In order to write this game we need to learn about two simple, and unrelated topics: How to generate random numbers in Perl and How to get the integer part of a number.

Integer part of a fractional number

The int() function returns the integer part of its parameter:

use strict;
use warnings;
use 5.010;

my $x = int 3.14;
say $x;          # will print 3

my $z = int 3;
say $z;          # will also print 3.

                 # Even this will print 3.
my $w = int 3.99999;
say $w;

say int -3.14;   # will print -3

Random numbers

A call to the rand($n) function of Perl will return a random fractional number between 0 and $n. It can be 0 but not $n.

If $n = 42 then a call to the rand($n) will return a random number between 0 and 42. It can be 0 but not 42. For example it can be 11.264624821095826 .

If we don't give any value then rand() will default to give values between 0 and 1 including 0 but excluding 1.

Combining rand with int allows us to generate random whole numbers.

use strict;
use warnings;
use 5.010;

my $z = int rand 6;
say $z;

Will return a number between 0 and 6. It can be 0 but cannot be 6. So it can be any of the following numbers: 0,1,2,3,4,5.

If we now add 1 to the result then we get any of the numbers 1,2,3,4,5,6 which is the same as throwing a dice.

Exercise: Number Guessing game

This is the beginning of a game we are going to write. A small but fun game.

Write a script in which using the rand() function the computer "thinks" about a whole number between 1 and 200. The user has to guess the number.

After the user types in his guess the computer tells if this was bigger or smaller than the number it generated.

At this point there is no need to allow the user to guess several times. We will get there in a later episode. Of course I won't stop you from reading about the while loop in Perl, you can read that and let the user guess several times.