anchor.diff:  
   (define type-callback 61)
   (define type-float* (vm:or type-float #x40))
  +(define NewtonWorld* type-vptr)
  +(define dFloat* (vm:or type-float #x40))
   
   (define NewtonWorldGetVersion (dlsym $ type-fix+ "NewtonWorldGetVersion"))
   (define NewtonWorldFloatSize  (dlsym $ type-fix+ "NewtonWorldFloatSize"))
  
positive.code:    (glEnd)
     (glPopMatrix))
  
  
  
  (gl:run
  
     "7. Newton"
  
  ; init
  (lambda ()
  
negative.code: (NewtonDestroyCollision collision)
  
  
  ; ...
  (define ApplyGravity (cons
     (list type-vptr type-void* type-int+)
     (lambda (body timestep threadIndex)
  