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

Linear interpolation or extrapolation

== Synopsis

Declared in `<mp‐units/math.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    auto R1,
    auto Origin,
    typename Rep1,
    auto R2,
    typename Rep2,
    typename Factor>
requires requires(Rep1 a, Rep2 b, Factor t) {
    get_common_reference(R1, R2);
    requires requires { lerp(a, b, t); } || requires { std::lerp(a, b, t); };
  }
[[nodiscard]]
constexpr
xref:mp_units/QuantityPointOf.adoc[QuantityPointOf<get_quantity_spec(get_common_reference(R1, R2))>] auto
lerp(
    xref:mp_units/quantity_point-08.adoc[quantity_point<R1, Origin, Rep1>] const& a,
    xref:mp_units/quantity_point-08.adoc[quantity_point<R2, Origin, Rep2>] const& b,
    Factor const& t) noexcept;
----

== Description

Computes the linear interpolation between `a` and `b`, if the parameter `t` is inside `[​0​, 1)` (the linear extrapolation otherwise), i.e. the result of `a + t(b − a)` with accounting for floating‐point calculation imprecision.

== Parameters

[cols=2]
|===
| Name
| Description
| *a*
| A quantity point
| *b*
| A quantity point
|===


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