Perl 101 (Part 2) - Of Variables And Operators - 2 2 ... (Page 3 of 8 )
As you've already seen in last time's lesson, Perl comes with all the standard arithmetic operators - addition [+], subtraction [-], division [/] and multiplication [*] - and quite a few non-standard ones. Here's an example which demonstrates the important ones:
#!/usr/bin/perl
# get a number
print "Gimme a number! ";
$alpha = <STDIN>;
# get another number
print "Gimme another number! ";
$beta = <STDIN>;
# process input
chomp($alpha);
chomp($beta);
# standard stuff
$sum = $alpha + $beta;
$difference = $alpha - $beta;
$product = $alpha * $beta;
$quotient = $alpha / $beta;
# non-standard stuff
$remainder = $alpha % $beta;
$exponent = $alpha ** $beta;
# display the result
print "Sum: $sum\n";
print "Difference: $difference\n";
print "Product: $product\n";
print "Quotient from division: $quotient\n";
print "Remainder from division: $remainder\n";
print "Exponent: $exponent\n";
As with all other programming languages, division and
multiplication take precedence over addition and subtraction, although parentheses can be used to give a particular operation greater precedence. For example,
#!/usr/bin/perl
print(10 + 2 * 4);
returns 18, while
#!/usr/bin/perl
print((10 + 2) * 4);
returns 48.
In addition to these operators, Perl also
comes with the very useful auto-increment [++] and auto-decrement [--] operators, which you'll see a lot of in the next lesson. For the moment, all you need to know is that the auto-increment operator increments the value of the variable to which it is applied by 1, while the auto-decrement operator does exactly the same thing, but in the opposite direction. Here's an example:
#!/usr/bin/perl
# initial value
$a = 7;
print("Initial value: ", $a, "\n");
# increment and display
$a++;
print("After increment: ", $a, "\n");
