template<typename Derived>
class Eigen::SolverBase< Derived >
A base class for matrix decomposition and solvers.
 Template Parameters

Derived  the actual type of the decomposition/solver. 
Any matrix decomposition inheriting this base class provide the following API:
MatrixType A, b, x;
DecompositionType dec(A);
x = dec.solve(b);
x = dec.transpose().solve(b);
x = dec.adjoint().solve(b);
 Warning
 Currently, any other usage of transpose() and adjoint() are not supported and will produce compilation errors.
 See also
 class PartialPivLU, class FullPivLU