Defect Report #056
Submission Date: 15 Apr 93
Submittor: Project Editor (P.J. Plauger)
Source: Thomas Plum
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>
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
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