namespace boost {
  namespace text {
    struct text_sort_key;
    int compare(text_sort_key const &, text_sort_key const &);
    namespace v1 {
      template<code_point_iter I, std::sentinel_for< I > S> 
        text_sort_key 
        collation_sort_key(I, S, collation_table const &, 
                           collation_strength = collation_strength::tertiary, 
                           case_first = case_first::off, 
                           case_level = case_level::off, 
                           variable_weighting = variable_weighting::non_ignorable, 
                           l2_weight_order = l2_weight_order::forward);
      template<code_point_iter I, std::sentinel_for< I > S> 
        text_sort_key 
        collation_sort_key(I, S, collation_table const &, 
                           collation_flags = collation_flags::none);
      template<code_point_range R> 
        text_sort_key 
        collation_sort_key(R &&, collation_table const &, 
                           collation_flags = collation_flags::none);
      template<code_point_iter I1, std::sentinel_for< I1 > S1, 
               code_point_iter I2, std::sentinel_for< I2 > S2> 
        int collate(I1, S1, I2, S2, collation_table const &, 
                    collation_strength = collation_strength::tertiary, 
                    case_first = case_first::off, 
                    case_level = case_level::off, 
                    variable_weighting = variable_weighting::non_ignorable, 
                    l2_weight_order = l2_weight_order::forward);
      template<code_point_iter I1, std::sentinel_for< I1 > S1, 
               code_point_iter I2, std::sentinel_for< I2 > S2> 
        int collate(I1, S1, I2, S2, collation_table const &, 
                    collation_flags = collation_flags::none);
      template<code_point_range R1, code_point_range R2> 
        int collate(R1 const &, R2 const &, collation_table const &, 
                    collation_flags = collation_flags::none);
    }
  }
}