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

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

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename T,
    xref:mp_units/utility/ConstraintPolicy.adoc[ConstraintPolicy] ErrorPolicy = xref:mp_units/utility/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.

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:mp_units/utility/constrained/error_policy.adoc[`error_policy`] 
| The policy used to report domain constraint violations
| xref:mp_units/utility/constrained/value_type.adoc[`value_type`] 
| The underlying representation type
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:mp_units/utility/constrained/2constructor-0742.adoc[`constrained`]         [.small]#[constructor]#
| Constructors
| xref:mp_units/utility/constrained/operator_mod_eq.adoc[`operator%=`] 
| Assigns the wrapped value to its remainder with respect to `rhs.`
| xref:mp_units/utility/constrained/operator_star_eq.adoc[`operator*=`] 
| Multiplies the wrapped value by `rhs.`
| xref:mp_units/utility/constrained/operator_inc-0e.adoc[`operator++`] 
| Increment operators
| xref:mp_units/utility/constrained/operator_plus_eq.adoc[`operator+=`] 
| Adds `rhs` to the wrapped value.
| xref:mp_units/utility/constrained/operator_dec-0d4.adoc[`operator‐‐`] 
| Decrement operators
| xref:mp_units/utility/constrained/operator_minus_eq.adoc[`operator‐=`] 
| Subtracts `rhs` from the wrapped value.
| xref:mp_units/utility/constrained/operator_slash_eq.adoc[`operator/=`] 
| Divides the wrapped value by `rhs.`
| xref:mp_units/utility/constrained/value.adoc[`value`] 
| The wrapped underlying value.
| xref:mp_units/utility/constrained/2conversion.adoc[`operator T`] 
| Implicitly converts back to the underlying representation type.
|===


== Data Members

[cols="1,4"]
|===
| Name| Description
| xref:mp_units/utility/constrained/value_.adoc[`value_`] 
| The wrapped underlying value
|===


== Friends

[cols="1,4"]
|===
| Name| Description
| `xref:mp_units/utility/operator_minus-0d1.adoc[mp_units::utility::operator‐]`
| Negates the wrapped value
| `xref:mp_units/utility/operator_plus-0c.adoc[mp_units::utility::operator+]`
| Applies unary `+` to the wrapped value
|===

== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:mp_units/utility/operator_mod-0e.adoc[`operator%`]
| Computes the remainder of dividing a constrained value by a safe_int
| xref:mp_units/utility/operator_star-0b.adoc[`operator*`]
| Multiplies a constrained value by a safe_int
| xref:mp_units/utility/operator_star-0e4.adoc[`operator*`]
| Multiplies a safe_int by a non‐integral constrained value
| xref:mp_units/utility/operator_star-0e8.adoc[`operator*`]
| Multiplies a non‐integral constrained value by a safe_int
| xref:mp_units/utility/operator_plus-02.adoc[`operator+`]
| Adds a constrained value to a safe_int
| xref:mp_units/utility/operator_plus-06b.adoc[`operator+`]
| Adds a safe_int to a non‐integral constrained value
| xref:mp_units/utility/operator_plus-0fe8.adoc[`operator+`]
| Adds a non‐integral constrained value to a safe_int
| xref:mp_units/utility/operator_minus-01.adoc[`operator‐`]
| Subtracts a safe_int from a non‐integral constrained value
| xref:mp_units/utility/operator_minus-05.adoc[`operator‐`]
| Subtracts a safe_int from a constrained value
| xref:mp_units/utility/operator_minus-07.adoc[`operator‐`]
| Subtracts a non‐integral constrained value from a safe_int
| xref:mp_units/utility/operator_slash-04.adoc[`operator/`]
| Divides a non‐integral constrained value by a safe_int
| xref:mp_units/utility/operator_slash-082.adoc[`operator/`]
| Divides a safe_int by a non‐integral constrained value
| xref:mp_units/utility/operator_slash-08b.adoc[`operator/`]
| Divides a constrained value by a safe_int
|===

== Template Parameters

[cols="1,4"]
|===
| Name| Description
| *T*
| the underlying representation type
| *ErrorPolicy*
| policy type satisfying ConstraintPolicy (provides static on_constraint_violation(std::string_view))
|===


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