libxml++ vs xerces C++

When I was reading "API: Design Matters" I recalled one example of good API vs bad API. Actually my example is more about good API documentation vs bad API documentation but I suspect there is a correlation between these two things. It is definitely hard to write good documentation if your API sucks.

So my story is that I had a task to read XML data in C++ application. XML data was small and performance of this part of the application was not critical so it looked like the simplest way to read this data was to load DOM tree for XML document and just use DOM API and maybe couple simple XPath queries. It was the first time I needed to do this in C++; I had no previous experience with any XML C++ libraries. So, I do google search (or maybe it was apt-cache search - I don't remember) and the first thing I find is xerces C++. Quote from project's website:

Xerces-C++ makes it easy to give your application the ability to read and write XML data.

Sounds good, just what I need. So I dig documentation and find it to be completely unhelpful as it is just Doxygen autogenerated undocumentation. Fine, I can read code, let's check sample code then. I open sample code and I find that the shortest example how to parse XML into DOM tree and how to access data in the tree (DOMCount) consists of two files which are more then 600 lines long in total. Huh? I don't want to read 15 pages of code just to learn how to do two simple actions: parse XML into DOM and get data from DOM. Other examples are even more bad. Several files, several classes just to read and print freaking XML (DOMPrint). You've got to be kidding me. It cannot be that hard.

I don't really want to waste hours to learn API I'm unlikely to use ever again. After all I don't write much C++ code and I definitely don't write much C++ code that needs XML. So time to search further. Next hit is libxml++. It is C++ wrapper over popular C XML library libxml. This time there is actually some documentation that does try to explain how to use the library. And this documentation contains an example which while being just about 150 lines manages to demonstrate most of library's DOM API.

End result: I finish my code to read my XML data in next 30 minutes using libxml++. It is simple, short and it works.

So what's wrong with xerces C++? There is no introduction level documentation at all. Examples look too complex for the problem they are supposed to show solution for. And the reason for this is that API is just bad: it requires writing unnecessary complex client code.

Update: boris corrected me about lack of introduction level documentation in a comment to this blog post. Turned out I missed it. As a weak excuse I'll blame bad navigation on the project's site :)

boost::thread and boost::mutex tutorial

For most Boost's libraries its documentation requires you to read everything from the start to the end before you can write any code. Compare that with most of CPAN modules where usually you can start using CPAN module after quickly scanning synopsis and maybe description parts of it's POD documentation. POD documentation as a rule has good examples right on top of the page. Boost's documentation usually doesn't.

So I was looking for basic usage examples for boost::thread and boost::mutex classes and initially I couldn't find any because I was using wrong search keywords. In the end I figured out how to use boost::thread and boost::mutex classes in my application hard way by reading Boost documentation without relying on any examples. But afterwards I did find a very good article on this topic with many simple examples: The Boost.Threads Library on Dr.Dobb's. So I'm posting this link here for google. It is in top 10 hits for some relevant keywords but it is not for others (for example for boost thread mutex tutorial) and this is why I missed it initially. If my blog post helps any Boost.Threads newbie to get started then I would consider time spent writing this post to be not wasted.