The best example of all is Prolog. It is always held up as the paradigmatic representative of logic programming, a rare language paradigm. But it doesn't need to be a language. It is really a collection of algorithms which should be a library in every language, together with a nice convention for expressing Prolog things in that language's syntax.
(My comment is slightly off-topic to the article but on-topic to the title.)
(My comment is slightly off-topic to the article but on-topic to the title.)