std::vector<T,Allocator>::at
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| reference       at( size_type pos ); | ||
| const_reference at( size_type pos ) const; | ||
Returns a reference to the element at specified location pos, with bounds checking. 
If pos is not within the range of the container, an exception of type std::out_of_range is thrown.
Parameters
| pos | - | position of the element to return | 
Return value
Reference to the requested element.
Exceptions
std::out_of_range if !(pos < size()).
Complexity
Constant.
See also
| access  specified element (public member function) |