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

A transparent wrapper that carries an error policy for domain constraint enforcement.

== Synopsis

Declared in `<mp‐units/constrained.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename T,
    typename ErrorPolicy = xref:mp_units/throw_policy.adoc[throw_policy]>
class constrained;
----

== Description

This wrapper does not check anything itself. It serves as a signal to the mp‐units library that domain constraint violations should be reported via the ErrorPolicy rather than through precondition checks.

All arithmetic operations are forwarded to the underlying type T.

== Types

[cols=1]
|===
| Name
| xref:mp_units/constrained/error_policy.adoc[`error_policy`] 
| xref:mp_units/constrained/value_type.adoc[`value_type`] 
|===

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:mp_units/constrained/2constructor-00.adoc[`constrained`]         [.small]#[constructor]#
| Constructors
| xref:mp_units/constrained/operator_mod_eq.adoc[`operator%=`] 
| Modulus assignment operator
| xref:mp_units/constrained/operator_star_eq.adoc[`operator*=`] 
| Multiplication assignment operator
| xref:mp_units/constrained/operator_inc-0f.adoc[`operator++`] 
| Increment operators
| xref:mp_units/constrained/operator_plus_eq.adoc[`operator+=`] 
| Addition assignment operator
| xref:mp_units/constrained/operator_dec-0f.adoc[`operator‐‐`] 
| Decrement operators
| xref:mp_units/constrained/operator_minus_eq.adoc[`operator‐=`] 
| Subtraction assignment operator
| xref:mp_units/constrained/operator_slash_eq.adoc[`operator/=`] 
| Division assignment operator
| xref:mp_units/constrained/value.adoc[`value`] 
| 
| xref:mp_units/constrained/2conversion.adoc[`operator T`] 
| Conversion to `T`
|===

== Data Members

[cols=1]
|===
| Name
| xref:mp_units/constrained/value_.adoc[`value_`] 
|===

== Friends

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

| `xref:mp_units/operator_minus-0e.adoc[mp_units::operator‐]`
| Unary minus operator
| `xref:mp_units/operator_plus-08.adoc[mp_units::operator+]`
| Unary plus operator
|===

== Template Parameters

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

| *T*
| the underlying representation type
| *ErrorPolicy*
| policy type providing static on_constraint_violation(const char*)
|===


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