This issue has been automatically converted from the original issue lists and some formatting may not have been preserved.
Authors: Thomas Plum, Project Editor (P.J. Plauger)
Date: 1993-04-15
Submitted against: C90
Status: Closed
Cross-references: 0063
Converted from: dr.htm, dr_056.html
The following requirement is implied in several places, but not explicitly stated. It should be explicitly affirmed, or alternative wording adopted.
The representation of floating-point values (such as floating-point constants,
the results of floating-point expressions, and floating-point values returned by
library functions) shall be accurate to one unit in the last position, as
defined in the implementation's <float.h> header.
Discussion: The values in <float.h> aren't required to document the underlying
bitwise representations. If you want to know how many bits, or bytes, a
floating-point values occupies, use sizeof. The <float.h> values document
the mathematical properties of the representation, the behaviors that the
programmer can count upon in analyzing algorithms.
It is a quality-of-implementation question as to whether the implementation
delivers accurate bits throughout the bitwise representation, or alternatively,
delivers considerably less accuracy. The point being clarified is that
<float.h> documents the delivered precision, not the theoretically possible
precision.
Comment from WG14 on 1997-09-23:
Open Issue