Re: [Boost-users] Using lambda to count elements in list of lists

1 Feb 2006

      On 2/1/06, Daniel Lidström  wrote:
...
Hello!
I'm trying to use Boost.Lambda to count the total number of elements
in a list of lists. This example shows what I'm trying to do:
#include 
#include <algorithm>
#include <list>
using namespace std;
using namespace boost::lambda;
int main()
{
   int count = 0;
   list ll;
   for_each(ll.begin(), ll.end(), var(count)+=(_1).size());
}
This will not compile: (13): error C2039: 'size': is not a member of
'boost::lambda::lambda_functor<T>'
Is this possible to do?
Thanks in advance!
Hälsningar,
Daniel
You'll need to use lambda's bind to access the size member function:

   for_each(ll.begin(), ll.end(), var(count)+=bind(&list<int>::size, _1));

You might might find std::accumulate a better match for your requirements:

   count = accumulate(ll.begin(), ll.end(), 0, _1 + bind(&list<int>::size, _2));

Stuart Dootson