Re: [Boost-users] more lambda issues

From: Noah Roberts (roberts.noah_at_[hidden])
Date: 2006-11-30 12:38:27

On 11/30/06, Joaquín Mª López Muñoz <joaquin_at_[hidden]> wrote:

> > bind( &deref_val_type::f, *_1 ) == 5 may work with Lambda.
>
> Almost: the translation of the expression to the lambda world, i.e.
>
>   l::bind( &deref_val_type::f, *l::_1 ) == 5
>
> (assuming namespace l = boost::lambda) fails to compile because
> it indices the declaration of
>
>   boost::tuples::cons<deref_val_type, boost::tuples::null_type>::head
>
> which is not instantiable deref_val_type is abstract.

Right, works fine until working with abstract types.  Kind of
frustrating to toss it into a test with mock objects and not realize
you also need to test that your algorithms work with abstract
interfaces.

 The closest I
> can get in BLL to your formulation is:
>
>   l::bind( &deref_val_type::f, &*l::_1 ) == 5
>
> which works as expected.

Yep, that works.  Not exactly what I wanted to see, and I should have
thought of it, but there it is.  I think this is something the lambda
folks might want to work on as it isn't exactly favorable (is it in
the works?).  Bind is a lot easier to work with because it catches on.