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

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

| In this tutorial, we will learn about -

|''' Perl functions '''

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

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

|For this tutorial, I am using  

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

| ''' gedit''' Text Editor  

|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.   

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

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

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

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

|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.'''

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

| ''' use ModuleFileName semicolon '''

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

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

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

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

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

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

|''' perl simpleFunction dot pl'''

|The output will be as shown on the terminal

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

| 02:48

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

|   02:57

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

| 03:02

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

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

|@_ 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.  

| 03:42

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

|This ''' array''' is used to store the passed '''arguments'''.   

| 03:51

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

|   03:56

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

| 04:04

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

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

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

|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'''

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

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

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

|The output is as displayed on the screen

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

|Let us understand the same using a sample program.  

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

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

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

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

|Save the file.  

|Now let us execute the script.  

| 06:20

|So, switch to terminal and type-

| 06:24

| The output is as displayed on the terminal.  

| 06:43

| 06:48

| 06:53

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

| 07:04

|Please do like wise in your text editor

| 07:08

| 07:21

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

| 07:31

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

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

| Save your file.  

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

| 08:10

| 08:20

| 08:32

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

| 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.  

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

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

|In this tutorial, we have learnt -

|''' Functions in Perl'''  

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

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

|Here is assignment for you -

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

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

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

|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

|  The Spoken Tutorial Project Team  Conducts workshops using spoken tutorials

|Gives certificates to those who pass an online test

|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

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

| Hope you enjoyed this Perl tutorial.  

|This is Amol signing off.