value::at (5 of 6 overloads)

Access an element, with bounds checking.

value&&
at(
    std::size_t pos,
    boost::source_location const& loc = BOOST_CURRENT_LOCATION) &&;

This function is used to access elements of the underlying array, or throw an exception if the value is not an array.

Constant.

Strong guarantee.

Name	Description
`pos`	A zero-based array index.
`loc`	`source_location` to use in thrown exception; the source location of the call site by default.

this->as_array(loc).at( pos, loc ).