Yes, although they're replacements more than extensions. Stdlib is OCaml's builtin standard library, Base is Jane Street's lightweight replacement of Stdlib (al

Yes, although they're replacements more than extensions. Stdlib is OCaml's builtin standard library, Base is Jane Street's lightweight replacement of Stdlib (although the most basic types are compatible), and Core is Jane Street's full standard library extending Base. There's nothing inherently wrong with them, aside from their API being unstable, but they're an opinionated wedge in an ecosystem already lacking the cohesion of newer languages.