Full Metal Jacket is general-purpose. Doing general-purpose programming in it does, however, has required me to think very differently. At present, it's still easier for me to program in Lisp, but that's mostly down to being a very experienced Lisp programmer and a rookie FMJ programmer. Initial difficulties are inevitable when you learn a new programming language different from the languages you already know. I had similar issues with Prolog but mastered that.

Different general-purpose languages are better adapted to different programming tasks, however, and Full Metal Jacket may in time find its niche. I wouldn't write a neural network in Prolog, or an expert system in C, for example.