Code Reuse With Transformation Objects

We present an approach for a lightweight datatype-generic programming in Objective Caml programming language aimed at better code reuse. We show that a large class of transformations usually expressed via recursive functions with pattern matching can be implemented using the single per-type traversal function and the set of objectencoded transformations, which we call transformation objects. Object encoding allows transformations to be modified, inherited and extended in a conventional object-oriented manner. However, the data representation is kept untouched which preserves the ability to construct and pattern-match it in the usual way. Our approach equally works for regular and polymorphic variant types [1] which makes it possible to combine data types and their transformations from statically typed and separately compiled components. We also present an implementation which allows to automatically derive most functionality from a slightly augmented type descriptions.