[Boost-users] Re: boost 1.32 breaks my code

From: David Abrahams (dave_at_[hidden])
Date: 2004-11-24 08:57:15

gast128 <gast128_at_[hidden]> writes:

> David Abrahams <dave <at> boost-consulting.com> writes:
>
>> 
>> "gast 128" <gast128 <at> hotmail.com> writes:
>> 
>> > First I get not BOOST_MPL_ASSERT compilable on VC 7.1. From the
>> > documentation I could read that it could replace
>> > BOOST_MPL_ASSERT_IS_SAME, but I removed it completely, and switched
>> > back to BOOST_STATIC_ASSERT.
>> 
>> Please post the code.
>> 
>
>
> That's simple:
>
>
> #include "boost/mpl/assert.hpp"
>
>
> void Testmpl6()
> {
>    BOOST_MPL_ASSERT(false);    //fails with error C2143: syntax error :  missing '}' before '('
>    BOOST_MPL_ASSERT((false));  //same error
> }

But neither of those is supposed to work.

    BOOST_MPL_ASSERT((<bool-valued-nullary-metafunction>))

is the only legal way to use this macro.  For example,

    BOOST_MPL_ASSERT((boost::mpl::false_))

which of course will fail to compile because the condition is false.

    BOOST_MPL_ASSERT((boost::mpl::true_))

will pass.

If you are replacing BOOST_MPL_ASSERT_IS_SAME(x, y) you need to write:

    BOOST_MPL_ASSERT((boost::is_same<x,y>))

Can you help me to understand what needs to be fixed in the
documentation so that this is clear?

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com