Re: [boost] Re: [MPL] unlambda primitive

From: Aleksey Gurtovoy (agurtovoy_at_[hidden])
Date: 2005-01-06 08:58:00

Joel writes:
> Hi Aleksey,

Hi Joel,

>
> Currently, Phoenix has local variables, lambda and scopes.
> IMHO, Phoenix-2 has the best syntax yet that satisfies all
> requirements so far:
>
>      http://tinyurl.com/6qyqr
>
> Here's the solution to the use-case posed in the email
> exchanges above:
>
> 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)) )

?

-- 
Aleksey Gurtovoy
MetaCommunications Engineering