[#mp_units-constraint_violation_handler-0c]
= xref:mp_units.adoc[mp_units]::constraint_violation_handler
:relfileprefix: ../
:mrdocs:

Customization point for handling domain constraint violations.

== Synopsis

Declared in `<mp‐units/framework/customization_points.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<typename Rep>
struct constraint_violation_handler;
----

== Description

The library calls `constraint_violation_handler<Rep>::on_violation(msg)` when a domain constraint is violated (e.g., out‐of‐bounds value, non‐negativity).

No default implementation is provided. When no specialization exists for a given Rep, the library uses MP_UNITS_EXPECTS directly (which may compile to nothing in release builds). Specializing this trait opts the type into guaranteed enforcement.

== Template Parameters

[cols="1,4"]
|===
|Name|Description

| *Rep*
| the representation type
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#