Re: [Boost-users] [mpl][type_traits] Transforming to common type

Subject: Re: [Boost-users] [mpl][type_traits] Transforming to common type
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2014-02-22 10:55:13

AMDG

On 02/22/2014 05:25 AM, Bjorn Reese wrote:
> <snip>
> /usr/local/include/boost/type_traits/common_type.hpp:111:42: error:
> incompatible operand types ('mpl_::arg<1>' and 'int')
>   typedef decltype(declval<bool>() ? declval<T>() : declval<U>()) type;
>                                    ^ ~~~~~~~~~~~~   ~~~~~~~~~~~~
> 
> It appears that the placeholder is not expanded to its actual type.
> 

Don't use ::type in MPL Lambda expressions.
It forces immediate evaluation, which is
not what you want.

> 
> <snip>
>         boost::common_type<boost::mpl::_1, int>::type
> <snip>
> 

In Christ,
Steven Watanabe