Assign to the object bound to first the value of the object bound to 'rhs.first', and return a reference offering modifiable access to this object. Note that this operations assigns through the reference, it does not rebind the reference.
first
Declared in <bslstl_pair.h>
<bslstl_pair.h>
Pair_First<TYPE&&>& operator=(Pair_First const& rhs) noexcept;