Computer arithmetic is a specialist field of study, and it is very difficult for designers to choose the most efficient method for implementing a given algorithm due to the large number of design choices available. In this paper, an object oriented arithmetic library is presented which can be used to simulate and generate designs which use fixed, floating, logarithmic and hybrid number representations. The advantages of this approach are that a user can explore trade-offs concerning precision, accuracy and speed from single high level description. Furthermore, users need not be intimately familiar with the implementation details of the underlying libraries, thus allowing users to develop systems employing advanced computer arithmetic without detailed knowledge of its implementation. The application of this library to a coprocessor which implements the force pipeline for an N-body solver is described.