====== Examples ======

These are sample pieces of XC=BASIC source code.

===== Example 1: Fibonacci series =====

  rem ** fibonacci series **
  
  max = 32767
  t1 = 0
  t2 = 1
  
  print "fibonacci series:"
  loop:
    print t1, " "
    nx = t1 + t2
    t1 = t2
    t2 = nx
    if nx < max then goto loop
  end

===== Example 2: Kaleidoscope effect =====

Submitted by Eugenio Rapella. Note that it is valid to use line numbers instead of labels in **XC=BASIC**.

  1 const D12=12
  2 const D55=55296
  3 const D40=40
  4 const D23=23
  
  10 poke 53280,0:poke 53281,0
  20 for t=0 to 999
  30 poke 1024+t,81 : rem pallino
  40 poke 55296+t,0 : rem nero
  50 next t
  60 let x!=cast!(D12*rnd%())
  65 let y!=cast!(D12*rnd%())
  67 let c!=rshift!(rnd!(),4)
  
  70 m1 = D40 * y! : m2 = D40 * x!
  75 n1 = D23 - x! : n2 = D23 - y!
  
  90 poke D55+x!+m1,c!
  95 poke D55+y!+m2,c!
  100 poke D55+n1+m1,c!
  105 poke D55+n2+m2,c!
  110 poke D55+x!+D40*n2,c!
  115 poke D55+y!+D40*n1,c!
  120 poke D55+n1+D40*n2,c!
  125 poke D55+n2+D40*n1,c!
  130 goto 60


===== Example 3: Bouncing ball =====

  rem ** bouncing ball **
  
  const SCREEN = 1024
  const RASTER = 53266
  const BALL = 81
  const SPACE = 32
  
  x = 1
  y = 1
  dx = 1
  dy = 1
  i = 0
  
  gosub cls
  
  loop:
    charat x, y, BALL
    gosub wait_frame
    charat x, y, SPACE
  
    if x = 0 then dx = 1
    if x = 39 then dx = -1
    if y = 0 then dy = 1
    if y = 24 then dy = -1
  
    x = x + dx
    y = y + dy
  
    goto loop
  
  cls:
    poke SCREEN + i,SPACE
    inc i
    if i < 1000 then goto cls
    return
  
  wait_frame:
    if peek(RASTER) < 250 then goto wait_frame
    return
    
===== Example 4: USR() function =====

This example implements the << (left shift) operation on an integer for demonstration purposes.

  rem -- example implementation of the << (left shift)
  rem -- operation using an USR function
  
  print usr(@fn_leftShift, 896)
  end
  
  rem -- Function fn_leftShift(int argument)
  rem --
  
  fn_leftShift:
  asm "
      ; The argument is available on the stack
      tsx
      asl $0102,x
      rol $0101,x
  
      ; Note this is the only valid way to return from an user function
      ; The caller will pull back the result from the stack
      jmp ($02fe)
    "