Re: [boost] traversing boost::tuple

From: Maxim Yanchenko (maximyanchenko_at_[hidden])
Date: 2008-04-09 04:24:03

Emre Turkay <emreturkay <at> gmail.com> writes:

> Is there a way to traverse a boost::tuple at compile or runtime with sth
> similar to foreach?

Hi Emre,

If you can't use boost::fusion, you can declare something like this (didn't try 
myself):
template<class Tuple, class Func>
struct tuple_binder
{
  Tuple& t_;
  Func f_;
  tuple_binder(Tuple& t, const Func& f)
    : t_(t), f_(f) {}
  
  template< typename Number > void operator()(Number)
  {
    f_( t_.template get<Number::value>() );
  }
};

template<class Tuple, class Func>
inline
tuple_binder<Tuple, Func>
bind_tuple(Tuple& t, const Func& f)
{
  return tuple_binder<Tuple, Func>(t,f);
}

and then use boost::mpl::for_each in the following manner:

  MyTuple tuple;
  typedef boost::mpl::range_c< int,
                               0,
                               boost::tuples::length<MyTuple>::value
                             > Indices;
  
  boost::mpl::for_each< Indices >( bind_tuple( tuple, functor ) );

The idea is to iterate by tuple element indices (so you can iterate in any 
direction etc, just provide a desired index sequence it boost::mpl::for_each).

Bests,
Maxim