A Language for Specifying Recursive Traversals of Object Structures

We present a domain-specific language for specifying recursive traversals of object structures, for use with the visitor pattern. Traversals are traditionally specified as iterations, forcing the programmer to adopt an imperative style, or are hard-coded into the program or visitor. Our proposal allows a number of problems best approached by recursive means to be tackled with the visitor pattern, while retaining the benefits of a separate traversal specification. Keywords: Visitor Pattern, Recursive Programming, Separation of Concerns 1 Introduction The visitor pattern [GHJV95] allows a programmer to write behavior that traverses an object structure without embedding assumptions about the structure into the computational code. This is a result of separating navigational code from code that performs the computation. In most versions of the visitor pattern, the exact sequence in which parts of an object are visited is hard-coded, either into the object or into the visitor. We refer to ..