> No, user-defined functions won't make Meson Turing-complete as long as recursion is not allowed. Turing-completeness is, itself, often a red herring. What it

> No, user-defined functions won't make Meson Turing-complete as long as recursion is not allowed. Turing-completeness is, itself, often a red herring. What it alludes to is the difficulty in predicting what a program would do because, in the general case, it is impossible to tell what behaviour a program in a Turing-complete language would exhibit for a particular input short of observing what it actually does. But even languages that are not Turing-complete often fall far beyond what is practically predictable. While theoretically decidable, predicting what a program written in a language with nothing but boolean variables and loops of no more than two iterations, or, alternatively, functions of boolean parameters even without recursion, is PSPACE-complete (as such a language can easily encode TQBF [1]). I.e. predicting how such a program would behave is computationally intractable, since it grows exponentially with the size of the program. Programs in such a language would also fall outside the capabilities of heuristic methods, such as SAT solvers, to tackle (SAT is merely NP-hard compared to the strictly harder PSPACE-hard TQBF). So if your language has variables and loops (even limited to two iterations), or variables and functions (even without recursion) -- it's intractable, even though it's not Turing-complete. I don't know whether this particular language qualifies or not. [1]: https://en.wikipedia.org/wiki/True_quantified_Boolean_formula https://en.wikipedia.org/wiki/True_quantified_Boolean_formul...