RE: [Boost-users] [BLL] How to search in a list for an object comparing a data member?

Gianluca Silvestri wrote:

Hi all, What I want to achieve is a code similar to this:

struct Foo { int fDataMember;}

int main() { std::vector<Foo> foos; Foo fo; std::find_if(foos.begin(), foos.end(), _1->fDataMember == fo.fDataMember); //<-- won't compile; }

Well, apart from the missing semi-colon, missing includes and missing closing brace, I imagine you're having trouble with "_1->fDataMember". This is a documented limitation of the lambda library - there is no way to defer lookup of member names (overloading -> just changes the type and value of the pointer used) so member access can't be done on a placeholder.

I know I could use a functor object but this is just an example for a more general need.

Sorry, you'll have to define functors. These template functor classes might be useful: template struct lookup_member_const { const V & operator()(const C & c) const { return c.*P; } }; template struct lookup_member { V & operator()(C & c) const { return c.*P; } }; Mind you, there might be similar things in Boost already.