[#bsl-operator_lt-00]
= xref:bsl.adoc[bsl]::operator<
:relfileprefix: ../
:mrdocs:

Return `true` if the specified `lhs` `optional` object is ordered before the specified `rhs`, and `false` otherwise. `lhs` is ordered before `rhs` if `lhs` is disengaged or `lhs.value()` is ordered before `rhs`. This function can be called in constant expressions only if `t_LHS_TYPE` is not allocator‐aware.

== Synopsis

Declared in `<bslstl_optional.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_LHS_TYPE,
    class t_RHS_TYPE>
constexpr
bool
operator<(
    xref:bsl/optional-072.adoc[bsl::optional<t_LHS_TYPE>] const& lhs,
    t_RHS_TYPE const& rhs);
----


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