// inverse
  cout << "inv(A) = " << endl << inv(A) << endl;
  double k = 1.23;

  mat    B = randu<mat>(5,5);
  mat    C = randu<mat>(5,5);

  rowvec r = randu<rowvec>(5);
  colvec q = randu<colvec>(5);


  // examples of some expressions
  // for which optimised implementations exist
  // optimised implementation of a trinary expression
  // that results in a scalar
  cout << "as_scalar( r*inv(diagmat(B))*q ) = ";
  cout << as_scalar( r*inv(diagmat(B))*q ) << endl;

  // example of an expression which is optimised
  // as a call to the dgemm() function in BLAS:
  cout << "k*trans(B)*C = " << endl << k*trans(B)*C;

    return 0;