I tried to explain it in the adjacent thread https://news.ycombinator.com/item?id=22381081 https://news.ycombinator.com/item?id=22381081 But I think one has to

I tried to explain it in the adjacent thread https://news.ycombinator.com/item?id=22381081 https://news.ycombinator.com/item?id=22381081 But I think one has to experience it, to understand what makes languages like Lisp and Smalltalk so special, what is so unique about REPL driven workflow that even Python's so much praised Jupyter can't give you that satisfactory feeling. It's really nice to be able to run anything - from the smallest unit in your program, as well as the whole program and see the immediate feedback. For example: You can evaluate SQL DSL constructs and see what SQL query they compose into, and you can run that query and see the results (all without ever having to write a single line of actual SQL); or you can connect to the browser and change elements of the DOM (without writing a single line of html, css or js). You can take a complex piece of code that generates a .csv, and then analyze that csv on the fly, changing columns and rows on the go, without even saving and having to wait for the compiler to pass the checks. You can compose music and data visualizations, and etc.