Re: [Boost-users] boost::mpl::plus changes type

Subject: Re: [Boost-users] boost::mpl::plus changes type
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2011-04-09 22:02:22

AMDG

On 04/09/2011 06:38 PM, Peter Foelsche wrote:
> typename boost::mpl::at<
> typename boost::mpl::insert<
> boost::mpl::map<>,
> boost::mpl::pair<
> typename boost::mpl::plus<
> boost::mpl::long_<0>,
> boost::mpl::long_<1>
>  >::type,
> boost::mpl::long_<0>
>  >::type,
> boost::mpl::long_<1>
>> ::type
>
> I think this gives void_.
> In words (in case of I did something wrong):
> Insert a result from add into a map and then try to find it via at.
> It cannot be found anymore, as it is not a long_ but an integral_c now.
>

MPL in general gives no guarantee about the
exact types that operations produce.

In Christ,
Steven Watanabe