Small Basic - Random Numbers

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Random numbers can be very useful in your Small Basic games.  They can be used to make the game play vary from one game to the next.

The Small Basic keyword to get a random number is Math.GetRandomNumber(maxNumber) .  It will return a random integer between 1 and the input value maxNumber.

Here are a few ideas and tips:

Random Position and Speed

We can position sprites with random positions and velocities.

radius `` = ``25

numSprite `` = ``10

gw `` = ``GraphicsWindow``.``Width

gh `` = ``GraphicsWindow``.``Height

For `` i `` = `` 1 `` To ``numSprite

  ``sprite``[``i`` ] `` = ``Shapes``.``AddEllipse``(``2``*``radius``,``2``*``radius``)

  ``spritePosX``[``i`` ] `` = ``radius``+``Math``.``GetRandomNumber``(``gw``-``2``*``radius``)

  ``spritePosY``[``i`` ] `` = ``radius``+``Math``.``GetRandomNumber``(``gh``-``2``*``radius``)

  ``spriteVelX``[``i`` ] `` = ``Math``.``GetRandomNumber``(``11``)``-``6

  ``spriteVelY``[``i`` ] `` = ``Math``.``GetRandomNumber``(``11``)``-``6

EndFor

 

While ``"True"

  `` For `` i `` = `` 1 `` To ``numSprite

    ``spritePosX``[``i`` ] `` = ``spritePosX``[``i``]``+``spriteVelX``[``i``]

    ``spritePosY``[``i`` ] `` = ``spritePosY``[``i``]``+``spriteVelY``[``i``]

    `` If ``(``spritePosX``[``i`` ] `` < ``radius`` ) ``Then

      ``spritePosX``[``i`` ] `` = ``radius

      ``spriteVelX``[``i`` ] `` = ``-``spriteVelX``[``i``]

    `` ElseIf ``(``spritePosX``[``i`` ] `` > ``gw``-``radius`` ) ``Then

      ``spritePosX``[``i`` ] `` = ``gw``-``radius

      ``spriteVelX``[``i`` ] `` = ``-``spriteVelX``[``i``]

    ``EndIf

    `` If ``(``spritePosY``[``i`` ] `` < ``radius`` ) ``Then

      ``spritePosY``[``i`` ] `` = ``radius

      ``spriteVelY``[``i`` ] `` = ``-``spriteVelY``[``i``]

    `` ElseIf ``(``spritePosY``[``i`` ] `` > ``gh``-``radius`` ) ``Then

      ``spritePosY``[``i`` ] `` = ``gh``-``radius

      ``spriteVelY``[``i`` ] `` = ``-``spriteVelY``[``i``]

    ``EndIf

    ``Shapes``.``Move``(``sprite``[``i``]``,``spritePosX``[``i``]``-``radius``,``spritePosY``[``i``]``-``radius``)

  ``EndFor

  ``Program``.``Delay``(``20``)

EndWhile

Random Branching

We can randomly do different things in the code,  perhaps equivalent to rolling a dice.

dice `` = ``Math``.``GetRandomNumber``(``6``)

If ``(`` dice `` = ``1`` ) ``Then

  ``TextWindow``.``WriteLine``(``"Do something for a dice roll of 1"``)

ElseIf ``(`` dice `` = ``2`` ) ``Then

  ``TextWindow``.``WriteLine``(``"Do something for a dice roll of 2"``)

ElseIf ``(`` dice `` = ``3`` ) ``Then

  ``TextWindow``.``WriteLine``(``"Do something for a dice roll of 3"``)

ElseIf ``(`` dice `` = ``4`` ) ``Then

  ``TextWindow``.``WriteLine``(``"Do something for a dice roll of 4"``)

ElseIf ``(`` dice `` = ``5`` ) ``Then

  ``TextWindow``.``WriteLine``(``"Do something for a dice roll of 5"``)

ElseIf ``(`` dice `` = ``6`` ) ``Then

  ``TextWindow``.``WriteLine``(``"Do something for a dice roll of 6"``)

EndIf

We could also only do something with a probability, say 1 in 10.

If ``(``Math``.``GetRandomNumber``(``10`` ) `` = ``1`` ) ``Then

  ``TextWindow``.``WriteLine``(``"This is a 1 in 10 event!!!"``)

Else

  ``TextWindow``.``WriteLine``(``"A 10% probability event didn't happen"``)

EndIf

Ranges and Intervals

If we want random numbers over a different range (not 1 to maxNumber) or with smaller intervals, for example 0.2, then we can use the following formula.

rand `` = `` min `` + ``(``Math``.``GetRandomNumber``(``1``+``(``max``-``min``)``/``interval``)``-``1``)``*``interval

Here is an example using this to create random numbers between -5 and 3, with intervals of 0.2.

min `` = ``-``5

max `` = ``3

interval `` = ``0.2

For `` i `` = `` 1 `` To ``1000

  ``Random``(``)

  ``TextWindow``.``WriteLine``(``rand``)

EndFor

Sub ``Random

  `` rand `` = `` min `` + ``(``Math``.``GetRandomNumber``(``1``+``(``max``-``min``)``/``interval``)``-``1``)``*``interval

EndSub