anchor.diff:          (basis-r20 basis) 0.0
           (basis-r21 basis) 0.0))
   
  -(defconstant +basis-sin-precision+ 0.999999999) ;; 1.0-1.0e-9
  +(define-constant +basis-sin-precision+ 0.999999999) ;; 1.0-1.0e-9
   
   ;;      _                                _
   ;;     |  c2c3  s1s2c3-c1s3  s1s3+c1s2c3  |  s1,c1 : roll
  
positive.code:   (r02 0.0) (r12 0.0) (r22 1.0) (z2 0.0)
    (tx 0.0) (ty 0.0) (tz 0.0) (one 1.0))
  
  (defconstant +matrix-identity+
    #(1.0 0.0 0.0 0.0
      0.0 1.0 0.0 0.0
      0.0 0.0 1.0 0.0
  
negative.code:       :positive
        :negative))
  
  (define-constant +epsilon+ 0.0000001)
  
  (defun roughly-equal (number-1 number-2)
    (< (abs (- number-1 number-2)) +epsilon+))
  