" they said that for those who use Prolog in production it is a real competitive advantage that they don't want to announce to the world;"
with due respect to prolog (which is a mindbending language), the proponents of every niche language say the same thing. "it is so powerful that users don't talk about it and that is why you don't hear about it"
I've heard many variants of this with respect to Forth, for example.
The reality is that devs can't stop talking about the languages, tools, and frameworks they use.
The simpler explanation is that next to no one actually uses prolog in productions, because it is, well, a niche language (which doesn't take away from its coolness)
Few people use it overall, yes. That doesn't mean it's not a differentiator in some areas.
You can often find a Prolog system behind complex scheduling and resource planning systems for example. It's no longer pure Prolog nowadays, you also have constraint logic programming and other solvers hooked in (see my other comment on ECLiPSe CLP, http://eclipseclp.org/) but Prolog is still often the host language. The ECLiPSe web page has for example a reference on Opel, the car maker, optimizing its supply chain with it. Sicstus (https://sicstus.sics.se/) is also present in this space.
Lisp ain't no "secret weapon" anymore. Clojure has restored historical awesomeness of Lisp. It's been rated as the most paid PL in most popular dev surveys of the past two-three years. Companies like Apple, Cisco, Amazon (even NASA) are using Clojure today in production.
"COBOL has historically been very secretive and low key. Its domain of use being very secretive and low key. COBOL programmers rarely work on systems that would allow for open internet chat regarding details, let alone existence. It is a tribute to the professionalism of these programmers that most people rarely, if ever, hear the name COBOL, a programming language with billions of lines of source code compiled and in production around the world over half a century." -- GnuCOBOL FAQ
with due respect to prolog (which is a mindbending language), the proponents of every niche language say the same thing. "it is so powerful that users don't talk about it and that is why you don't hear about it"
I've heard many variants of this with respect to Forth, for example.
The reality is that devs can't stop talking about the languages, tools, and frameworks they use.
The simpler explanation is that next to no one actually uses prolog in productions, because it is, well, a niche language (which doesn't take away from its coolness)
Color me skeptical about "secret weapons".