[#BloombergLP-bslfmt-basic_format_parse_context-next_arg_id]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslfmt.adoc[bslfmt]::xref:BloombergLP/bslfmt/basic_format_parse_context.adoc[basic&lowbar;format&lowbar;parse&lowbar;context]::next&lowbar;arg&lowbar;id
:relfileprefix: ../../../
:mrdocs:

Return the index of the next unused argument&period;

== Synopsis

Declared in `&lt;bslfmt&lowbar;formatparsecontext&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
constexpr
size&lowbar;t
next&lowbar;arg&lowbar;id();
----

== Description

If the indexing mode is unset, the indexing mode is set to `e&lowbar;AUTOMATIC`&period; If the indexing mode is `e&lowbar;MANUAL`, caused by a previous call to `check&lowbar;arg&lowbar;id` then an exception of type `format&lowbar;error` is thrown&period; If there are no remaining unused arguments then an exception of type `format&lowbar;error` is thrown&period;

== Return Value

the index of the next unused argument


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