:relfileprefix: ../../../ [#boost-urls-url-2constructor-0f0] == xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::xref:boost/urls/url.adoc[pass:[url]]::url Constructor === Synopsis Declared in header `` [source,cpp,subs="verbatim,macros,-callouts"] ---- url() noexcept; ---- === Description Default constructed urls contain a zero-length string. This matches the grammar for a relative-ref with an empty path and no query or fragment. [,cpp] ---- url u; ---- [,cpp] ---- this->empty() == true ---- === Constant. === Throws nothing. [,cpp] ---- relative-ref = relative-part [ "?" query ] [ "#" fragment ] ---- === 4.2. Relative Reference (rfc3986)