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PlayBASIC Tutorial:  From Variables To Arrays (Intro To Arrays) 2017-09-17


Welcome programmers,  in this tutorial we're going to introduce the concept of arrays starting out from variables.  So first we build a simple game  loop that controls two characters using only variables.  The characters are represented on screen as filled circles.  After we get up to speed with the variable version we then move onto how we can use parallel integer arrays to store the various properties of the characters.  The array version can control as many or as few characters as you like, which is the benefit of Arrays over Variables


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Video:






Example #1 - Variables Example

[pbcode]

 
  Xpos1  = 400
  Ypos1  = 300
     
  Xpos2  = 100
  Ypos2  = 100

     
  setfps 20  
     
 do    

   cls rgb(10,20,40)

   ; Draw circle 1        
    Circle Xpos1,Ypos1, 32, true
 
    Xpos1 = Xpos1 + 2
    Ypos1 = Ypos1 - 4
 
     Xpos1 = WrapValue(Xpos1,0,800)     
      Ypos1 = WrapValue(Ypos1,0,600)     
 
 

   ; Draw circle 2      
    Circle Xpos2,Ypos2, 64, true
 
    Xpos2 = Xpos2 + 2
    Ypos2 = Ypos2 + 2
      Xpos2 = WrapValue(Xpos2,0,800)     
      Ypos2 = WrapValue(Ypos2,0,600)     
 
    sync
 loop
 

[/pbcode]




Example #2 - Arrays Example - Using Parallel Arrays To Store Character Properties

[pbcode]

Setfps 20

  Number_Of_Characters = 50

  dim Xpos( Number_Of_Characters  )
  dim Ypos( Number_Of_Characters  )
  dim size( Number_Of_Characters  )
  dim Xspeed( Number_Of_Characters )
  dim Yspeed( Number_Of_Characters )
  dim Colour( Number_Of_Characters )
 
 
  for lp = 1 to Number_Of_Characters
        Xpos(lp)  = rnd(800)
        Ypos(lp)  = rnd(600)
        Size(lp)  = rndrange(16,50)
        Xspeed(lp) = rndrange(-5, 5)
      Yspeed(lp) = rndrange(-5,5)
      Colour(lp) = rndrgb()
  next
 
 
 do
    
       Cls rgb(0,400,20)
      
       for lp=1 to Number_Of_Characters
          
          Radius = Size(lp)

          circlec xpos(lp),ypos(lp),Radius,true,Colour(lp)
          
        //  xpos(lp) = Xpos(lp) + Xspeed(lp)
        //  ypos(lp) = ypos(lp) + Yspeed(lp)
          
          xpos(lp) = wrapvalue(xpos(lp) + Xspeed(lp) , -Radius, 800 + Radius)
          ypos(lp) = wrapvalue(ypos(lp) + Yspeed(lp) , -Radius, 600 + Radius)
                     
       next
         
       Sync
    loop
[/pbcode]