For finite arguments, these functions shall return the value x, such that
x has a magnitude in the interval [0.5,1) or 0, and num equals
x times 2 raised to the power * exp.
If num is NaN, a NaN shall be returned, and the value of *exp is
If num is ±0, ±0 shall be returned, and the value of
*exp shall be 0.
If num is ±Inf, num shall be returned, and the value of *
exp is unspecified.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html