#ifndef MTL_ELT_H#define MTL_ELT_Htemplate <class Tnum, class Index>class elt {  typedef elt<Tnum,Index> self;public:  inline elt(const self& x)     : value_(x.value_), row_(x.row_), column_(x.column_) { }  inline elt(Tnum& v, const Index& i, const Index& j)    : value_(v), row_(i), column_(j) { }  inline self& operator=(const self& x) {    value_ = x.value_; row_ = x.row_; column_ = x.column_;    return *this;  }  inline self& operator=(const Tnum& v) { value_ = v; return *this; }  inline operator Tnum&() { return value_; }  inline Index row() { return row_; }  inline Index column() { return column_; }protected:  Tnum& value_;  Index row_;  Index column_;};#endif