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

Returns the epsilon of the quantity

== Synopsis

Declared in `<mp‐units/math.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename Rep,
    xref:mp_units/Reference.adoc[Reference] R>
requires RepresentationOf<Rep, get_quantity_spec(R{})> && requires { std::numeric_limits<Rep>::epsilon(); }
[[deprecated("2.5.0: Use `std::numeric_limits<Quantity>::epsilon()` instead"), nodiscard]]
constexpr
xref:mp_units/quantity-01.adoc[quantity<R{}, Rep>]
epsilon(R r) noexcept;
----

[WARNING]
====
https://en.cppreference.com/cpp/language/attributes/deprecated[Deprecated^]: 2.5.0: Use `std::numeric_limits<Quantity>::epsilon()` instead. Use of this entity is allowed but discouraged.
====
== Description

The returned value is defined by a .

== Return Value

Quantity The epsilon value for quantity's representation type

[NOTE]
====
The return value https://en.cppreference.com/cpp/language/attributes/nodiscard[should not be discarded^].
====
== Template Parameters

[cols="1,4"]
|===
| Name| Description
| *Q*
| Quantity type being the base of the operation
|===


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