Fix bug #674: typo in documentation example for BiCGSTAB. They are now proper snippet files.

doc/snippets/BiCGSTAB_simple.cpp

@@ -0,0 +1,11 @@
+  int n = 10000;
+  VectorXd x(n), b(n);
+  SparseMatrix<double> A(n,n);
+  /* ... fill A and b ... */ 
+  BiCGSTAB<SparseMatrix<double> > solver;
+  solver.compute(A);
+  x = solver.solve(b);
+  std::cout << "#iterations:     " << solver.iterations() << std::endl;
+  std::cout << "estimated error: " << solver.error()      << std::endl;
+  /* ... update b ... */
+  x = solver.solve(b); // solve again

doc/snippets/BiCGSTAB_step_by_step.cpp

@@ -0,0 +1,14 @@
+  int n = 10000;
+  VectorXd x(n), b(n);
+  SparseMatrix<double> A(n,n);
+  /* ... fill A and b ... */ 
+  BiCGSTAB<SparseMatrix<double> > solver(A);
+  // start from a random solution
+  x = VectorXd::Random(n);
+  solver.setMaxIterations(1);
+  int i = 0;
+  do {
+    x = solver.solveWithGuess(b,x);
+    std::cout << i << " : " << solver.error() << std::endl;
+    ++i;
+  } while (solver.info()!=Success && i<100);

doc/snippets/compile_snippet.cpp.in

@@ -1,4 +1,4 @@
-#include <Eigen/Dense>
+#include <Eigen/Eigen>
 #include <iostream>
 
 using namespace Eigen;