  Concerning classical computational models able to express all the Primitive
Recursive Functions (PRF), there are interesting results regarding limits on
their algorithmic expressiveness or, equivalently, efficiency, namely the
ability to express algorithms with minimal computational cost. By introducing
the reversible programming model Forest, at our knowledge, we provide a first
study of analogous properties, adapted to the context of reversible
computational models that can represent all the functions in PRF. Firstly, we
show that Forest extends Matos' linear reversible computational model MSRL, the
very extension being a guaranteed terminating iteration that can be halted by
means of logical predicates. The consequence is that Forest is PRF complete,
because MSRL is. Secondly, we show that Forest is strictly algorithmically more
expressive than MSRL: it can encode a reversible algorithm for the minimum
between two integers in optimal time, while MSRL cannot.
