Higher-order Chemical Programming Style

The chemical reaction metaphor describes computation in terms of a chemical solution in which molecules interact freely according to reaction rules. Chemical solutions are represented by multisets of elements and computation proceeds by consuming and producing new elements according to reaction conditions and transformation rules. The chemical programming style allows to write many programs in a very elegant way. We go one step further by extending the model so that rewrite rules are themselves molecules. This higher-order extension leads to a programming style where the implementation of new features amounts to adding new active molecules in the solution representing the system