let cvt_binop = function
    PbinTimes -> CTTbinTimes
  | PbinDiv -> CTTbinDiv 
  | PbinPlus | PbinMinus -> assert false
  | PbinModulo -> CTTbinModulo
  | PbinLshift -> CTTbinLshift
  | PbinRshift -> CTTbinRshift
  | PbinLogAnd -> CTTbinLogAnd
  | PbinLogOr -> CTTbinLogOr
  | PbinIntAnd -> CTTbinIntAnd
  | PbinIntOr -> CTTbinIntOr
  | PbinIntXor -> CTTbinIntXor
  | PbinLessThan -> CTTbinLessThan
  | PbinLessEqual -> CTTbinLessEqual
  | PbinGtrThan -> CTTbinGtrThan
  | PbinGtrEqual -> CTTbinGtrEqual
  | PbinEqual -> CTTbinEqual
  | PbinNotEqual -> CTTbinNotEqual