Variable precision exponential function

• Authors: T. E. Hull;A. Abrham
• Venue: ACM Transactions on Mathematical Software (TOMS)
• Year: 1986

The exponential function presented here returns a result which differs from ex by less than one unit in the last place, for any representable value of x which is not too close to values for which ex would overflow or underflow. (For values of x which are not within this range, an error condition is raised.) It is a 聯variable precision聰 function in that it returns a p-digit approximation for a p-digit argument, for any p = 0 (p-digit means p-decimal-digit). The program and analysis are valid for all p = 0, but current implementations place a restriction on p. The program is presented in a Pascal-like programming language called Numerical Turing which has special facilities for scientific computing, including precision control, directed roundings, and built-in functions for getting and setting exponents.