Re: [Boost-users] Need help with Errors in boost MPL, tutorials

Subject: Re: [Boost-users] Need help with Errors in boost MPL, tutorials
From: Philipp Moeller (philipp.moeller_at_[hidden])
Date: 2012-01-24 12:10:28

Linh Ha <lha_at_[hidden]> writes:

>> Just on a first glance, looks like you're mistaking ::_1 (placeholder from
>> Boost.Bind) for boost::mpl::_1 (placeholder from Boost.MPL). They're
>> incompatible; try using the latter...?
>>
>> - Jeff
>
> Thanks, Jeff !
>
> It works. But then my next question is why they are different and
> somehow incompatible even-though are both placeholders. Why we keep
> two different place holder if they do exactly a same functionality.

There are far more than just two placeholders in Boost. AFAIK Phoenix,
Lambda and Bind come with their own. The mpl placeholder is different
though: It is a placeholder for a type (it's a meta-programming library
after all) and not for a value. Try to write a MPL lambda, that might
clear up some of the confusion.

-- 
Philipp Moeller, GeometryFactory