I do all my Haskell development in a repl driven way. It's even better than Python's repl due to the way it loads modules and allows reloading quickly and autom

I do all my Haskell development in a repl driven way. It's even better than Python's repl due to the way it loads modules and allows reloading quickly and automatically checks the type signatures. Having the entire application loaded into your repl is even more powerful. I did it once in PHP using psych and was able to make use of any controller and try parts of it out. The main thing that is necessary is the ability of the REPL to either drive change to the code, or react to changes on file (the former is temporal, the latter is more permanent) and perform the necessary incremental computation to become eventually consistent.