Re: [Boost-users] [MPL] 2 Newbie Questions

From: Ovanes Markarian (om_boost_at_[hidden])
Date: 2007-03-16 16:59:34

Just an addition to the second question...

Unfortunately, I forgot my MPL book at work :( 

But I remember, that in the chapter about physical quantities authors show
how to compare quantity types (one which is iniaital mpl::vector like
mpl::vector_c<int, 0, 1, 0, ...> and the other an instance of mpl::vector
which is produced as a result of function application (which logically also
results in the same template arguments but have different type)) this
chapter might help you.

With Kind Regards,
Ovanes.

-----Original Message-----
From: Ovanes Markarian [mailto:om_boost_at_[hidden]] 
Sent: Freitag, 16. März 2007 21:44
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [MPL] 2 Newbie Questions

BOOST_MPL_ASSERT operates on types, this also applies to mpl::or_

Try out:

#include <boost/mpl/bool.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/mpl/or.hpp>

BOOST_MPL_ASSERT((true_)); //true is not a bool value it is a type it has
underscore...

BOOST_MPL_ASSERT((
     mpl::or_(false_, 
              boost::is_same<CallerConstraints,
                             CodeConstraints::Ignore_Constraints>)
   )); //false_ also a type...

With Kind Regards,
Ovanes

-----Original Message-----
From: Scott Meyers [mailto:usenet_at_[hidden]]
Sent: Freitag, 16. März 2007 20:38
To: boost-users_at_[hidden]
Subject: [Boost-users] [MPL] 2 Newbie Questions

I'm trying to use the MPL for the first time, and I have two questions. 
  First, I want to use BOOST_MPL_ASSERT to say that at least one of two
conditions is true.  For the time being, one of the conditions is always
false, so this is what I've tried:

   BOOST_MPL_ASSERT((
     false
     ||
     boost::is_same<CallerConstraints,
                    CodeConstraints::Ignore_Constraints>
   ));

It won't compile, so I tried this:

   BOOST_MPL_ASSERT((
     mpl::or_(false,
              boost::is_same<CallerConstraints,
                             CodeConstraints::Ignore_Constraints>)
   ));

It won't compile either.  I'm guessing that I have to use mpl::false_ or
something in place of false, but that doesn't work either.  Can somebody
please tell me the proper way to say what I want to say?

My second question is about the existence of an MPL algorithm akin to the
STL algorithm includes.  Given two MPL vectors V1 and V2, I want to know if
all the types in V1 are also in V2.  I know about mpl::contains, but I can't
find mpl::includes.  Is there one, or do I need to write it myself?

I have the MPL book, so references to that are fine, in addition to anything
online.

Thanks,

Scott

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