//-----------------------------------------------------------------
//!
//! \brief value of last element
//!
//! Return the value of the last element in the linear view of
//! the array.
//!
//! \return value of last element
//!
value_type back() const { return _data.back(); }
//-----------------------------------------------------------------
//!
//! \brief reference to last element
//!
//! Return a reference to the last element in the linear view of
//! the array.
//!
//! \return reference to last element
//!
value_type &back() { return _data.back(); }