namespace boost { namespace text { template<utf16_iter I, std::sentinel_for< I > S = I> struct utf16_view; template<utf32_iter I, std::sentinel_for< I > S = I> struct utf32_view; template<utf8_iter I, std::sentinel_for< I > S = I> struct utf8_view; namespace v1 { } } }namespace std { namespace ranges { } }