The iterator constructor X(i,j) for containers as defined in 23.1.1 and
23.2.2 does only require that i and j must be input iterators but
nothing is said about their associated value. There are three sensible
options:

1. iterator's value_type is exactly X::value_type (modulo cv).
2. iterator's value_type is *implicitly* convertible to X::value_type.
3. iterator's value_type is *explicitly* convertible to X::value_type.

The issue has practical implications, and stdlib vendors have
taken divergent approaches to it: Dinkumware follows 2,
libstdc++ follows 3.

The problem was already mentioned by Dietmar Kuehl as far
back as 2001 (see http://tinyurl.com/86sbo about at the
end of the message), but I haven't been able to found any
reference to it in the commitee issues list. Does anyone know
what the status of this is?

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In article <1134737901.692065.312650@o13g2000cwo.googlegroups.com>,
 "Joaqu=EDn M L=F3pez Mu=F1oz" <joaquin@tid.es> wrote:

> The iterator constructor X(i,j) for containers as defined in 23.1.1 and
> 23.2.2 does only require that i and j must be input iterators but
> nothing is said about their associated value. There are three sensible
> options:
>=20
> 1. iterator's value_type is exactly X::value_type (modulo cv).
> 2. iterator's value_type is *implicitly* convertible to X::value_type.
> 3. iterator's value_type is *explicitly* convertible to X::value_type.
>=20
> The issue has practical implications, and stdlib vendors have
> taken divergent approaches to it: Dinkumware follows 2,
> libstdc++ follows 3.
>=20
> The problem was already mentioned by Dietmar Kuehl as far
> back as 2001 (see http://tinyurl.com/86sbo about at the
> end of the message), but I haven't been able to found any
> reference to it in the commitee issues list. Does anyone know
> what the status of this is?

To the best of my knowledge this issue has not come before the lwg.

-Howard

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