Iterating over Boost fusion::vector

Question

I'm trying to iterate over a boost::fusion vector using:

typedef typename fusion::result_of::begin<T>::type t_iter;
  std::cout << distance(begin(t), end(t)) << std::endl;
  for(t_iter it = begin(t); it != end(t); next(it)){
    std::cout<<deref(it)<<std::endl;
  }

The distance cout statement gives me a finite length (2), however the loop seems to run indefinitely.

Any advice much appreciated!

Answer 1

You can't just iterate a Fusion vector like that, the type for each iterator may be different than the previous one (and usually is). I guess that's why you don't have it = next(it) in your code, it would give a compilation error.

You could use boost::fusion::for_each for this, together with a function object that prints each element to the standard output:

struct print
{
    template< typename T >
    void operator()( T& v ) const
    {
        std::cout << v;
    }
};

...

boost::fusion::for_each( t, print() );