Using 1D arrays as a 2D array

[kevin]

  Using 1D arrays as a 2D array

   This example uses a fixed size 1d array within a type and addresses it as if it were a 2D array, which is represented on screen as a grid pattern.  To do this we declare the array field as being Width*Height cells.  To address the correct cell, we're multiplying the Y coordinate by the array width and adding the X coordinate.    

   To simplified the set/getting of values from our emulated 2d array, I've wrapped some function that will read fvalues from and write values to the array, with bound clipping.

PlayBASIC Code: [Select]

;   Addressing a 1D array as if was a 2D array
   
   Constant GridWidth =10
   Constant GridHeight =20

   Type tGrid

         ; Screen position
         Xpos,Ypos

         ; Movement Speed along X axis
         SpeedX

         ; Movement Speed along Y axis
         SpeedY

         // width* height ofthe grid cells on screen
         BlockWidth
         BlockHeight
         
         // COlour of the grid
         Colour

         // our 2d array declared as a 1D array
         GridArray(GridWidth*GridHeight)   
   EndType

   ; declare a list of grids
   Dim Grid as tGrid list


   ; ruin through and add/initialize them randomly   
   For lp=1 to 10

         ; alloc and add new item to the Grid List
         Grid = New tGrid

         ; declare a pointer of tGrid Type,   
         Dim Me as tGrid pointer 

         ; Get a pointer to the current list item
         ; and store it in ME.  SO now ME is pointing at
         ; this item inside the list.  
         me=GetListPtr(Grid())

         ; Init the fields with some random values
         me.Xpos=rnd(800)
         me.ypos=rnd(600)
         me.speedx=rnd(2)
         me.speedy=rnd(2)
         me.Colour=rndrgb()

         me.BlockWidth =rndrange(1,3)*16
         me.BlockHeight=rndrange(1,3)*16

         ; Init the 2d array within this field
         for ylp=0 to GridHeight-1
            for xlp=0 to GridWidth-1
               ; Call the SetGrid function to store
               ; this value at this X/Y coordinate within
               ; the 
               SetGrid(Me, Xlp,ylp,rnd(100))
            next         
         next

   next


   Setfps 60

   Do
      Cls
      // draw them 
      For Each Grid()
            Me=GetListPtr(Grid())
            Me.xpos+=Me.SpeedX
            if Me.xpos>800 then Me.xpos=-800
            Me.ypos+=Me.SpeedY
            if Me.ypos>600 then Me.ypos=-600

            DrawGrid(Me)
      next         

      Sync
   loop
   


psub DrawGrid(Me as tGrid pointer)
   if int(me)

      Ypos=Me.Ypos
      BlockWidth   =me.blockWidth
      BlockHeight   =me.blockHeight

      for ylp=0 to GridHeight-1
         Xpos=Me.Xpos
         
         Ypos2=Ypos+BlockHeight
         for xlp=0 to GridWidth-1
            // Call the get grid function to get
            // this item from the array
            Level=GetGrid(Me, Xlp,ylp)

            // Use this value as the fade level of the grid colour
            ThisRgb=rgbFade(Me.Colour,Level)

            // draw a blox to represent this cell on screen
            Boxc Xpos,Ypos,Xpos+BlockWidth,Ypos2,true,ThisRGB

                        
            Xpos+=BlockWidth                     
         next         

         Ypos+=BlockHeight
      next




   endif
EndPsub



Psub SetGrid(Me as tGrid pointer, Xpos,Ypos,Value)
   ; Perform some safety checks on the cordinates, so we can't
   ; read/write outside of the array data block
   if Xpos>-1 and Xpos<GridWidth
      if Ypos>-1 and Ypos<GridHeight
         Ypos*=GridWidth
         me.GridArray(Ypos+Xpos) = Value
      endif
   endif
endPsub

Psub GetGrid(Me as tGrid pointer, Xpos,Ypos)
   ; Some safety check on the cordinates
   if Xpos>-1 and Xpos<GridWidth
      if Ypos>-1 and Ypos<GridHeight
         Ypos*=GridWidth
         Value=me.GridArray(Ypos+Xpos)
      endif
   endif
endPsub Value