Perl Arithmetic Operators

Perl Operators – Part 2

Perl Course

Foreword: In this part of the series I talk about Arithmetic Operators in Perl.

By: Chrysanthus Date Published: 12 Oct 2015

Introduction

This is part 2 of my series, Perl Operators. In this part of the series I talk about Arithmetic Operators in Perl. In Perl, arithmetic operators are divided into two parts: You have the Additive Operators and the Multiplicative Operators. You should have read the previous part of the series before reaching here, as this is a continuation.

Additive Operators

Addition Operator
Read and try the following code. The explanation is given below:

use strict;

    my $id1 = 20;
    my $id2 = 30;

    my $id3 = $id2 + $id1;
    print $id3;

20 is held in the variable, $id1. 30 is held in the variable, $id2. In the third statement of interest, Perl takes the content of $id2 and adds it to the content of $id1, then it places the result as content for the variable of the newly declared variable, $id3. This addition is done without affecting or changing the contents of $id2 and $id1. The addition is done in a different area of memory.

Subtraction Operator
Read and try the following code. The explanation is given below:

Code example:

use strict;

    my $id1 = 20;
    my $id2 = 30;

    my $id3 = $id2 - $id1;
    print $id3;

20 is held in the variable, $id1. 30 is held in the variable, $id2. In the third statement of interest, Perl takes the content of $id2 and subtracts from it, the content of $id1, then it places the result as content for the variable of the newly declared variable, $id3. This subtraction is done without affecting or changing the contents of $id2 and $id1. The subtraction is done in a different area of memory.

The Negation Operator
The negation operator is the minus sign, it changes a positive number to a negative number. Consider the following statement:

    my $var = -5;

5 is by definition a positive number. The negation operator on the right argument of the ordinary assignment operator, turns the 5 to a negative number. The negative number is stored in $var.

The Dot Operator
The dot (.) is an additive operator, but it is not really used for math (arithmetic); it is used to concatenate strings. Read and try the following program that illustrates this:

use strict;

    my $str1 = "one one";
    my $str2 = " two two";
    my $str3 = " three three";
    my $str = $str1 . $str2 . $str3;

    print $str;

There are three small strings ($str1, $str2, $str3) in the program. They are joined (concatenated) together with the dot operator to form the string, str.

Multiplicative Operators

Multiplication Operator
Read and try the following code. The explanation is given below:

use strict;

    my $id1 = 20;
    my $id2 = 30;

    my $id3 = $id2 * $id1;
    print $id3;

Note that the multiplication operator is * and not X. 20 is held in the variable, $id1. 30 is held in the variable, $id2. In the third statement of interest, Perl takes the content of $id2 and multiplies it with the content of $id1, then it places the result as content for the newly declared variable, $id3. This multiplication is done without affecting or changing the contents of $id2 and $id1. The multiplication is done in a different area of memory.

Division Operator
Read and try the following code. The explanation is given below:
Code example:

use strict;

    my $id1 = 3;
    my $id2 = 15;

    my $id3 = $id2 / $id1;
    print $id3;

Note that the division operator is, / . 3 is held in the variable, $id1. 15 is held in the variable, $id2. In the third statement of interest, Perl takes the content of $id2 and divides it by the content of $id1, then it places the result as content for the newly declared variable, $id3. This multiplication is done without affecting or changing the contents of $id2 and $id1. The multiplication is done in a different area of memory.

Division Operator
Read and try the following code. The explanation is given below:
Code example:

use strict;

    my $id1 = 3;
    my $id2 = 15;

    my $id3 = $id2 / $id1;
    print $id3;

Note that the division operator is, / . 3 is held in the variable, $id1. 15 is held in the variable, $id2. In the third statement of interest, Perl takes the content of $id2 and divides it by the content of $id1, then it places the result as content for the newly declared variable, $id3. This multiplication is done without affecting or changing the contents of $id2 and $id1. The multiplication is done in a different area of memory.

Modulus Operator
The modulus operator divides the first argument by the second argument and returns the remainder. Read and try the following code:

use strict;

    my $id1 = 17;
    my $id2 = 12;

    my $id3 = $id1 % $id2;

        print $id3;

The Modulus operator is the percentage sign. For the third statement of interest, Perl takes the content of $id1 and divides it by the content of $id2. The remainder of the division is placed in the variable, $id3. The division is done in a different area of memory.

The Repetition Operator
The repetition operator is x. It takes two arguments: one on the left and one on the right. The one on the right is a number. The argument on the left can be a character, string or list.

The operator repeats (printing) what is on the left the number of times of the number on the right. The operator can work with the print statement to send the repetition to the browser or console.

Read and try the following program:

use strict;

    print '-' x 80, "\n"; # prints row of dashes
    print "\t" x 3, "text text", "\n" ; #prints 3 tabs and then "text text" on same line

The printed tabs (\t) effects will not appear at the browser but will appear at the console.

Read and try the following program for a list of strings:

use strict;

    my @arr = ("one ", "two ", "three ") x 4;
    print @arr;

The list is in parentheses. There are three items in the list. The repetition is in groups of the three items. The array ends up with 12 items.

Exponentiation
The exponentiation operator is not really an arithmetic operator. I have just included it in this tutorial for convenience. The operator is **. It is used to type exponentials: something like “4 raised to the power 2” is written as 4**2. The result of 4**2 is 16, that is, 4 X 4 = 16. Read and try the following code:

use strict;

    my $result = 4**2;
    print $result;

Apart from the negation and exponentiation operator, each arithmetic operator operates from left to right; that is from the left argument to the right argument. The negation and exponentiation operators operate in the opposite direction. The negation operator is a unary operator.

Left Associativity
If you have consecutive arithmetic operators, the one on the left will be evaluated first, followed by the one next to it coming to the right, followed by the one next to it, rightward, and so on. Consider the following code:

use strict;

    my $ret = 9 - 5 - 2;

    print $ret;

The output is:

2

The output is 2 because 9-5 is evaluated first before the result of 4 is used to evaluate 4-2. If 5-2 had been evaluated first, before 9-3, the output would have been 6.

The exponentiation operator is right associative, while the arithmetic operators are left associative.

That is it for arithmetic operators. We take a break here and continue in the next part of the series.

Chrys

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