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 <boost/lambda/lambda.hpp> #include <algorithm> #include <list>

using namespace std; using namespace boost::lambda;

int main() { int count = 0; list<list<int> > 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?

AFAICT, no. Not unless the type of _1 implements all possible member functions in the world :-) This is the single biggest problem of a non-langauage solution to lambdas. -Thorsten

On 2/1/06, Daniel Lidström <daniel.lidstrom@sbg.se> 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 <boost/lambda/lambda.hpp> #include <algorithm> #include <list>

using namespace std; using namespace boost::lambda;

int main() { int count = 0; list<list<int> > 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