In article <8l1dot$flg$1@nnrp1.deja.com>,
  Dietmar Kuehl <dietmar_kuehl@yahoo.com> wrote:
>
> String collation and character classification are completely separated
> and there is no association between them. Correspondingly there is no
> way to access a facet from the same locale. This applies to all
> facets, not just to the 'ctype' and 'collate' facets.

Thanks Dietmar,

I've come to the same conclusion. However I see this as a practical
deficiency in the design.

My use case is that I derive from std::collate in order to implement a
case insentive compare method. Therefore I access std::ctype::tolower to
perform the transform. This seems correct in concept. If I don't use the
same locale the operation looses coherency and may result in a
conversion error (like converting between code pages).

As you describe, numget and numput have this additional coherency via an
ios_base parameter. That this type of mechanism isn't generally applied
across all facets seems (to me) to be a design flaw.

Any help writing a case insensitive collate::compare() as described
above is greatly appreciated.

--
Regards, Marcus


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Hi All,

I've derived a class from the standard collate facet. Within its
implementation I need to refer to the locale the facet is bound to, in
order to access the associated ctype facet. I don't see a way to do
this. The facet constructor doesn't take a locale for example.

How is this type of derivation done properly?

--
Regards, Marcus


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Hi,
In article <8l09ki$mb7$1@nnrp1.deja.com>,
  Marcus Barnes <marcus_aurelius@my-deja.com> wrote:
> I've derived a class from the standard collate facet. Within its
> implementation I need to refer to the locale the facet is bound to, in
> order to access the associated ctype facet. I don't see a way to do
> this. The facet constructor doesn't take a locale for example.

String collation and character classification are completely separated
and there is no association between them. Correspondingly there is no
way to access a facet from the same locale. This applies to all facets,
not just to the 'ctype' and 'collate' facets. In some situations a
different facet is used to determine additional properties. In this
situation a locale is passed somehow to the corresponding methods, eg.
in case of the numeric facets (ie. 'num_put' and 'num_get') the methods
get passed in an 'ios_base' object from which additional facets (mainly
'numpunct' and 'ctype') are determined.
--
<mailto:dietmar_kuehl@yahoo.com>
<http://www.dietmar-kuehl.de/>


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