Docs: add section on resolving the aliasing issue.

2 files changed, 9 insertions, 0 deletions

diff --git a/doc/snippets/TopicAliasing_block.cpp b/doc/snippets/TopicAliasing_block.cpp
index 7d40cfafd..03282f4f0 100644
--- a/doc/snippets/TopicAliasing_block.cpp
+++ b/doc/snippets/TopicAliasing_block.cpp
@@ -1,5 +1,7 @@
 MatrixXi mat(3,3); 
 mat << 1, 2, 3,   4, 5, 6,   7, 8, 9;
 cout << "Here is the matrix mat:\n" << mat << endl;
+
+// This assignment shows the aliasing problem
 mat.bottomRightCorner(2,2) = mat.topLeftCorner(2,2);
 cout << "After the assignment, mat = \n" << mat << endl;
diff --git a/doc/snippets/TopicAliasing_block_correct.cpp b/doc/snippets/TopicAliasing_block_correct.cpp
new file mode 100644
index 000000000..6fee5801e
--- /dev/null
+++ b/doc/snippets/TopicAliasing_block_correct.cpp
@@ -0,0 +1,7 @@
+MatrixXi mat(3,3); 
+mat << 1, 2, 3,   4, 5, 6,   7, 8, 9;
+cout << "Here is the matrix mat:\n" << mat << endl;
+
+// The eval() solves the aliasing problem
+mat.bottomRightCorner(2,2) = mat.topLeftCorner(2,2).eval();
+cout << "After the assignment, mat = \n" << mat << endl;