Hi folks, I've run into a tricky problem when using stl map, and am hoping someone might be able to point me on the right direction.
I have a map of airports, indexed by string, which is the ICAO code: map<string, ARP*> apt_map; Now, I want to emulate the 'search ahead' function of GPS code entry, so that, for instance, entering "KC" will cause "KCAD" to be displayed - the first airport in the database starting with "KC". To do this I use the lower_bound function, for both "KC" and "KD". If the returned iterators don't match, then there is a valid match for "KC". map<string, ARP*>::iterator it1, it2; it1 = apt_map.lower_bound("KC"); it2 = apt_map.lower_bound("KD"); return(it1 == it2 ? NULL : it1->second); So far, so good. Now, the problem is that the KLN89 (and probably most/all GPS units) regards A->Z as coming before 0->9, whereas the standard string compare function regards 0->9 as coming before A->Z. So in this instance I might get "KC52" displayed instead of "KCAD" (there isn't really a KC52, but there are many examples outside the US where this bites). Now, I can get round this by using a comparison of lower_bound tests for "KC", "KCA" and "KD", and it works. Unfortunately I then have to check for non-alpha chars down to the end of the returned string, and re-test any with 'A' substituted in place. It's effective, but really ugly! I had to think quite hard about code I only wrote a week ago to compose the last sentence, and that's always a bad sign. What I'm sure I ought to be able to do is to define a custom comparison operator that performs a string comparison where numbers are considered to come after letters, and for good measure to do a case-insensitive match on the letters. I want to be able to do something like: it1 = apt_map.lower_bound("KC", gps_less); with all the ugly bits tucked away in gps_less which I can get working and them forget about. Unfortunately, I can't find any good example in any of my books to do this, nor on the internet, and everything I try is giving me swathes of typical gruesome-to-mentally-parse stl error messages. If anyone has an example of how to do this, or any pointers to one, I'd be most grateful. Cheers - Dave _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d