I don't know about general-purpose, but I've seen Prolog implementations for specific logic problems. Most recently, chalk [1], a Prolog interpreter designed to

I don't know about general-purpose, but I've seen Prolog implementations for specific logic problems. Most recently, chalk [1], a Prolog interpreter designed to be used in the Rust compiler's trait system. So I wouldn't say it's not popular, but the areas it's used in are probably not what most programmers deal with every day. [1]: https://github.com/nikomatsakis/chalk https://github.com/nikomatsakis/chalk