[#boost-urls-url-2constructor]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/url.adoc[url]::url
:relfileprefix: ../../../
:mrdocs:


Constructor

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/url.hpp#L120[boost/url/url.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/url/2constructor-0f0.adoc[url]() noexcept;
----

[.small]#xref:boost/urls/url/2constructor-0f0.adoc[_» more..._]#

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
explicit
xref:boost/urls/url/2constructor-002.adoc[url](core::string_view s);
----

[.small]#xref:boost/urls/url/2constructor-002.adoc[_» more..._]#

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/url/2constructor-01.adoc[url](xref:boost/urls/url.adoc[url]&& u) noexcept;
----

[.small]#xref:boost/urls/url/2constructor-01.adoc[_» more..._]#

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
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xref:boost/urls/url/2constructor-001.adoc[url](xref:boost/urls/url_view_base.adoc[url_view_base] const& u);
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[.small]#xref:boost/urls/url/2constructor-001.adoc[_» more..._]#

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
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xref:boost/urls/url/2constructor-0f7.adoc[url](xref:boost/urls/url.adoc[url] const& u);
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[.small]#xref:boost/urls/url/2constructor-0f7.adoc[_» more..._]#

== 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.


=== Example

[,cpp]
----
url u;
----

=== Postconditions

[,cpp]
----
this->empty() == true
----

=== Complexity

Constant.


=== Exception Safety

Throws nothing.


=== BNF

[,cpp]
----
relative-ref  = relative-part [ "?" query ] [ "#" fragment ]
----

=== Specification

link:https://datatracker.ietf.org/doc/html/rfc3986#section-4.2[4.2. Relative Reference (rfc3986)]



== Exceptions


|===
| Name | Thrown on

| `system_error`
| The input does not contain a valid url.


| `std::length_error`
| `u.size() > max_size()`.


|===

== Parameters


|===
| Name | Description

| *s*
| The string to parse.


| *u*
| The url to move from.


|===



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