uncover the call structure of a recursive function call

The recursive function to examine shall be y = f(x) , then the first call of f must be modified to: [y,tree] = f( x , recurse() ).
When f recursively calls itself use: y = f( x, recurse(tree) )
The call structure of f will be traced in an adjacency matrix "tree.glo.adjacency" by calling recurse(tree) together with f. The adjacency matrix can be plotted as a directed graph using the method RecursionStructure(tree).
As an example see the use of recurse(tree) in the karatsuba function.
run: "karatsubatest" in order to multiply two large integers using the karatsuba method.