Issue 0CFP.08: Part 2: Editorial clarification about number digits in the coefficient

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Authors: WG14, Jim Thomas
Date: 2016-09-10
Reference document: N2077
Submitted against: Floating-point TS 18661 (C11 version, 2014-2016)
Status: Fixed
Fixed in: C23
Converted from: n2397.htm

Summary

Summary

In 12.5, n is defined to be “the number of digits in the coefficient c”, where the decimal floating-point argument is represented by the triple (s, c, q). The intention is that n is the number of digits in the coefficient of the particular argument, i.e., the number of significant digits, not the maximum number of digits in the coefficient for the type. This might be misread, particularly since 5.2.4.2.2a says

number of digits in the coefficient

DEC32_MANT_DIG                 7
DEC64_MANT_DIG                 16
DEC128_MANT_DIG                34

This part of 5.2.4.2.2a is in the context of characterizing the type, so clearly refers to the type and not any particular representation.

Suggested Technical Corrigendum

In 12.5, change:

where n is the number of digits in the coefficient c

to:

where n is the number of significant digits in the coefficient c


Comment from WG14 on 2018-10-18:

Oct 2016 meeting

Committee Discussion

The committee agrees that this is a defect and accepts the Suggested Technical Corrigendum

Proposed Technical Corrigendum

In 12.5, change:

where n is the number of digits in the coefficient c

to:

where n is the number of significant digits in the coefficient c