Issue 0225: strtod, strtof and strtold expected form of the subject sequence

This issue has been automatically converted from the original issue lists and some formatting may not have been preserved.

Authors: Bill Plauger (US)
Date: 2000-04-10
Submitted against: C99
Status: Fixed
Fixed in: C99 TC2
Converted from: summary-c99.htm, dr_225.htm

Summary

In <stdlib.h>, functions strtod, strtof, and strtold should permit an implementation to recognize either inf or infinity, and either nan or nan(n-char-sequence_opt ), not just one of each.

Suggested Technical Corrigendum

In 7.20.1.3 replace:

• one of INF or INFINITY, ignoring case
• one of NAN or NAN(n-char-sequence_opt ), ignoring case in the NAN part, where:

with:

• either INF not followed by I, or INFINITY, ignoring case
• either NAN not followed by a left parenthesis, or NAN(n-char-sequence_opt ), ignoring case in the NAN part, where:

Comment from WG14 on 2001-09-18:

Committee Discussion (for history only)

For the functions strtod, strtof and strtold, should the implementation allow INFI to work as INF and leave the pointer at the next I, or should it reject a sequence such as INFINF as an invalid sequence, that failed at the second F.

The issue concerns what degree of pushback is necessary. But these are string functions, not input functions, so they do not need push back. Furthermore, 7.19.6.2¶9 and the associated footnote, clearly indicates that there is no requirement for the strto* functions to retain symmetric functionality with fscanf, indeed that is noted as being explicitly different.

It was noted that while symmetry with scanf may have some attractiveness, that the strto* functions cannot report that the input string did not match (no error mechanism exists) and that it would just return ZERO. With scanf the error is reported.

However, the issue in the DR really reduces to the use of the term one of on the bullets in 7.20.1.3¶3. The discussion indicated we were in agreement with Clive Feather's comments on this DR.

It was also observed that these changes also apply to the wcsto* functions in 7.24.4.1

Comment from WG14 on 2001-09-18:

Technical Corrigendum

Remove the words 'one of' from the third and fourth bullets of 7.20.1.3¶3.

Remove the words 'one of' from the third and fourth bullets of 7.24.4.1¶3.