Difference between revisions of "PERL/C2/More-Conditional-statements/English-timed"
From Script | Spoken-Tutorial
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|piece of code to be executed when the condition is true semicolon | |piece of code to be executed when the condition is true semicolon | ||
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|close curly bracket space ''' else''' space open curly bracket | |close curly bracket space ''' else''' space open curly bracket | ||
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| '''gedit conditionalBlocks dot pl space ampersand''' | | '''gedit conditionalBlocks dot pl space ampersand''' | ||
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|02:26 | |02:26 | ||
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| Type, '''perl conditionalBlocks dot pl ''' | | Type, '''perl conditionalBlocks dot pl ''' | ||
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| execution will throw an error and will stop execution of script | | execution will throw an error and will stop execution of script | ||
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| 03:23 | | 03:23 | ||
| Now press '''Enter.''' | | Now press '''Enter.''' | ||
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|Switch to the terminal and execute the file. | |Switch to the terminal and execute the file. | ||
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|03:43 | |03:43 | ||
|Type ''' perl conditionalBlocks dot pl ''' | |Type ''' perl conditionalBlocks dot pl ''' | ||
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| Press ''' ctrl+s ''' to save the file. | | Press ''' ctrl+s ''' to save the file. | ||
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|04:09 | |04:09 | ||
|Switch to the terminal and execute the file. | |Switch to the terminal and execute the file. | ||
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|04:13 | |04:13 | ||
|Type '''perl conditionalBlocks dot pl ''' | |Type '''perl conditionalBlocks dot pl ''' | ||
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|''' “I am an Arts graduate” ''' if ''' stream''' is neither ''' science''' or '''commerce ''' | |''' “I am an Arts graduate” ''' if ''' stream''' is neither ''' science''' or '''commerce ''' | ||
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|05:06 | |05:06 | ||
|Now let us learn about the '''switch''' statement. | |Now let us learn about the '''switch''' statement. | ||
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| Press ''' Enter ''' | | Press ''' Enter ''' | ||
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|Press '''Enter ''' | |Press '''Enter ''' | ||
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|06:38 | |06:38 | ||
− | + | |Now, type the sample program as shown on the screen. | |
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|''' I am Perl ''' | |''' I am Perl ''' | ||
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|09:12 | |09:12 | ||
|''' I am not a computer language ''' | |''' I am not a computer language ''' | ||
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Revision as of 10:51, 10 July 2014
Time | Narration |
00:00 | Welcome to the spoken tutorial on if-elsif-else and switch conditional statements in Perl. |
00:07 | In this tutorial, we will learn about |
00:10 | The if-elsif-else statement and switch statement in Perl |
00:15 | I am using Ubuntu Linux12.04 operating system and Perl 5.14.2 |
00:22 | I will also be using the gedit Text Editor. |
00:25 | You can use any text editor of your choice. |
00:29 | You should have basic knowledge of Variables and Comments in Perl. |
00:34 | and knowledge of for, foreach, while and do-while loops and |
00:38 | if and if-else statements will be an added advantage. |
00:43 | Please go through the relevant spoken tutorials on the spoken tutorial website. |
00:48 | If-elsif-else statement in Perl can be used |
00:52 | to test multiple conditions and |
00:54 | When all conditions fail then it executes the default else block |
00:59 | The syntax of if-elsif-else statement is as follows |
01:04 | if space open bracket condition close bracket space Open curly bracket press Enter |
01:13 | piece of code to be executed when the condition is true semicolon |
01:18 | Press Enter |
01:20 | Close curly bracket space elsif space open bracket condition close bracket space open curly bracket |
01:30 | Press Enter |
01:31 | another piece of code semicolon |
01:33 | to be executed when elsif condition is true |
01:37 | Press Enter |
01:39 | close curly bracket space else space open curly bracket |
01:44 | Enter |
01:45 | code semicolon to be executed when both the above conditions are false semicolon |
01:51 | Press Enter |
01:52 | close curly bracket |
01:55 | First, the if condition is checked and executed if the condition is true. |
02:01 | If not, then the else if condition is checked and executed if it is true. |
02:06 | Otherwise, the code within else block is executed. |
02:11 | Now let us look at an example of if-elsif-else statement. |
02:16 | Open the Terminal and type |
02:19 | gedit conditionalBlocks dot pl space ampersand |
02:26 | and press Enter |
02:28 | This will open the conditionalBlocks.pl file in gedit. |
02:33 | Type the following piece of code as displayed on the screen. |
02:38 | We have assigned the value 'Perl' to variable language. |
02:44 | Note that, eq is string comparison operator. |
02:49 | And then we have the various conditons that we want to check. |
02:55 | Now, press ctrl+s to save the file.
|
02:58 | Then switch to terminal and execute file directly. |
03:02 | Type, perl conditionalBlocks dot pl |
03:09 | Note: I am skipping the compilation step. It is not a mandatory step for executing Perl scripts. |
03:16 | If there is any compilation error, |
03:18 | execution will throw an error and will stop execution of script |
03:23 | Now press Enter. |
03:25 | The output shown on the terminal is |
03:27 | Hi, I am Perl |
03:29 | Now, let us look at our next case. |
03:31 | Switch to gedit. |
03:33 | Assign 'Java' to variable language as shown. |
03:37 | Press ctrl+s to save the file. |
03:40 | Switch to the terminal and execute the file. |
03:43 | Type perl conditionalBlocks dot pl |
03:50 | and press Enter. |
03:53 | The output shown on terminal is Hi, I am Java |
03:59 | Again let us switch back to gedit. |
04:03 | Now, let us assign 'English' to the language variable. |
04:07 | Press ctrl+s to save the file. |
04:09 | Switch to the terminal and execute the file. |
04:13 | Type perl conditionalBlocks dot pl |
04:18 | and press Enter. |
04:19 | The output shown on terminal is |
04:22 | I am not a computer language |
04:27 | The 3 cases imply that; |
04:29 | Only one if block that satisfies the condition will be executed. |
04:35 | otherwise the default else block will get execute. |
04:39 | We can have multiple elsif conditions as per our requirement, like this. |
04:46 | Here is an assignment for you - |
04:48 | Write an if-elsif-else statement to print |
04:51 | “I am a Science graduate” if stream is science |
04:55 | “I am a Commerce graduate” if stream is commerce
|
04:59 | “I am an Arts graduate” if stream is neither science or commerce |
05:06 | Now let us learn about the switch statement. |
05:10 | Till Perl 5.8, there was no switch statement in Perl. |
05:14 | After that, Switch module was introduced, |
05:18 | which provided the functionality of switch statement. |
05:22 | Note: Modules in Perl will be covered in subsequent tutorials. |
05:27 | The syntax of switch is as follows: |
05:30 | use Switch semicolon |
05:32 | Press Enter |
05:34 | switch space open bracket dollar value close bracket space open curly bracket |
05:42 | Press Enter |
05:44 | case space 1 space open curly bracket executes when dollar value equal to 1 close curly bracket. |
05:53 | Press Enter |
05:55 | case space single quote a single quote space open curly bracket executes when dollar value equal to single quote a single quote close curly bracket |
06:09 | Press Enter |
06:10 | else space open curly bracket executes when dollar value does not match any of the cases |
06:18 | Close curly bracket |
06:19 | Press Enter |
06:20 | close curly bracket |
06:22 | Let us understand switch using a sample program. |
06:26 | Open the Terminal and type |
06:29 | gedit sampleSwitch dot pl space ampersand |
06:36 | and press Enter |
06:38 | Now, type the sample program as shown on the screen. |
06:43 | Let us understand how the switch statement works. |
06:46 | The use Switch statement includes the Switch module inside the Perl code. |
06:54 | Note: We will learn about use keyword in detail in subsequent tutorials. |
07:00 | Now we'll test the different cases. |
07:03 | We have assigned 'Perl' to the variable $var |
07:08 | The value in variable $var is checked in the switch statement. |
07:14 | In the first case, it matches with the case 'Perl'. |
07:19 | So the code written against this case will be executed. |
07:24 | Press ctrl+s to save the file. |
07:27 | Now, switch to terminal and execute the script |
07:31 | perl sampleSwitch.pl |
07:36 | press Enter |
07:38 | The following output is shown on the terminal |
07:41 | I am Perl |
07:43 | Switch back to sampleSwitch.pl in gedit. |
07:48 | Now, let us assign 'Linux' to the variable $var |
07:52 | Press Ctrl S to save the file. |
07:57 | Again, the value of variable $var will be checked in switch. |
08:03 | It matches with the case 'Linux' |
08:05 | So code written against this case will get executed. |
08:10 | Now, switch to terminal and execute the script |
08:15 | perl sampleSwitch.pl |
08:19 | Press Enter |
08:21 | The following output is shown on the terminal |
08:24 | I am Linux |
08:26 | Switch to sampleSwitch.pl in gedit. |
08:30 | Similarly, if variable $var has value 'Java' , then second case will be checked. |
08:38 | Now, let us assign 'English' to the variable $var |
08:42 | Again, the value of variable $var will be checked in switch. |
08:47 | It does not match any of the case statements. |
08:50 | So the else statement will be executed. |
08:54 | Now, switch to terminal and execute the script |
09:00 | perl sampleSwitch.pl |
09:07 | and Press Enter |
09:09 | The following output is shown on the terminal - |
09:12 | I am not a computer language |
09:17 | The 3 cases imply that: |
09:20 | The value of the expression decides the case to be executed |
09:25 | Only the valid case will be executed and |
09:28 | When there is no valid case, then the default else case will be executed |
09:35 | It is not mandatory to write the else case. |
09:39 | In such a scenario, |
09:41 | if none of the cases match |
09:44 | then there will be no output from the switch statement. |
09:48 | Here is another assignment for you - |
09:50 | Re-write the previous assignment |
09:53 | given earlier in this tutorial using switch statement. |
09:57 | Let us summarize. |
09:59 | In this tutorial, we have learnt - |
10:01 | if-elsif-else statement and |
10:04 | switch statement in Perl |
10:05 | using sample programs. |
10:08 | Watch the video available at the following link
|
10:12 | It summaries the Spoken Tutorial project |
10:15 | If you do not have good bandwidth, you can download and watch it |
10:20 | The Spoken Tutorial Project Team Conducts workshops using spoken tutorials |
10:25 | Gives certificates to those who pass an online test |
10:30 | For more details, please write to contact at spoken hyphen tutorial dot org |
10:36 | Spoken Tutorial Project is a part of the Talk to a Teacher project |
10:40 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
10:47 | More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro |
10:58 | Hope you enjoyed this Perl tutorial. |
11:00 | This is Amol signing off. |
11:03 | Thanks for joining. |