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

Resolves a dynamic (`{}`‐style) spec against the format arguments.

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class Handler,
    typename Context>
constexpr
void
handle_dynamic_spec(
    int& value,
    xref:mp_units/utility/fmt_arg_ref.adoc[fmt_arg_ref<Context::char_type>] ref,
    Context& ctx);
----

== Description

If `ref` does not reference an argument (`kind == fmt_arg_id_kind::none`), `value` is left unchanged.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *value*
| the spec value to update when `ref` references an argument
| *ref*
| the reference to the format argument holding the dynamic value, if any
| *ctx*
| the format context providing access to the format arguments
|===


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