On 28 Mar 2008, at 10:59 pm, Benjamin L. Russell wrote:
The commercial SICStus Prolog is also substantially more expensive (see http://www.sics.se/isl/sicstuswww/site/index.html), at 153 euros for a Personal License (see http://www.sics.se/isl/sicstuswww/site/order4.html). Prices for Academic, Single-User Commercial, and Multi-User Commercial licenses are even more expensive, at 1560, 1980, and 7800 euros, respectively. An Evaluation License is only valid for 30 days.
Not all students and researchers can afford a Personal License.
Let me contrast SICStus Prolog with GHC. I *have* a personal copy of SICStus on my SunBlade 100/Solaris 2.10 system which installed absolutely trouble free. I *did* have a copy of GHC, but trying to install GHC 6.4 took a great deal of my time and now I don't have a working GHC any more. So for me, GHC is by far the more expensive: I've spent considerably more than 500 Euros of my time and got nothing for it. Much though I admire Jan, I've also had such a lot of trouble installing SWI Prolog on various machines that SICStus was *really* cheaper than the "free" Prolog after all. I do wish people would remember that not all the world is Linux. 153 Euros (why did the Europeans name their currency after the Common Wallaroo?) is NZD 303 or about the price of two textbooks. (Three copies of Bird's introduction to functional programming would do it, if they shipped free.) You're telling me that *researchers* can't afford the price of a couple of books? The academic licence isn't that unreasonable. 1560 Euros is NZD 3091, which is about one month of a TA's pay. Another 880 Euros gives you the right to give your students free binaries, however many students you have, year after year after year.
Can you recommend an alternative, fast Prolog development system under a free licensing agreement, such as GPL/GLPL?
There is, after all, GNU Prolog. The last time I saw any benchmarks, it was substantially faster than SWI, while not quite as good as SICStus. See http://gprolog.inria.fr/ or http://www.gprolog.org/ For what it's worth, GNU Prolog's developers *do* realise that not all the world's linux.