Re: [Boost-Users] iterating over a tuple

27 Apr 2002


      On Friday 26 April 2002 01:37 pm, Aleksey Gurtovoy wrote:
...
Toon Knapen wrote:
...
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).
[snip Aleksey's solution]
...
Hope it's not too complicated :). LL might allow to do better on this one.
Thanks, I'll try it out. Coudl you enlighten me on how to solve it with the 
lambda library. I don't see how to iterate over the different indexes in 
combination with LL ?
t