Thats my point is that the REPL case of using Emacs to run and evaluate your code is almost hardly different than letting an IDE run your unit test. With Java this evident because the IDE compiles incrementally and the debugger can hot code swap.

The power of the REPL should not be the evaluation portion but the input or the print otherwise you can just about do any quick evaluation for any language that compiles reasonable fast.

Other than Jupyter Notebook the ones you mention don't really have any amazing output other than pretty print. To the authors point it also helps for the pretty print if the language is homoiconic.

As for input there is even fewer that have Excel like rapid response feedback. See Bret Victor on this. There was a recent company presented here on HN called Luna [1] who have a very cool REPL. Now that is where I think REPLs should be.

> P.S. I didn't get your point about python having nominal types, duck typing seems closer to structural typing to me and mypy seems to support both, but maybe I misunderstood you. Thanks for the thought provoking discussion though :)

For the most part you need to name functions in Python (lambda support I believe is even on the way out but I can't recall the status). In fact other than I guess tuples you need to name everything in Python.

But to your point structural typing means less in a duck typing environment particularly one with really late dispatch.

[1]: https://news.ycombinator.com/item?id=14612680