Actionscript Cookbook

5.9. Simulating Dice

Problem

You want to mimic rolling dice.

Solution

Use the randRange( ) method to generate random numbers in the desired range.

Discussion

You can use the randRange( ) method from Recipe 5.7 to generate random integer values to simulate rolling a die or dice in your Flash movies. Mimicking the rolling of dice is an important feature in many games you might create using ActionScript, and the randRange( ) method makes your job easy.

// Include Math.as to have access to Math.randRange(  ).
#include "Math.as"

// Calling Math.randRange(  ) with min = 1 and max = 6 generates 
// a random number as though you are rolling a six-sided die.
die1 = Math.randRange(1, 6);

// Add the results of two "rolls" together to simulate a pair of six-sided dice.
dice = Math.randRange(1, 6) + Math.randRange(1, 6);

Warning

Math.randRange(1, 12) does not correctly simulate a pair of six-sided dice because the results must be between 2 and 12, not 1 and 12. Does Math.randRange(2, 12) give the correct result? No, it does not! Math.randRange(2, 12) results in a smooth distribution of numbers from 2 to 12, whereas in games played with two dice, 7 is much more common than 2 or 12. Therefore, you must simulate each die separately and then add the results together. Furthermore, in many games, such as backgammon, game play depends on the individual value of each die, not simply the total of both dice, so you’ll want to keep these results separate.

It is not uncommon to want to generate a random number ...