[kscarlet]

I think the Common Lisp ecosystem sets a good example of how a dozen of implementations move ahead together. Implementations experiment with extensions, the really useful ones get implemented multiple times, and some portability library emerges as de-facto standard if it's good enough. You can watch the result in https://portability.cl/, the language is evolving like never before even if the standard committee has dissolved nearly 40 years ago!

[eska]

Isn’t this only possible in lisp due to the strong foundations of meta programming allowing the implementation of language features as user libraries?

[kscarlet]

Not directly. Every "extensions" listed above cannot be implemented as user libraries, that's why these back and forth process between implementation extensions and portability user libraries need to happen to reach a de-facto standard. Otherwise the user libraries become de-facto standard themselves, like ASDF the build system, Trivia the pattern matcher...

But I think the power dynamics is crucial. In the Lisp ecosystem the users have great power, (and there are dozens of implementations,) so it's not like one or two implementation decides what everyone is gonna use and everyone just lives with it.

[cestith]

I don’t know that it’s impossible without that. It’s certainly easier with it.