[#mp_units-utility-constrained-operator_minus_eq]
= xref:mp_units.adoc[mp&lowbar;units]::xref:mp_units/utility.adoc[utility]::xref:mp_units/utility/constrained.adoc[constrained]::operator&hyphen;&equals;
:relfileprefix: ../../../
:mrdocs:

Subtraction assignment operator

== Synopsis

Declared in `&lt;mp&hyphen;units&sol;utility&sol;constrained&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
constexpr
xref:mp_units/utility/constrained.adoc[constrained]&
operator&hyphen;&equals;(xref:mp_units/utility/constrained.adoc[constrained] const& rhs)
requires requires(T&amp; a, const T b) &lcub;
      &lcub; a &hyphen;&equals; b &rcub; &hyphen;&gt; std&colon;&colon;same&lowbar;as&lt;T&amp;&gt;&semi;
    &rcub;;
----

== Return Value

Reference to the current object

== Parameters

[cols="1,4"]
|===
| Name| Description
| *rhs*
| The right operand
|===


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