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

Scale `value` by the unit magnitude passed as `m,` converting to type `To.`

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename To,
    xref:mp_units/UnitMagnitude.adoc[UnitMagnitude] M,
    typename From>
requires detail::MagnitudeScalable<From>
[[nodiscard]]
constexpr
auto
scale(
    M m,
    From const& value);
----

== Description

When `From` provides a magnitude‐aware `operator*(From,M)` customization point, it is used first. The return type may differ from `To` (e.g. a representation with scaled bounds). Otherwise, the built‐in floating‐point or integer path is used and the result type is `To.`

Use this in custom `operator*(T, UnitMagnitude)` implementations to reuse the library's built‐in scaling logic instead of duplicating it.


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