Two exercises found in a book on algorithmics
Richard S. Bird, Lambert Meertens · 1987
I. INTRODUCTION. A major test of a good notation is how suggestive it is of new relationships between the objects described, and how susceptible it is to the manipulations required to establish such relationships formally. Indeed, if the associated calculus is sufficiently attractive to use, new relationships can come to light simply by the process of manipulating formulae.