Difference between revisions of "PERL/C2/More-Conditional-statements/English-timed"

|Welcome to the spoken tutorial on ''' if-elsif-else ''' and '''switch''' conditional statements in Perl.

| In this tutorial, we will learn about  

|The ''' if-elsif-else''' statement and ''' switch''' statement in '''Perl '''

| I am using '''Ubuntu Linux12.04''' operating system and '''Perl 5.14.2'''

| You should have basic knowledge of '''Variables '''and''' Comments '''in''' Perl.'''

| ''' if ''' and '''if-else''' statements will be an added advantage.

|Please go through the relevant spoken tutorials on the '''spoken tutorial '''website.

|When all conditions fail then it executes the default '''else''' block  

|The syntax of '''if-elsif-else''' statement is as follows  

|''' if space''' open bracket ''' condition''' close bracket space Open curly bracket press Enter

|piece of code  to be executed when the condition is true semicolon

|Press '''Enter '''

| Close curly bracket space '''elsif''' space open bracket ''' condition''' close bracket space open curly bracket  

|Press '''Enter '''

 

|another piece of code semicolon  

|to be executed when '''elsif condition''' is true  

|Press '''Enter '''

|close curly bracket space ''' else'''  space open curly bracket  

 

| Enter  

|code semicolon  to be executed when both the above conditions are false semicolon

|Press '''Enter '''

| close curly bracket  

| First, the ''' if ''' condition is checked and executed if the condition is true.  

|If not, then the ''' else if''' condition is checked and executed if it is true.  

|Open the Terminal and type  

| and press '''Enter'''

|This will open the ''' conditionalBlocks.pl''' file in '''gedit. '''

| We have assigned the value ''' 'Perl' ''' to variable language.

|Note that, '''eq''' is  '''string comparison''' operator.  

| And then we have the various conditons that we want to check.

|Now, press ctrl+s to save the file.  

| Type, '''perl conditionalBlocks dot pl '''

 

| 03:16

|   03:18

| execution will throw an error and will stop execution of script

| ''' Hi, I am Perl '''

|Assign ''' 'Java' ''' to variable language as shown.  

| 03:37

| Press '''ctrl+s''' to save the file.  

|Type ''' perl conditionalBlocks dot pl '''

 

|   03:53

| The output shown on terminal is ''' Hi, I am Java '''

| Now, let us assign  ''' 'English' ''' to the ''' language''' variable.  

|Type '''perl conditionalBlocks dot pl '''

 

|and press '''Enter.'''

|The output shown on terminal is  

|'''I am not a computer language '''

| The 3 cases imply that;

| Only one ''' if block''' that satisfies the condition will be executed.

| otherwise the default ''' else block''' will get execute.  

|''' “I am a Science graduate” ''' if '''stream''' is ''' science '''

|'''“I am a Commerce graduate” ''' if '''stream''' is '''commerce'''  

|''' “I am an Arts graduate” ''' if ''' stream''' is neither ''' science''' or '''commerce '''

| 05:10

| 05:14

| After that, '''Switch module''' was introduced,

| Note: ''' Modules''' in '''Perl''' will be covered in subsequent tutorials.  

| The syntax of ''' switch''' is as follows:  

| Press '''Enter'''  

| '''switch ''' space open bracket '''dollar value''' close bracket space open curly bracket  

|Press '''Enter '''

|  '''case ''' space 1 space open curly bracket ''' executes when dollar value equal to 1''' close curly bracket.  

| Press '''Enter'''  

|'''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  

| Press ''' Enter '''

 

|''' else''' space open curly bracket ''' executes when dollar value does not match any of the cases '''

|Close curly bracket  

| close curly bracket  

|  Open the Terminal and type  

|and press '''Enter'''

  |Now, type the sample program as shown on the screen.  

| Note: We will learn about '''use keyword''' in detail in subsequent tutorials.  

| Now we'll test the different cases.   

| We have assigned ''' 'Perl' ''' to the variable ''' $var'''

| The value in variable ''' $var''' is checked in the switch statement.  

| In the first case, it matches with the case ''' 'Perl'.'''

| So the code written against this '''case''' will be executed.  

| press '''Enter'''  

|''' I am Perl '''

 

| Now, let us assign ''' 'Linux' ''' to the variable ''' $var '''

|Press ''' Ctrl S''' to save the file.

| Again, the value of variable ''' $var''' will be checked in switch.  

| It matches with the case ''' 'Linux' '''

| So code written against this case will get executed.  

| Now, switch to terminal and execute the script  

| Press '''Enter'''

| The following output is shown on the terminal  

| ''' I am Linux'''

| Switch to ''' sampleSwitch.pl''' in ''' gedit.'''  

| Similarly, if variable ''' $var''' has value ''' 'Java' ''', then second case will be checked.  

| Now, let us assign ''' 'English' ''' to the variable ''' $var'''

| Again, the value of variable ''' $var ''' will be checked in switch.  

| So the ''' else ''' statement will be executed.  

| Now, switch to terminal and execute the script  

| ''' perl sampleSwitch.pl'''

| and Press ''' Enter'''

| The following output is shown on the terminal -

|''' I am not a computer language '''

 

| The 3 cases imply that:  

| The value of the expression decides the ''' case ''' to be executed  

| Only the valid ''' case''' will be executed and  

| When there is no valid '''case''', then the default ''' else ''' case will be executed  

| It is not mandatory to write the '''else case. '''

| In such a scenario,  

| then there will be no output from the ''' switch''' statement.  

| Here is another assignment for you -

| given earlier in this tutorial using ''' switch''' statement.  

| In this tutorial, we have learnt -

| '''switch''' statement in '''Perl '''

 

| '''using sample programs. '''

|Watch the video available at the following link

|It summaries the Spoken Tutorial project

|If you do not have good bandwidth, you can download and watch it

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| Hope you enjoyed this Perl tutorial.  

|This is Amol signing off.