Interestingly, IBM Watson uses Prolog. [1]
[1] https://www.cs.nmsu.edu/ALP/2011/03/natural-language-process...
I love Prolog and hope to spend more time with it some day. But, the step from Novice to Intermediate is steep.
MS Windows (network code) contains a Prolog with C-style-syntax.
Can you tell me details?
What's your solution?
The first thing is to use a different parsing strategy. For instance, the Earley parser [1] used to be a typical example of (advanced ish) Prolog and wikipedia says that it performs particularly well with left-recursive languages.
The disadvantage of course is that you're giving up the simplicity of having a built-in grammar-and-parser capability in your language. But in some cases that's probably a very small price to pay.
The other thing you can do, which is in a sense the exact opposite of changing parsers, is to eliminate the possibility of left-recursion from your DCGs by choosing a grammar formalism that precludes it.
It boils down to keeping all your rules looking like this:
P --> [a₁, a₂, ..., aₙ], A₁, A₂, .... Aₘ.
In other words, expand every nonterminal first to one or more terminals, then any mix of terminals and nonterminals. That way you'll always accept a terminal before expanding a nonterminal and there's no chance of left-recursion.
You can write a short syntax checker to enforce this rule in a post-processing step, or just do it by hand.
You can be a little bit more rigorous and stick to more strict forms, particularly right-regular grammars, or Greibach Normal Form [2], if your grammars are context-free.
Right regular grammars allow a single nonterminal on the right-hand side:
A --> [a], B.
P --> [a], A₁, A₂, .... Aₙ.
___________
Every time I hack in Prolog I always feel like I'm living the idea that I "tell the computer what to do not how to do it". It's a shame that more folks don't use it.