Implementation

Here is the implementation of the rubber-sheet transformation.

The definition of covarianceBlock, which makes a row of blocks as in , is probably the only one that may need some explanation. For example, let us make the matrix for u and {v1,v2} with the help of Thread.

Next we apply h on the two blocks at the right level.

Finally we flatten to get a matrix.

To make this code work for a concrete vector , as well as for a symbol , we first introduce a free variable x instead of u and then use the substitution xu. This variable has been made local with the use of Module. All together we obtain covarianceBlock.