[#mp_units-utility-parse_dynamic_spec]
= xref:mp_units.adoc[mp_units]::xref:mp_units/utility.adoc[utility]::parse_dynamic_spec
:relfileprefix: ../../
:mrdocs:

Parses a spec value that may be a literal integer or a `{}`‐style dynamic argument reference.

== Synopsis

Declared in `<mp‐units/utility/format.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    std::forward_iterator It,
    typename Char = std::iter_value_t<It>>
[[nodiscard]]
constexpr
It
parse_dynamic_spec(
    It begin,
    It end,
    int& value,
    xref:mp_units/utility/fmt_arg_ref.adoc[fmt_arg_ref<Char>]& ref,
    std::basic_format_parse_context<Char>& ctx);
----

== Return Value

an iterator past the parsed spec value, or `begin` when neither form is present

[NOTE]
====
The return value https://en.cppreference.com/cpp/language/attributes/nodiscard[should not be discarded^].
====
== Parameters

[cols="1,4"]
|===
| Name| Description
| *begin*
| the beginning of the range to parse; must be non‐empty
| *end*
| the end of the range to parse
| *value*
| updated with the parsed value when it is a literal integer
| *ref*
| updated with the referenced argument when the value is `{}`‐style dynamic
| *ctx*
| the format parse context, used to validate a dynamic argument reference
|===


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