[#mp_units-operator_lshift-0d9]
= xref:mp_units.adoc[mp_units]::operator<<
:relfileprefix: ../
:mrdocs:

Stream insertion operator

== Synopsis

Declared in `<mp‐units/framework/quantity_point.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename CharT,
    typename Traits,
    auto R,
    auto PO,
    typename Rep>
requires (PO == default_point_origin(R))
std::basic_ostream<CharT, Traits>&
operator<<(
    std::basic_ostream<CharT, Traits>& os,
    xref:mp_units/quantity_point-08.adoc[quantity_point<R, PO, Rep>] const& qp)
requires requires { os << qp.quantity_from_zero(); };
----

[NOTE]
====
This function is a https://en.cppreference.com/w/cpp/language/friend[hidden friend] of xref:mp_units/quantity_point-08.adoc[quantity_point], declared inside an implementation-defined base class: it can be found only through argument-dependent lookup.
====

== Return Value

Reference to the current output stream

== Parameters

[cols="1,4"]
|===
| Name| Description
| *os*
| An output stream
| *qp*
| The object to output
|===


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