iterating over a tuple

26 Apr 2002

      I have a list of heterogeneous objects, e.g.

struct Foo {
  Foo(int v) : value_( v ) {}
  int value() const { return value_ ; }
  int value_;
};

struct Bar {
  Bar(int v) : value_( v ) {}
  int value() const { return value_ ; }
  int value_;
};

int main()
{
  Foo foo(3);
  Bar bar(7);
  typedef boost::tuple< Foo, Bar > MyTuple ;
  MyTuple my_tuple( foo, bar );
  return 0;
}

And now I want to have a function that can accumulate the value sof all the 
objects in the tuple, e.g. (pseudocode since my problem is exacly that I 
can't figure out how to  code this)

template < typename TypleType >
int accumulate_values(const TupleType& t)
{
  int acc = 0;
  for(int i = 0 ; i < t.size() ; ++i ) acc += (get< i >( t )).value();
}

Can I do this using mpl (mpl looks great but I can't figure out how to do 
this).

thanks, toon

iterating over a tuple

Toon Knapen