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

Customization point for providing bounds on a quantity point relative to an origin.

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<xref:mp_units/PointOrigin.adoc[PointOrigin] auto PO>
requires (PO._quantity_spec_.character == quantity_character::real_scalar)
inline constexpr auto quantity_bounds = detail::undefined;
----

== Description

Users specialize this variable template for point origins (both absolute and relative). The value should be an overflow‐policy object that stores the bounds (e.g. `reflect_in_range`, `clamp_to_range`, `wrap_to_range`).

Bounds are always enforced as constraints on `quantity_from(Origin)` — the displacement measured in the frame of the specialized origin. Different origins (including relative ones) may have independent bounds; it is the user's responsibility to keep them consistent when multiple levels of bounds are in use.

Example:

[,cpp]
----
{.cpp}
 // Absolute origin: latitude reflects at poles
 inline constexpr struct equator final : absolute_point_origin<geo_latitude> {} equator;
 template<>
 constexpr auto quantity_bounds<equator> = reflect_in_range{-90 * deg, 90 * deg};

 // Relative origin: AC controller setpoint — comfort range clamped around 21 °C
 inline constexpr struct room_reference_temp final :
     relative_point_origin<point<deg_C>(21)> {} room_reference_temp;
 template<>
 constexpr auto quantity_bounds<room_reference_temp> = clamp_to_range{delta<deg_C>(-3), delta<deg_C>(3)};
----
== Template Parameters

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

| *PO*
| a point origin for which bounds are defined
|===


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