C Interfaces and Implementations: Techniques for Creating Reusable Software

Chapter 18. Arbitrary-Precision Arithmetic

This chapter describes the AP interface, which provides signed integers of arbitrary precision and arithmetic operations on them. That is, unlike XP_Ts, the integers provided by AP can be negative or positive, and they can have an arbitrary number of digits. The values that can be represented are limited only by the available memory. These integers can be used in applications that need integer values in a potentially huge range. For example, some mutual-fund companies track share prices to the nearest centicent — 1/10,000 of a dollar — and thus might do all computations in centicents. A 32-bit unsigned integer can represent only $429,496.7295, which is only a tiny fraction of the billions of dollars held ...