J3/05-206
Date: 10 Jun 2005
To: J3
From: Fred Tydeman
Subject: Accuracy of conversion of real literal constants
NUMBER: F03/0067
TITLE: Accuracy of conversion of real literal constants
KEYWORDS: conversion, accuracy
DEFECT TYPE: Interpretation
STATUS: For consideration
QUESTION:
The following is independent of IEEE-754.
Fortran 2003 10.6.1.2.6 covers conversions between "decimal values"
and "internal values" and has some strong requirements.
Are there equivalent requirements on accuracy for conversions of real
literal constants? Sections 4.1.2 and 4.4.2 seems like the places to
find them (if they exist).
What rounding mode is used for conversions of real literal constants?
Is the same rounding mode used for all such conversions?
The following four questions are about positive values, but the same
would apply to negative values.
Must all "decimal values" in the range smallest non-zero finite
internal value (which could be a denormal) to largest finite internal
value, e.g. 0.1, be converted?
Must all "decimal values" in the range zero to smallest non-zero
finite internal value, e.g. 1.0e-999999999, be converted?
Must all "decimal values" larger than the largest finite internal
value, e.g. 9.9e+99999999999, be converted if infinity is an internal
value? What does nearest rounding mean for these cases?
What requirements exist for "decimal values" larger than the largest
finite internal value if infinity is not an internal value?
ANSWER:
DISCUSSION:
EDITS:
SUBMITTED BY: Fred Tydeman
HISTORY: J3/05-206 m173 Submitted
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