[boost] Re: [MPL] unlambda primitive

From: Joel (joel_at_[hidden])
Date: 2005-01-06 19:04:38

Aleksey Gurtovoy wrote:
> Joel writes:
> 
>>write a lambda expression that accepts:
>>
>>    1. a 2-dimensional container (e.g. vector<vector<int> >)
>>    2. a container element (e.g. int)
>>
>>and pushes-back the element to each of the vector<int>.
>>
>>Solution:
>>
>>for_each(_1,
>>     lambda(_a = _2)
>>     [
>>         push_back(_1, _a)
>>     ]
>>)
>>
>>Since we do not have access to the arguments of the outer scopes
>>beyond the lambda-body, we introduce a local variable _a that
>>captures the second outer argument: _2. Hence: _a = _2. This
>>local variable is visible inside the lambda scope.
> 
> 
> Any particular reason why you decided against implicit scoping along
> the lines of
> 
>     for_each( _1, push_back(_1, outer(_2)) )

Actually, both solutions are orthogonal. I still have the
code for "outer". I just don't have it documented yet.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net