simplifications in the ei_solve_impl system, factor out some boilerplate code
diff --git a/doc/snippets/FullPivLU_kernel.cpp b/doc/snippets/FullPivLU_kernel.cpp
index e01186d..7086e01 100644
--- a/doc/snippets/FullPivLU_kernel.cpp
+++ b/doc/snippets/FullPivLU_kernel.cpp
@@ -1,6 +1,6 @@
MatrixXf m = MatrixXf::Random(3,5);
cout << "Here is the matrix m:" << endl << m << endl;
-MatrixXf ker = m.lu().kernel();
+MatrixXf ker = m.fullPivLu().kernel();
cout << "Here is a matrix whose columns form a basis of the kernel of m:"
<< endl << ker << endl;
cout << "By definition of the kernel, m*ker is zero:"