>>> Given an array of businesses with latitude/longitude coordinates, and the >>> user's location, sort the array of businesses by closest to the user.
A slight language digression: Oh my, if you saw how easy that was to do on an iPhone in ObjC (hundreds of locations). And then visualize it all on a google map with a detail view of everyone of those locations. With data updated in real-time. With a 5,000 mile server round trip. And do it all in a blink of the eye. (plus you get to talk to 4 orbiting satellites at the same time). Yummy! :-) Code in action here: (dropping, sorted pins by user location 1/2 way through). http://www.youtube.com/watch?v=krF9IUyF3Rw On Fri, Jul 16, 2010 at 4:36 PM, John Campbell <jcampbe...@gmail.com> wrote: > On Fri, Jul 16, 2010 at 2:48 PM, Hans Zaunere <li...@zaunere.com> wrote: >> Closures - great for Javascript, but for PHP? In a non-callback-centric >> synchronous language such as PHP, what else can we use this "syntactic >> sugar" for? How are people using them and what can we gain from them? And, >> the hell with code reuse? > > I have a favorite problem, that is hard/ugly to solve without closures: > > Given an array of businesses with latitude/longitude coordinates, and > the user's location, sort the array of businesses by closest to the > user. > > so you have: > > $stores = array( > array('name' => 'Pet Smart', 'lat'=>24.12, 'lon' => 54.23), > array('name' => 'Cats and Critter', 'lat'=>24.19, 'lon' => 54.32), > array('name' => 'Snakes and such', 'lat'=>24.45, 'lon' => 53.35), > array('name' => 'Lots of llams', 'lat'=>24.46, 'lon' => 54.97)); > > $user_location = array('lat'=> 24.45, 'lon' => 54.96); > > // Solution using closures > > // geo sort. > function sort_by_closest(&$points,$location) { > usort($points, function($a,$b) use($location) { > return distance($a,$location) > distance($b,$location); > }); > } > > // geo distance using sperical law of cosines. > function distance($a,$b) { > $R = 6371; // km > $d2r = pi() / 180; > return acos(sin($a['lat']*$d2r)*sin($b['lat']*$d2r) + > cos($a['lat']*$d2r)*cos($b['lat']*$d2r) * > cos($b['lon']*$d2r-$a['lon']*$d2r)) * $R; > } > > print_r($stores); > sort_by_closest($stores,$user_location); > print_r($stores); > > > -John > _______________________________________________ > New York PHP Users Group Community Talk Mailing List > http://lists.nyphp.org/mailman/listinfo/talk > > http://www.nyphp.org/Show-Participation > -- IM/iChat: ejpusa Links: http://del.icio.us/ejpusa Follow me: http://www.twitter.com/ejpusa Karma: http://www.coderswithconscience.com _______________________________________________ New York PHP Users Group Community Talk Mailing List http://lists.nyphp.org/mailman/listinfo/talk http://www.nyphp.org/Show-Participation
