'   RC Constrained Random Points on a Circle

nomainwin

WindowWidth  =400
WindowHeight =430

open "Constrained Random Points on a Circle" for graphics_nsb as #w

#w "trapclose [quit]"
#w "down ; size 7 ; color red ; fill black"

for i =1 to 1000
  do
     x =int( 30 *rnd( 1)) -15
     y =int( 30 *rnd( 1)) -15
  loop until IsInRange( x, y) =1
  #w "set "; 200 +10 *x; " "; 200 - 10 *y
next

wait

function IsInRange( x, y)
  z =sqr( x*x +y*y)
  if 10 <=z and z <=15 then IsInRange =1 else IsInRange =0
end function

[quit]
close #w
end