[Boost-users] Lambda library if_then question

I have a function which check the x of a RectList if it matches certain value, it put the y in an int vector, like this. class Rect{ int x; int y; }; typedef list RectList; // this compiles: void addKey(RectList& rectList, vector<int>& keys, int value) { for (RectList::iterator itr = rectList.begin(); itr != rectList.end(); itr++) { Rect* r = (*itr); if (r->x == value) { keys.push_back(r->y); } } } But when I try to replace the code using boost lambda, I can't get it to compile. can you please tell me what am I missing? void addKey(RectList& rectList, vector<int>& keys, int value) { for_each(rectList.begin(), rectList.end(), if_then( bind (&Rect::x, _1) == value, deviantKey.push_back( bind (&Rect::y, _1) ))); } error: oid addDeviantKey(RectList&, std::vector&, int)': ../DeviantPatternMatcher.cpp:146: error: no matching function for call to 'std::vector::push_back(const boost::lambda::lambda_functor