# AINF 3 "12 June 2000" "Version 1.00"

## Table of contents

- NAME
- SYNOPSIS
- DESCRIPTION
- SEE ALSO
- AUTHORS

# NAME

ainf - Single-precision +Infinity

# SYNOPSIS

Fortran (77, 90, 95, HPF):

> f77 [ flags ] file(s) ... -L/usr/local/lib -lgjl

> >     REAL FUNCTION ainf()

C (K&R, 89, 99), C++ (98):

> cc [ flags ] -I/usr/local/include file(s) ... -L/usr/local/lib -lgjl
> Use

> > #include <gampsi.h>

> to get this prototype:

> > fortran_real ainf(void);

NB: The definition of C/C++ data types fortran_ xxx, and the mapping of Fortran external names to C/C++ external names, is handled by the C/C++ header file. That way, the same function or subroutine name can be used in C, C++, and Fortran code, independent of compiler conventions for mangling of external names in these programming languages.

Last code modification: 12-Jun-2000

# DESCRIPTION

Return single-precision +Infinity, or else on non-IEEE 754 systems, the largest representable floating-point number.

For IEEE 754 systems, each call to this function intentionally produces a trappable zero divide, rather than saving the computed value on the first call, and then just returning the saved value on subsequent calls.

This function exists because of at least one abberant software implementation of quadruple-precision arithmetic (on IBM RS/6000 AIX 4.x), which produces NaN, instead of Infinity, for the square of large numbers. Fortunately, it correctly produces Infinity for 1.0/0.0, so that is how we generate it here.

Relegating the computation of Infinity to a separate function also provides a convenient single debugger breakpoint location.

# SEE ALSO

dinf(3), qinf(3), isainf(3), isdinf(3), isqinf(3).

# AUTHORS

The algorithms and code are described in detail in the paper

> Algorithm xxx: Quadruple-Precision Gamma(x) and psi(x) Functions for Real Arguments

in ACM Transactions on Mathematical Software, Volume ??, Number ??, Pages ????--???? and ????--????, 2001, by

>     Nelson H. F. Beebe
>     Center for Scientific Computing
>     University of Utah
>     Department of Mathematics, 110 LCB
>     155 S 1400 E RM 233
>     Salt Lake City, UT 84112-0090
>     Tel: +1 801 581 5254
>     FAX: +1 801 581 4148
>     Email: beebe@math.utah.edu, beebe@acm.org, beebe@computer.org
>     WWW URL: http://www.math.utah.edu/~beebe

and

>     James S. Ball
>     University of Utah
>     Department of Physics
>     Salt Lake City, UT 84112-0830
>     USA
>     Tel: +1 801 581 8397
>     FAX: +1 801 581 6256
>     Email: ball@physics.utah.edu
>     WWW URL: http://www.physics.utah.edu/people/faculty/ball.html