free_formula (QuantOp on ot f) = QuantOp on' ot' f'
     where on' = mkFreeName on
           ot' = free_op_type ot
           f' = free_formula f
free_formula (QuantOp on ot f) = QuantOp on' ot' f'
     where on' = mkFreeName on
           ot' = free_op_type ot
           f' = free_formula f
free_formula (QuantOp on ot f) = QuantOp on' ot' f'
     where on' = mkFreeName on
           ot' = free_op_type ot
           f' = free_formula f