= _of_(S.v[2])
 b = _f_(S.[3])

 u =  + b
 ffc =  - b
 uc =  * b
  =   b
  = (, b)

J.(" + b = " ++ _f_(u))
J.(" - b = " ++ _f_(ffc))
J.(" * b = " ++ _f_(uc))
J.("  b = " ++ _f_())
J.(" % b = " ++ _f_())