## 1.4 Should you be using SWI-Prolog?

There are a number of reasons why you better choose a commercial Prolog system, or another academic product:

- SWI-Prolog is not supported
  Although I usually fix bugs shortly after a bug report arrives, I cannot promise anything. Now that the sources are provided, you can always dig into them yourself.
- Memory requirements and performance are your first concerns
  A number of commercial compilers are more keen on memory and performance than SWI-Prolog. I do not wish to sacrifice some of the nice features of the system, nor its portability to compete on raw performance.
- You need features not offered by SWI-Prolog
  In this case you may wish to give me suggestions for extensions. If you have great plans, please contact me (you might have to implement them yourself however).

On the other hand, SWI-Prolog offers some nice facilities:

- Nice environment
  This includes `Do What I Mean', automatic completion of atom names, history mechanism and a tracer that operates on single key-strokes. Interfaces to some standard editors are provided (and can be extended), as well as a facility to maintain programs (see make/0).
- Very fast compiler
  Even very large applications can be loaded in seconds on most machines. If this is not enough, there is a Quick Load Format that is slightly more compact and loading is almost always I/O bound.
- Transparent compiled code
  SWI-Prolog compiled code can be treated just as interpreted code: you can list it, trace it, etc. This implies you do not have to decide beforehand whether a module should be loaded for debugging or not. Also, performance is much better than the performance of most interpreters.
- Profiling
  SWI-Prolog offers tools for performance analysis, which can be very useful to optimise programs. Unless you are very familiar with Prolog and Prolog performance considerations this might be more helpful than a better compiler without these facilities.
- Flexibility
  SWI-Prolog can easily be integrated with C, supporting non-determinism in Prolog calling C as well as C calling Prolog (see section 9). It can also be embedded embedded in external programs (see section 9.5). System predicates can be redefined locally to provide compatibility with other Prolog systems.
- Integration with XPCE
  SWI-Prolog offers a tight integration to the Object Oriented Package for User Interface Development, called XPCE Anjewierden & Wielemaker, 1989. XPCE allows you to implement graphical user interfaces that are source-code compatible over Unix/X11, Win32 (Windows 95/98/ME and NT/2000/XP) and MacOS X (darwin).