Thanks for the replies... However I forgot to put in my question that I am looking for a macro and not template if possible, and for a solution as elegant as BOOST_FOREACH, where you have to code as less as possible. It not (only :) ) that I am lazy to write, but I think the resulting code would be easier to read. furthermore: 1. exception... throwing the exception removes the complexity of writing but introduces the complexity of exception (writing code + runtime). 2. pointer... use cases I would like to avoid pointers, as I have other constraints to work with const references. I was thinking all the day about this little "handicap" of the std::map. One way would be to have the concept of invalid object of the map data type that could be returned to satisfy the constraint of the reference, and a "horrible" function like bool return; const data_type & data = map.find(key, bool) if( return ) { //use the data } With this approach is that the "return" variable has to be declared. with the form I proposed BOOST_CONSTMAPFIND(aStringMap, "key", data) { processResult( data ); } the problem is that I do not know how to detect the type of data knowing in the map object. I thought for the moment that BOOST_FOREACH would "automatically" declare the type in the container (using non-standard typeof for eg), but revisiting again BOOST_FOREACH documentation i see that it declares the type. vector<int> v; BOOST_FOREACH( int i, v) etc. so it seems that if I declare the type of the data, my job becomes easy, a sort of "problem solved" const map<string, Mytype> & mymap = getMap(); //I changed the order of variables BOOST_CONSTMAPFIND(const Mytype &data, "key", mymap) { processResult(data); } and pair for non-const BOOST_MAPFIND(Mytype &data, "key", mymap) probably with some trick (probably sthg. similar used in BOOST_FOREACH), one could merge theh two macros. I am now two tired, but will write tomorrow the macro, test it, and would be happy if boost would accept it into the macros family. -- rgrds, mobi phil being mobile, but including technology http://mobiphil.com