Difference between revisions of "PERL/C2/Arrays/English"

• Index of an array
• Length of an array
• Accessing elements of an array
• Looping over an array
• Sequential Array
• Array Slicing

I will also be using the gedit Text Editor.

You can use any text editor of your choice.

Knowledge of Comments, loops and conditional statements will be an added advantage.

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

• Array index starts from zero always.
• In Perl, it is not necessary to declare the length of an array.
• Array length expands/shrinks as and when elements are added/removed from it.

@myArray = (1, 2, 3, 'abc', 10.3);

$#myArray

gedit arrayIndex.pl & >> Enter

gedit arrayIndex dot pl space ampersand

and press Enter.

This will open arrayIndex dot pl file in geditor.

#!/usr/bin/perl

@myArray = (1, 2, 3, 'abc', 10.3);

print “Last index of myArray is: $#myArray\n”;

<<pause>>

$#myArray

As array index starts from zero, the last index value will be 4

i.e number of elements, which is 5, minus 1.

Type

perl arrayIndex.pl

perl arrayIndex dot pl

and press Enter.

Last index of myArray is: 4

Last index of myArray is: 4

These are as follows-

1. Index of an array + 1; $#array + 1
2. Using PERL inbuilt scalar function; scalar(@array)
3. Assign array to a scalar variable; $arrayLength = @array

gedit arrayLength.pl & >> Enter

Switch to the terminal and type -

gedit arrayLength dot pl space ampersand

Press Enter.

This will open arrayLength Perl script in gedit.

#!/usr/bin/perl

@myArray = (1, 2, 3, 'abc', 10.3);

$length = @myArray;

print "Length of an array using index: ", $#myArray + 1, "\n";

print "Length of an array using scalar variable: $length\n";

print "Length of an array using scalar function: ", scalar(@myArray), "\n";

<<pause>>

Here we have declared & defined an array which contains 5 elements.

So, output will display 5.

Highlighted here are various ways to find the length of an array in Perl.

We have concatenated the output in the print statement using comma.

Switch to terminal and type-

perl arrayLength dot pl and press Enter.

Length of an array using scalar variable: 5

Length of an array using scalar function: 5

1. First Position
2. Last Position
3. Any position

gedit perlArray dot pl space ampersand

and press Enter.

This will open perlArray dot pl script in gedit.

#!/usr/bin/perl

@myArray = (1, 2, 3, 'abc', 10.3);

# Access the first element of an array

print "First element of myArray is: ", $myArray[0], "\n";

# Access 3rd element of an array

print "3rd Element of myArray is: ", $myArray[2], "\n";

# Access last element of an array

print "Last element of myArray is: ", $myArray[$#myArray], "\n";

<<pause>>

$myArray[0]

print "First element of myArray is: ", $myArray[0], "\n";

print "Last element of myArray is: ", $myArray[$#myArray], "\n";

1. myArray is declared with @ (at the rate) sign.
2. But, to access an array element we need to use $ (dollar) sign.
3. To access the element at 3rd position, we need to pass index as 2

i.e position of element minus 1.

Here, to access the first element of myArray

zero is passed as index.

To access the last element of myArray we have passed the last index to myArray.

Recall, we had learnt about this earlier.

perl perlArray.pl

perl perlArray dot pl

and press Enter.

1. Using for loop
2. Using foreach loop

gedit loopingOverArray dot pl space ampersand

Press Enter

#!/usr/bin/perl

@myArray = (1, 2, 3);

# Iterate over an array using for loop

for ($i = 0; $i <= $#myArray; $i++) {

# Do the operation on individual element

print "Printing element using for loop: ", $myArray[$i], "\n";

}

# Used to separate the output on terminal

print "============================================\n";

# Iterate over an array using foreach loop

foreach $element (@myArray) {

# Do the operation on individual element

print "Printing element using foreach loop: $element\n";

}

Type the piece of code as shown on the screen

<<pause>>

Here, we are printing each element of the array by iterating the index.

The for loop will execute till the value of i variable reaches the last index of the array.

Here, foreach loop will be executed for each element of the array.

Once the array reaches its last element, it will exit the foreach loop.

• If you are not aware of for and foreach loops,
• please go through the relevant tutorials
• on the spoken tutorial website.

perl scalars.pl

perl loopingOverArray dot pl

and press Enter.

Printing element using for loop: 1

Printing element using for loop: 2

Printing element using for loop: 3

==============================

Printing element using foreach loop: 1

Printing element using foreach loop: 2

Printing element using foreach loop: 3

<< Will just highlight the output and will not read it while recording >>

• @alphaArray = (a..d);
• i.e alphaArray will contain elements 'a', 'b', 'c' and 'd'
• Similarly
• @numericArray = (1..5); is same as @numericArray = (1, 2, ,3, 4, 5);

This is nothing but extracting part of an array and dumping it into a new array.

@array = (19, 23, 56, 45, 87, 89);

@newArray = @myarray[1, 4];

After slicing, newArray will look like this -

@newArray = (23, 87);

In this tutorial, we have learnt to-

• Find index of an array
• Find length of an array
• Access elements of an array
• Loop over an array
• Sequenial Array
• Array Slicing

using sample programs.

1. Declare an array of rainbow colors
2. Print 4th element of this array
3. Print Length and last index of this array
4. Loop over each element of the array using for & foreach loops
5. Declare array as
   @myArray = (1..9); and then
   Create an array of odd numbers from above array using array slicing.

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