//
// Copyright (c) 2023 Alan de Freitas (alandefreitas@gmail.com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/boostorg/url
//


= Formatting

Algorithms to format URLs construct a mutable URL by parsing and applying arguments to a URL template.
The following example uses the cpp:format[]
function to construct an absolute URL:


[source,cpp]
----
include::example$unit/snippets.cpp[tag=snippet_format_1,indent=0]
----

The rules for a format URL string are the same as for a cpp:std::format_string[], where replacement fields are delimited by curly braces.
The URL type is inferred from the format string.

The URL components to which replacement fields belong are identified before replacement is applied and any invalid characters for that formatted argument are percent-escaped:


[source,cpp]
----
include::example$unit/snippets.cpp[tag=snippet_format_2,indent=0]
----

Delimiters in the URL template, such as cpp:":"[], cpp:"//"[], cpp:"?"[], and cpp:"#"[], unambiguously associate each replacement field to a URL component.
All other characters are normalized to ensure the URL is valid:


[source,cpp]
----
include::example$unit/snippets.cpp[tag=snippet_format_3a,indent=0]
----



[source,cpp]
----
include::example$unit/snippets.cpp[tag=snippet_format_3b,indent=0]
----

The function cpp:format_to[] can be used to format URLs into any modifiable URL container.


[source,cpp]
----
include::example$unit/snippets.cpp[tag=snippet_format_4,indent=0]
----

As with cpp:std::format[], positional and named arguments are supported.


[source,cpp]
----
include::example$unit/snippets.cpp[tag=snippet_format_5a,indent=0]
----

The cpp:arg[] function can be used to associate names with arguments:


[source,cpp]
----
include::example$unit/snippets.cpp[tag=snippet_format_5b,indent=0]
----

A second overload based on cpp:std::initializer_list[]
is provided for both cpp:format[] and cpp:format_to[].
These overloads can help with lists of named arguments:


[source,cpp]
----
include::example$unit/snippets.cpp[tag=snippet_format_5c,indent=0]
----

