
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− | | 07 | + | | 07:44 |
|If it is so, it will print out ''' “Madhya Pradesh” ''' and so on. | |If it is so, it will print out ''' “Madhya Pradesh” ''' and so on. | ||
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− | | 07 | + | | 07:48 |
|It will continue checking the value of ''' domain''' if no match was found so far. | |It will continue checking the value of ''' domain''' if no match was found so far. | ||
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− | | 07 | + | | 07:53 |
− | |At this point it will encounter the ''' else | + | |At this point, it will encounter the ''' else''' statement |
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− | | 07 | + | | 07:56 |
− | |as none of the above conditions were true. | + | |as none of the above conditions were '''true'''. |
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− | | 07 | + | | 07:59 |
− | |It will subsequently execute the | + | |It will subsequently execute the ruby code that follows the '''else''' declaration. |
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− | | 08 | + | | 08:03 |
|It will print ''' “Unknown”''' as per our example. | |It will print ''' “Unknown”''' as per our example. | ||
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− | | 08 | + | | 08:07 |
− | |Now, save the file | + | |Now, save the file. Switch to the ''' terminal''' and type: |
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− | | 08 | + | | 08:11 |
|''' ruby space case hyphen statement dot rb.''' | |''' ruby space case hyphen statement dot rb.''' | ||
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− | | 08 | + | | 08:18 |
|''' “Enter the state you live in:”''' will be displayed on the '''terminal.''' | |''' “Enter the state you live in:”''' will be displayed on the '''terminal.''' | ||
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− | | 08 | + | | 08:22 |
|Type in ''' “UP”''' and see the output. | |Type in ''' “UP”''' and see the output. | ||
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− | | 08 | + | | 08:25 |
|The output will display ''' “Uttar Pradesh”.''' | |The output will display ''' “Uttar Pradesh”.''' | ||
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− | | 08 | + | | 08:28 |
− | |Next execute the | + | |Next, execute the Ruby file again, like before. |
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− | | 08 | + | | 08:31 |
− | |This time at the prompt type ''' “KL”''' and see the output. | + | |This time, at the prompt, type: ''' “KL”''' and see the output. |
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− | | 08 | + | | 08:36 |
|It will print ''' “Kerala”.''' | |It will print ''' “Kerala”.''' | ||
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− | | 08 | + | | 08:38 |
− | |Next execute the file one more time. | + | |Next, execute the file one more time. |
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− | | 08 | + | | 08:41 |
− | |This time at the prompt type in ''' “TN”''' and see the output. | + | |This time, at the prompt, type in ''' “TN”''' and see the output. |
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− | | 08 | + | | 08:47 |
|It will print ''' “Unknown”.''' | |It will print ''' “Unknown”.''' | ||
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− | | 08 | + | | 08:50 |
|This is because none of the ''' cases''' were satisfied. So, the default '''else statement''' is executed. | |This is because none of the ''' cases''' were satisfied. So, the default '''else statement''' is executed. | ||
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− | | 08 | + | | 08:58 |
− | |You should now be able to write your own ''' case-statements''' in | + | |You should now be able to write your own ''' case-statements''' in Ruby. |
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− | | 09 | + | | 09:03 |
|This brings us to the end of this Spoken Tutorial. | |This brings us to the end of this Spoken Tutorial. | ||
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− | | 09 | + | | 09:07 |
− | |Let's summarize. | + | |Let's summarize. In this tutorial, we have learnt to use: |
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− | | 09 | + | | 09:10 |
− | | | + | | '''if''' statement |
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− | | 09 | + | | 09:12 |
− | |''' if | + | | ''' else''' construct, '''if-elsif''' and |
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− | | 09 | + | | 09:15 |
− | |''' | + | | ''' case statements'''. |
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− | | 09 | + | | 09:17 |
− | |''' | + | |As an assignment- write a '''Ruby''' program |
|- | |- | ||
− | | 09 | + | | 09:20 |
− | | | + | |that prompts a user to enter a number, |
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− | | 09 | + | | 09:23 |
− | + | ||
− | + | ||
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− | + | ||
− | + | ||
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|then use the appropriate control-statement | |then use the appropriate control-statement | ||
|- | |- | ||
− | | 09 | + | | 09:26 |
− | |to check if the number is a multiple of 2 | + | |to check if the number is a multiple of 2. |
|- | |- | ||
− | |09 | + | |09:29 |
− | | | + | |If it is, then print: “The number entered is a multiple of 2”. |
|- | |- | ||
− | | 09 | + | | 09:35 |
− | | | + | |If not, it should check- if it is a multiple of 3. |
|- | |- | ||
− | | 09 | + | | 09:38 |
− | | | + | |If it is, then print: “The number entered is a multiple of 3”. |
|- | |- | ||
− | | 09 | + | | 09:43 |
− | | | + | |If not, it should check if it is a multiple of 4. |
|- | |- | ||
− | | 09 | + | | 09:47 |
− | | | + | |If it is, then print: “The number entered is a multiple of 4”. |
|- | |- | ||
− | | 09 | + | | 09:51 |
− | | | + | |If not, it should print: “The number is not a multiple of 2, 3 or 4”. |
|- | |- | ||
− | | 09 | + | | 09:56 |
| Watch the video available at the following link. | | Watch the video available at the following link. | ||
|- | |- | ||
− | | 10 | + | | 10:00 |
− | |It | + | |It summarizes the Spoken Tutorial project. |
|- | |- | ||
− | | 10 | + | | 10:03 |
|If you do not have good bandwidth, you can download and watch it. | |If you do not have good bandwidth, you can download and watch it. | ||
|- | |- | ||
− | | 10 | + | | 10:07 |
− | | | + | | The Spoken Tutorial project team: |
|- | |- | ||
− | | 10 | + | | 10:09 |
− | |Conducts workshops using spoken tutorials | + | | Conducts workshops using spoken tutorials. |
|- | |- | ||
− | |10 | + | |10:13 |
− | |Gives certificates to those who pass an online test | + | | Gives certificates to those who pass an online test. |
|- | |- | ||
− | | 10 | + | | 10:16 |
− | |For more details, please write to contact@spoken-tutorial.org | + | |For more details, please write to: contact@spoken-tutorial.org |
|- | |- | ||
− | | 10 | + | | 10:21 |
− | | | + | | '''Spoken Tutorial''' project is a part of the '''Talk to a Teacher''' project. |
|- | |- | ||
− | | 10 | + | | 10:26 |
|It is supported by the National Mission on Education through ICT, MHRD, Government of India. | |It is supported by the National Mission on Education through ICT, MHRD, Government of India. | ||
|- | |- | ||
− | | 10 | + | | 10:32 |
− | |More information on this | + | |More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro. |
|- | |- | ||
− | | | + | | 10:41 |
− | |This is Anjani Nair signing off. Thanks for watching. | + | |This is Anjani Nair, signing off. Thanks for watching. |
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|} | |} |
Latest revision as of 12:19, 10 March 2017
Time | Narration |
00:01 | Welcome to the spoken tutorial on Control Statements in Ruby. |
00:06 | In this tutorial, we will learn to use: |
00:08 | 'if' statement , 'elsif' statement |
00:11 | 'else, 'case' statements. |
00:14 | Here we are using: Ubuntu version 12.04 |
00:18 | Ruby 1.9.3. |
00:21 | To follow this tutorial, you must have Internet connection. |
00:24 | You must also have knowledge of Linux commands, Terminal and Text-editor. |
00:30 | If not, for relevant tutorials, please visit our website. |
00:34 | Before we begin, recall that we had created “ttt” directory earlier. |
00:38 | Let's go to that directory. |
00:41 | Then to ruby hyphen tutorial control hyphen statements. |
00:47 | Now that we are in that folder, let’s move ahead. |
00:52 | The syntax of the 'if' statement in Ruby is as follows: |
00:56 | if “condition” |
00:58 | ruby code. end |
01:01 | Let us look at an example. |
01:03 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
01:08 | Name it if hyphen statement dot rb. |
01:12 | I have a working example of the if statement. |
01:15 | You can pause the tutorial and type the code as we go through it. |
01:19 | I have declared an if statement in this example. |
01:23 | First, I declare a local variable my_num and assign the value 2345 to it. |
01:31 | Then I declare an if statement. |
01:34 | The puts method declared within the if statement will display the output. |
01:39 | The if statement will check if the value of my_num is greater than 0. |
01:43 | If it is, it will print out the specified string. |
01:47 | Now, let us switch to the terminal and type: |
01:51 | ruby space if hyphen statement dot rb. |
01:57 | The output will display “The value of my_num is greater than 0”. |
02:02 | This output proves that the if condition returned true. |
02:07 | You should now be able to write your own 'if' statement in Ruby. |
02:12 | Let's look at the 'if-else' statement next. |
02:16 | The syntax for using else is: |
02:18 | if “condition” , ruby code |
02:20 | else, ruby code |
02:22 | end |
02:24 | Let us look at an example. |
02:26 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
02:30 | Name it if hyphen else hyphen statement dot rb. |
02:37 | I have a working example of the 'if-else' statement. |
02:40 | You can pause the tutorial and type the code as we go through it. |
02:44 | I have declared an if-else statement in this example. |
02:48 | First I declare a local variable my_num and assign the value of -1 to it. |
02:55 | Then I declare an if statement. |
02:58 | The 'if' statement will check if the value of 'my_num' is greater than 0. |
03:03 | If it is, it will print out the specified string. |
03:06 | If not, it will go to the else statement. |
03:10 | And it will print out the string that is specified there. |
03:13 | Now, let us switch to the terminal and type: |
03:18 | ruby space if hyphen else hyphen statement dot rb |
03:26 | and see the output.The output will display “The value of my_num is lesser than 0”. |
03:32 | This shows that the else statement was executed. |
03:35 | You should now be able to write your own if-else statement in Ruby. |
03:41 | Let's look at the if-elsif statement next. |
03:45 | The syntax for using elsif is: |
03:48 | if “condition” ruby code |
03:50 | elsif “condition” ruby code |
03:52 | else ruby code |
03:54 | end . Let us look at an example. |
03:58 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
04:01 | Name it if hyphen elsif hyphen statement dot rb. |
04:07 | I have a working example of the if-elsif statement. |
04:10 | You can pause the tutorial and type the code as we go through it. |
04:14 | I have declared an if-elsif statement in this example. |
04:19 | Here also, I have declared a local variable my_num and assigned the value -1 to it. |
04:25 | Then I declare an if statement. |
04:28 | The if statement will check if the value of my_num is greater than 0. |
04:32 | If it is, it will print out the specified string. |
04:35 | If this is not true, it will go into the elsif section. |
04:39 | It will now check if the value of my_num is equal to -1. |
04:43 | If it is true, it will print out the string that is specified there. |
04:46 | If the value of my_num is neither greater than 0 nor equal to -1, it will go into the else section. |
04:54 | But, since the value of my_num = -1 it will not proceed to the else block. |
05:00 | And, it will exit the conditional statement. |
05:03 | Now, let us switch to the terminal and type: |
05:07 | ruby space if hyphen elsif hyphen statement dot rb |
05:15 | and see the output. |
05:17 | The output will display “The value of my_num is -1 and is lesser than 0”. |
05:23 | Let's go back to our file and change the value of my_num to 5. |
05:29 | Let's save the code and execute it on the terminal. |
05:35 | So, now it fulfills the if condition and the specified string is printed. |
05:42 | "The value of my_num is greater than 0". |
05:45 | Let's go back to our file and change the value of my_num to -5. |
05:50 | Let's save the code and execute it on the terminal. |
05:55 | In this case, it fulfills the else condition and the puts statement within the else block gets executed. |
06:03 | You should now be able to write your own if-elsif statement in Ruby. |
06:08 | Let us look at the 'case' statement next. |
06:12 | The 'case' statement is a control flow statement based on a particular selection. |
06:17 | Let us look at the syntax of the 'case' statement in order to understand this statement. |
06:22 | The syntax for using case is: |
06:24 | case variable |
06:26 | when “value 1” |
06:28 | ruby code . when “value 2” ruby code |
06:31 | else ruby code . end. |
06:35 | Let us look at an example. |
06:37 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
06:41 | Name it case hyphen statement dot rb. |
06:44 | I have a working example of the 'case' statement. |
06:48 | You can pause the tutorial and type the code as we go through it. |
06:52 | I have declared a case statement in this example. |
06:55 | Here, I have a print statement which will print a question on the terminal. |
07:01 | Then I call a gets which will accept a single line of data from the standard input. |
07:09 | Then I strip the input data of any new line characters using chomp. |
07:15 | I assign the result to a variable named domain. |
07:18 | Then I declare a case statement. |
07:22 | Within that, I declare a when statement . |
07:25 | This checks whether the specified string matches the value of domain. |
07:30 | First, it checks whether the value of domain is “UP”. |
07:34 | If it is so, it will print out “Uttar Pradesh” and exit the case statement. |
07:39 | If domain is not “UP”, it checks whether the value of domain is “MP”. |
07:44 | If it is so, it will print out “Madhya Pradesh” and so on. |
07:48 | It will continue checking the value of domain if no match was found so far. |
07:53 | At this point, it will encounter the else statement |
07:56 | as none of the above conditions were true. |
07:59 | It will subsequently execute the ruby code that follows the else declaration. |
08:03 | It will print “Unknown” as per our example. |
08:07 | Now, save the file. Switch to the terminal and type: |
08:11 | ruby space case hyphen statement dot rb. |
08:18 | “Enter the state you live in:” will be displayed on the terminal. |
08:22 | Type in “UP” and see the output. |
08:25 | The output will display “Uttar Pradesh”. |
08:28 | Next, execute the Ruby file again, like before. |
08:31 | This time, at the prompt, type: “KL” and see the output. |
08:36 | It will print “Kerala”. |
08:38 | Next, execute the file one more time. |
08:41 | This time, at the prompt, type in “TN” and see the output. |
08:47 | It will print “Unknown”. |
08:50 | This is because none of the cases were satisfied. So, the default else statement is executed. |
08:58 | You should now be able to write your own case-statements in Ruby. |
09:03 | This brings us to the end of this Spoken Tutorial. |
09:07 | Let's summarize. In this tutorial, we have learnt to use: |
09:10 | if statement |
09:12 | else construct, if-elsif and |
09:15 | case statements. |
09:17 | As an assignment- write a Ruby program |
09:20 | that prompts a user to enter a number, |
09:23 | then use the appropriate control-statement |
09:26 | to check if the number is a multiple of 2. |
09:29 | If it is, then print: “The number entered is a multiple of 2”. |
09:35 | If not, it should check- if it is a multiple of 3. |
09:38 | If it is, then print: “The number entered is a multiple of 3”. |
09:43 | If not, it should check if it is a multiple of 4. |
09:47 | If it is, then print: “The number entered is a multiple of 4”. |
09:51 | If not, it should print: “The number is not a multiple of 2, 3 or 4”. |
09:56 | Watch the video available at the following link. |
10:00 | It summarizes the Spoken Tutorial project. |
10:03 | If you do not have good bandwidth, you can download and watch it. |
10:07 | The Spoken Tutorial project team: |
10:09 | Conducts workshops using spoken tutorials. |
10:13 | Gives certificates to those who pass an online test. |
10:16 | For more details, please write to: contact@spoken-tutorial.org |
10:21 | Spoken Tutorial project is a part of the Talk to a Teacher project. |
10:26 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
10:32 | More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro. |
10:41 | This is Anjani Nair, signing off. Thanks for watching. |