Difference between revisions of "PERL/C2/Functions-in-Perl/English-timed"

{| border=1

{| border=1

   

   

|-

|-

|Welcome to the spoken tutorial on ''' Functions in Perl'''.

|Welcome to the spoken tutorial on ''' Functions in Perl'''.

|-

|-

| In this tutorial, we will learn about -  

| In this tutorial, we will learn about -  

|-

|-

|''' Perl functions '''

|''' Perl functions '''

   

   

|-

|-

| ''' functions''' with '''arguments '''

| ''' functions''' with '''arguments '''

   

   

|-

|-

|''' function''' with '''return values'''  

|''' function''' with '''return values'''  

|-

|-

|For this tutorial, I am using  

|For this tutorial, I am using  

   

   

|-

|-

| ''' Ubuntu Linux12.04''' operating system  

| ''' Ubuntu Linux12.04''' operating system  

|-

|-

|''' Perl 5.14.2''' and  

|''' Perl 5.14.2''' and  

|-

|-

| ''' gedit''' Text Editor  

| ''' gedit''' Text Editor  

|-

|-

|You can use any text editor of your choice.  

|You can use any text editor of your choice.  

   

   

|-

|-

|You should have basic knowledge of ''' variables, comments, loops, conditional statements''' and ''' Data Structures''' in '''Perl.'''

|You should have basic knowledge of ''' variables, comments, loops, conditional statements''' and ''' Data Structures''' in '''Perl.'''

   

   

|-

|-

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

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

   

   

|-

|-

|We will first see some simple ''' Perl functions.'''

|We will first see some simple ''' Perl functions.'''

|-

|-

|In ''' Perl, functions''', also called as ''' subroutines''', are declared with ''' sub keyword.'''

|In ''' Perl, functions''', also called as ''' subroutines''', are declared with ''' sub keyword.'''

|-

|-

| The definition of a declared ''' function''' is written between curly braces.  

| The definition of a declared ''' function''' is written between curly braces.  

|-

|-

|This ''' function''' does not take any ''' arguments.'''  

|This ''' function''' does not take any ''' arguments.'''  

|-

|-

| And, it does not return anything.  

| And, it does not return anything.  

   

   

|-

|-

|Note: ''' function''' definition can be written anywhere in the script or in another '''module'''.  

|Note: ''' function''' definition can be written anywhere in the script or in another '''module'''.  

|-

|-

|This ''' module''', must then be included in the script, to use this ''' function.'''  

|This ''' module''', must then be included in the script, to use this ''' function.'''  

   

   

|-

|-

|To include the ''' module ''' file in the script, one has to use the following syntax-  

|To include the ''' module ''' file in the script, one has to use the following syntax-  

|-

|-

| ''' use ModuleFileName semicolon '''

| ''' use ModuleFileName semicolon '''

   

   

|-

|-

|Let us understand this using a sample program.  

|Let us understand this using a sample program.  

|-

|-

|Open a file in your text editor and name it as ''' simpleFunction dot pl'''

|Open a file in your text editor and name it as ''' simpleFunction dot pl'''

   

   

|-

|-

| Here is my ''' simpleFunction dot pl'''  file in '''gedit.'''  

| Here is my ''' simpleFunction dot pl'''  file in '''gedit.'''  

|-

|-

| Type the code as displayed on the screen.  

| Type the code as displayed on the screen.  

   

   

|-

|-

|Here, we are just calling a ''' function''', which we have defined.  

|Here, we are just calling a ''' function''', which we have defined.  

|-

|-

|Then, the execution control is passed to that ''' function.'''  

|Then, the execution control is passed to that ''' function.'''  

   

   

|-

|-

|This is the declaration & definition of the ''' function.'''  

|This is the declaration & definition of the ''' function.'''  

   

   

|-

|-

|This ''' function''' will print out the given text.  

|This ''' function''' will print out the given text.  

|-

|-

|Save your file.  

|Save your file.  

|-

|-

|Then switch to the terminal and execute the ''' Perl script''' by typing  

|Then switch to the terminal and execute the ''' Perl script''' by typing  

|-

|-

|''' perl simpleFunction dot pl'''

|''' perl simpleFunction dot pl'''

|-

|-

|and press '''Enter.'''

|and press '''Enter.'''

   

   

|-

|-

|The output will be as shown on the terminal

|The output will be as shown on the terminal

|-

|-

|Now, let us see a ''' function''' with '''arguments.'''

|Now, let us see a ''' function''' with '''arguments.'''

   

   

|-

|-

|Let us understand this function using a sample program.  

|Let us understand this function using a sample program.  

   

   

|-

|-

| Open a file in your text editor and name it as '''functionWithArgs dot pl'''

| Open a file in your text editor and name it as '''functionWithArgs dot pl'''

   

   

|-

|-

|Here is my ''' functionWithArgs''' script in '''gedit. '''

|Here is my ''' functionWithArgs''' script in '''gedit. '''

|-

|-

| Type the following piece of code as shown on the screen.  

| Type the following piece of code as shown on the screen.  

   

   

|-

|-

|Here, we are calling a function with ''' arguments, 10'''  and '''20'''.  

|Here, we are calling a function with ''' arguments, 10'''  and '''20'''.  

   

   

|-

|-

| The passed '''arguments''' are caught in ''' $var1''' & ''' $var2.'''  

| The passed '''arguments''' are caught in ''' $var1''' & ''' $var2.'''  

   

   

|-

|-

|@_ is a special '''Perl variable.''' We will cover its details in future tutorials.  

|@_ is a special '''Perl variable.''' We will cover its details in future tutorials.  

|-

|-

|This '''function''' performs the addition of 2 '''variables''' and prints the answer.  

|This '''function''' performs the addition of 2 '''variables''' and prints the answer.  

   

   

|-

|-

|Save your file.  

|Save your file.  

|-

|-

| ''' @_ '''is a special Perl array.  

| ''' @_ '''is a special Perl array.  

   

   

|-

|-

   

   

|-

|-

| Similarly, we can catch the passed ''' arguments''' in ''' variables''' as  

| Similarly, we can catch the passed ''' arguments''' in ''' variables''' as  

|-

|-

|  ''' $var1 space = space  shift @_  semicolon'''

|  ''' $var1 space = space  shift @_  semicolon'''

   

   

|-

|-

|''' $var2 space  = space  shift @_  semicolon'''

|''' $var2 space  = space  shift @_  semicolon'''

|-

|-

| '''shift @_ removes the element at first position from @_ array '''

| '''shift @_ removes the element at first position from @_ array '''

|-

|-

| and assigns it to a ''' variable '''

| and assigns it to a ''' variable '''

|-

|-

|Another way is; ''' $var1 space  =  space dollar underscrore open square bracket zero close square bracket semicolon '''

|Another way is; ''' $var1 space  =  space dollar underscrore open square bracket zero close square bracket semicolon '''

|-

|-

| ''' $var2 space  =  space dollar underscrore open square bracket 1 close square bracket semicolon'''

| ''' $var2 space  =  space dollar underscrore open square bracket 1 close square bracket semicolon'''

   

   

|-

|-

|The above mentioned way is similar to fetching ''' elements''' of '''@_ array''' using '''index.'''

|The above mentioned way is similar to fetching ''' elements''' of '''@_ array''' using '''index.'''

|-

|-

|Now, switch to terminal and execute the script by typing -  

|Now, switch to terminal and execute the script by typing -  

|-

|-

|''' perl functionWithArgs dot pl''' and press '''Enter '''

|''' perl functionWithArgs dot pl''' and press '''Enter '''

|-

|-

|The output is as displayed on the screen

|The output is as displayed on the screen

   

   

|-

|-

| Now, let us look at a '''functions''' which returns a single value.  

| Now, let us look at a '''functions''' which returns a single value.  

|-

|-

|Let us understand the same using a sample program.  

|Let us understand the same using a sample program.  

|-

|-

|Let me switch to ''' funcWithSingleRtrnVal dot pl ''' script in '''gedit.'''

|Let me switch to ''' funcWithSingleRtrnVal dot pl ''' script in '''gedit.'''

   

   

|-

|-

|Open a file in your text editor and type the following piece of code as shown.

|Open a file in your text editor and type the following piece of code as shown.

   

   

|-

|-

|Here, we are calling ''' addVariables function''' with '''parameters''' 10 and 20.  

|Here, we are calling ''' addVariables function''' with '''parameters''' 10 and 20.  

   

   

|-

|-

|The return value of the ''' function''' is caught in ''' $addition variable.'''

|The return value of the ''' function''' is caught in ''' $addition variable.'''

|-

|-

|This function does the addition of the passed parameters and returns the answer.  

|This function does the addition of the passed parameters and returns the answer.  

|-

|-

|Save the file.  

|Save the file.  

   

   

|-

|-

|Now let us execute the script.  

|Now let us execute the script.  

|-

|-

|So, switch to terminal and type-  

|So, switch to terminal and type-  

|-

|-

|''' perl funcWithSingleRtrnVal dot pl'''  and press '''Enter.'''  

|''' perl funcWithSingleRtrnVal dot pl'''  and press '''Enter.'''  

|-

|-

| The output is as displayed on the terminal.  

| The output is as displayed on the terminal.  

   

   

|-

|-

| Now, let us see a function which returns multiple values.  

| Now, let us see a function which returns multiple values.  

   

   

|-

|-

| Let us understand the same, using a sample program.  

| Let us understand the same, using a sample program.  

|-

|-

| In gedit, I have opened a file and named it as ''' funcWithMultipleRtrnVals dot pl'''  

| In gedit, I have opened a file and named it as ''' funcWithMultipleRtrnVals dot pl'''  

|-

|-

|Please do like wise in your text editor

|Please do like wise in your text editor

|-

|-

| Now, type the following piece of code as shown.  

| Now, type the following piece of code as shown.  

|-

|-

|Here, we are calling '''addVariables''' function with parameters 10 and 20.

|Here, we are calling '''addVariables''' function with parameters 10 and 20.

   

   

|-

|-

| The return values of the function are caught in variables ''' $var1, $var2 and  $addition'''  

| The return values of the function are caught in variables ''' $var1, $var2 and  $addition'''  

   

   

|-

|-

| This function does the addition and returns the passed parameters and the resultant answer.  

| This function does the addition and returns the passed parameters and the resultant answer.  

|-

|-

|This illustration demonstrates how we can return an ''' array'''  from a '''function'''.

|This illustration demonstrates how we can return an ''' array'''  from a '''function'''.

|Similarly, this demonstrates how ''' hash''' can be returned from a function.  

|Similarly, this demonstrates how ''' hash''' can be returned from a function.  

|-

|-

| Save your file.  

| Save your file.  

|-

|-

| Now let us execute the ''' Perl''' script on the terminal by typing -  

| Now let us execute the ''' Perl''' script on the terminal by typing -  

   

   

|-

|-

| '''perl funcWithMultipleRtrnVals dot pl '''

| '''perl funcWithMultipleRtrnVals dot pl '''

|-

|-

| and press '''Enter.'''

| and press '''Enter.'''

|-

|-

| The output is as displayed on the terminal.

| The output is as displayed on the terminal.

|-

|-

|'''Perl'''  provides several '''inbuilt functions.'''

|'''Perl'''  provides several '''inbuilt functions.'''

|-

|-

| We learnt some of them in earlier tutorials. For eg- ''' Arrays, Hash, sort, scalar, each, keys''' etc.  

| We learnt some of them in earlier tutorials. For eg- ''' Arrays, Hash, sort, scalar, each, keys''' etc.  

   

   

|-

|-

|Calling '''inbuilt functions''', similar to calling any other function, which we define.  

|Calling '''inbuilt functions''', similar to calling any other function, which we define.  

|-

|-

|E.g ''' sort open bracket @arrayName close bracket semicolon'''

|E.g ''' sort open bracket @arrayName close bracket semicolon'''

 

 

|-

|-

| Try incorporating some ''' inbuilt functions''' in the sample programs we used.  

| Try incorporating some ''' inbuilt functions''' in the sample programs we used.  

|-

|-

|And observe their outputs.  

|And observe their outputs.  

|-

|-

| Let us summarize.  

| Let us summarize.  

|-

|-

|In this tutorial, we have learnt -  

|In this tutorial, we have learnt -  

   

   

|-

|-

|''' Functions in Perl'''  

|''' Functions in Perl'''  

|-

|-

| ''' functions''' with '''arguments''' and   

| ''' functions''' with '''arguments''' and   

|-

|-

|''' functions''' which '''return values''' using sample programs.  

|''' functions''' which '''return values''' using sample programs.  

|-

|-

|Here is assignment for you -  

|Here is assignment for you -  

|-

|-

|Write a '''function''' which takes 3 '''arguments. '''

|Write a '''function''' which takes 3 '''arguments. '''

|-

|-

|Perform some action on these '''arguments '''

|Perform some action on these '''arguments '''

|-

|-

|Return the result of the action performed on the '''arguments''' and print the same.  

|Return the result of the action performed on the '''arguments''' and print the same.  

|-

|-

|Watch the video available at the following link

|Watch the video available at the following link

|-

|-

|It summaries the Spoken Tutorial project

|It summaries the Spoken Tutorial project

   

   

|-

|-

|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

   

   

|-

|-

|  The Spoken Tutorial Project Team  Conducts workshops using spoken tutorials

|  The Spoken Tutorial Project Team  Conducts workshops using spoken tutorials

   

   

|-

|-

|Gives certificates to those who pass an online  test

|Gives certificates to those who pass an online  test

   

   

|-

|-

|For more details, please write to contact at spoken hyphen tutorial dot org

|For more details, please write to contact at spoken hyphen tutorial dot org

   

   

|-

|-

|  Spoken Tutorial Project is a part of the Talk to a  Teacher project

|  Spoken Tutorial Project is a part of the Talk to a  Teacher project

   

   

|-

|-

|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.

   

   

|-

|-

|More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro

|More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro

   

   

|-

|-

|  Hope you enjoyed this Perl tutorial.  

|  Hope you enjoyed this Perl tutorial.  

   

   

|-

|-

|This is Amol signing off.

|This is Amol signing off.

   

   

|-

|-

|Thanks for joining.

|Thanks for joining.

   

   

|}

|}