Eigen
3.3.4

Pseudo expression representing a solving operation.
Decomposition  the type of the matrix or decomposion object 
Rhstype  the type of the righthand side 
This class represents an expression of A.solve(B) and most of the time this is the only way it is used.
Inherits Eigen::SolveImpl< Decomposition, RhsType, internal::traits< RhsType >::StorageKind >.