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

• Perl functions
• functions with arguments
• function with return values

• Ubuntu Linux12.04 operating system
• Perl 5.14.2
• and the gedit Text Editor

You can use any text editor of your choice.

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

# piece of code

}

• The definition of a declared function is written between curly braces.
• This function does not take any arguments.
• And, it does not return anything.

• 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;

Here is my simpleFunction dot pl file in gedit.

#!/usr/bin/perl

# Call the function

printText();

sub printText {

print “This is illustration of simple Perl Function\n”;

}

<<pause>>

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.

perl simpleFunction.pl

perl simpleFunction dot pl

and press Enter.

This is illustration of simple Perl Function

($variable1, $variable2,...$variableN) = @_;

# Action to be perform on the arguments pass to this function

}

Here is my functionWithArgs script in gedit.

#!/usr/bin/perl

# Call the function

addVariables(10, 20);

sub addVariables {

($var1, $var2) = @_;

$addition = $var1 + $var2;

print “Addition is: $addition\n”;

}

<<pause>>

Here, we are calling a function with two 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.

• @_ is a special Perl array.
• This array is used to store the passed arguments.
• Similarly, we can catch the passed arguments in variables as

$var1 = shift @_;

$var2 = shift @_;

• shift @_ removes the element at first position from @_ array
• and assigns it to a variable
• Another way is;
  $var1 = $_[0];
  $var2 = $_[1];
• The above mentioned way is similar to fetching elements of @_ array using index.

Addition is: 30

by typing -

perl functionWithArgs dot pl

and press Enter

The output is as displayed on the terminal.

<pause>>

#piece of code

return $variable;

}

#!/usr/bin/perl

# Call the function

$addition = addVariables(10, 20);

print “Addition is: $addition\n”;

sub addVariables {

($var1, $var2) = @_;

$add = $var1 + $var2;

return $add;

}

<<pause>>

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.

perl funcWithSingleRtrnVal.pl

Addition is: 30

So, switch to terminal and type-

perl funcWithSingleRtrnVal dot pl

and press Enter.

The output is as displayed on the terminal.

<pause>>

#piece of code

return ($variable1, $variable2,...$variableN);

}

#!/usr/bin/perl

use Data::Dumper;

# Call the function

($var1, $var2, $addition) = addVariables(10, 20);

print "Addition of $var1 and $var2 is: $addition\n";

sub addVariables {

($var1, $var2) = @_;

$add = $var1 + $var2;

return ($var1, $var2, $add);

}

@marksArray = getMarksArray();

print "Array\n";

print Dumper \@marksArray;

%marksHash = getMarksHash();

print "Hash\n";

print Dumper \%marksHash;

sub getMarksArray {

@mArray = (98, 96, 95);

return @mArray;

}

sub getMarksHash {

%mHash = (

'English' => 98,

'Physics' => 96,

'Chemistry' => 95

);

return %mHash;

}

<<pause>>

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

The return values of the function are caught in variables $var1, $var2, $addition.

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

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

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

Addition of 10 and 20 is: 30

Array

$VAR1 = [

98,

96,

95

];

Hash

$VAR1 = {

'Chemistry' => 95,

'English' => 98,

'Physics' => 96

};

perl funcWithMultipleRtrnVals dot pl

and press Enter.

The output is as displayed on the terminal.

<pause>>

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(@arrayName);

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

And observe their outputs.

In this tutorial, we have learnt -

• Functions in Perl
• functions with arguments and
• functions which return values

using sample programs.

1. Write a function which takes 3 arguments.
2. Perform some action on these arguments
3. Return the result of the action performed on the arguments and print the same.

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