Re: [boost] [local] this_ or _this?

Subject: Re: [boost] [local] this_ or _this?
From: Joel de Guzman (joel_at_[hidden])
Date: 2011-04-05 22:48:00

On 4/6/2011 8:01 AM, Steven Watanabe wrote:

>> 1) What is the exact definition of a "placeholder"?
>
> A placeholder is an object or type which
> is intended to be replaced by another
> object or type. Some Examples of placeholder
> objects are _1, _2, etc, used in bind, lambda,
> and phoenix. Examples of placeholder types
> are mpl::_1, and boost::recursive_variant_.

In phoenix, it is a placeholder because _this is supposed to
be replaced by /this/ when the function is evaluated and /this/
is a valid pointer at eval time. It is uses in, for example,
recursive lambda functions.

Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://boost-spirit.com