Re: [boost] [convert] Version in the Vault ready for review.

Subject: Re: [boost] [convert] Version in the Vault ready for review.
From: David Abrahams (dave_at_[hidden])
Date: 2009-04-13 17:54:24

on Thu Apr 09 2009, Gottlob Frege <gottlobfrege-AT-gmail.com> wrote:

> Case 'C' is problematic - let's get rid of it:
>        i = from(str, res);
> is difficult when the type is NOT default constructible.  So let's get
> rid of it.
> If you want a status result, supply a default (case D):
>       i = from(str, 0, res);
>
> *Alternatively*, since we know the type, we could probably use some
> type-inference tricks to only allow case C to compile when the type is
> default constructible:
>
> C1:
>     int i = convert<int>::from(str, res);   // OK
>
> - compiles as int is default constructible.
> - does NOT throw as you get status back in res.
>
> C2:
>    class C { public: C(int, int); };
>    C c = convert<int>::from(str, res);  // does NOT compile
>    C c = convert<int>::from(str, C(1, 2), res);  // default required

You might want to take a look at
http://www.boost.org/doc/libs/1_38_0/libs/python/doc/v2/extract.html
which had to solve some of the same problems.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com