Monday, September 18, 2006

Again, GoogleMaps seems it's an issue of latency. From a really fast connection it was able to recognize both Tokyo and Hong Kong. London is still un-geocodable though I am afraid.


I have recently started looking into Objective-C. In my experience, one of the biggest hurdles when learning C++ is understanding who does what; textbooks focus on OO and spend a lot of time on discussing buiding classes and coming up with silly examples, and little is said about how does this translate into executable code. With C you still have a pretty good idea how the code becomes machine code. With C++ the connection is broken; a class does not map to registries and you are left with a major gap in the continuum. The same problem (even to a larger extent) occurs with SQL or VM-type languages such as C#, Java, or Actionscript.

The ObjC instructions from Apple are the only ones I have seen so far that do a good job at explaining the runtime, and how OO constructs become procedural code. I am very impressed.

I have a first attempt at writing Mac OS X code here, a Cocoa front end to Unix queues. IPCS seems to not work with queues on Mac, but other than that the system calls seem to work quite well.

Friday, September 15, 2006

GoogleMaps v2

I finally rewrote the Maps application in a more objectified JavaScript. The source code is here and you can see it in action here. It seems that the Google Geocoder also does not recognize London, besides Hong Kong (actually, HK is sometimes recognized! what gives?) and Tokyo.

Flickr (FlickrMaps) uses it in a similar fashion.

Here is the UML Sequence Diagram of the interactions caused by this application:

Thursday, September 14, 2006

SQLite very easy to use. To use from C (assuming gcc is the compiler):

- #include sqlite3.h
- compile like this: gcc -lsqlite3 file.c
- you really only need 3 API functions, sqlite3_open, sqlite3_exec, sqlite3_close
- for sqlite3_exec, you need to provide a callback that takes the number of columns, the name of each column, and the value of each column; the callback is called by the library for each component of the resultset
- you can create a database using 'sqlite3 database_name.db' from a shell prompt.