145. adjustfield lacks default value

Section: 30.5.5.2 [basic.ios.cons] Status: NAD Submitter: Angelika Langer Opened: 1999-05-12 Last modified: 2016-02-10

Priority: Not Prioritized

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Discussion:

There is no initial value for the adjustfield defined, although many people believe that the default adjustment were right. This is a common misunderstanding. The standard only defines that, if no adjustment is specified, all the predefined inserters must add fill characters before the actual value, which is "as if" the right flag were set. The flag itself need not be set.

When you implement a user-defined inserter you cannot rely on right being the default setting for the adjustfield. Instead, you must be prepared to find none of the flags set and must keep in mind that in this case you should make your inserter behave "as if" the right flag were set. This is surprising to many people and complicates matters more than necessary.

Unless there is a good reason why the adjustfield should not be initialized I would suggest to give it the default value that everybody expects anyway.

Rationale:

This is not a defect. It is deliberate that the default is no bits set. Consider Arabic or Hebrew, for example. See 25.4.2.2.2 [facet.num.put.virtuals] paragraph 19, Table 61 - Fill padding.