Often developing using the repl consists of a lot of copy pasting back and forth between then editor and the repl. Moving the repl into the editor makes this even less painful, but I would argue that in order to fully embrace a repl one has to have something like lisp, or a very good editor (that I havn’t seen yet). In lisp it’s very easy to take parts of a function and evaluation only that part simply by finding the right parenthesis and evaluation that. Using Emacs and SLIME it’s a simple two-key-gesture.

But one can take it one step further. Why not simply start your program as a repl, instead of adding a repl to your program. That way also the running state of the program can be determined. But in order for that to work, one has to be able to redefine functions without stopping the program. Clojure allows that, and it’s the key that makes it all work.

Programming in clojure is a process of organically growing your program in a bottom-up fashion where the running state of the program allows one to inspect, debug and fix programs all without shutting it down.

The best way to do this is to start up a repl in a seperate process and then to connect to that process, that way one can always disconnect and reconnect again when the need arises.

• Database has at least two things that makes it less than ideal for agile development. First one being types, especially if the types propagate out into the application code (*cough* Microsoft). The second being based on a schema, which means that one has to make all the choices up front.
• Databases are really built for a single machine, and even though all the big database vendors has replication support, it still seems like a bad solution if one really wants scalability. There are a lot better ways of doing scalability now a days (a distributed hash tables comes to mind).
• Databases are meant to be standardized, but in reality they are not. They all have different syntax to do common things.
• It has been said that when you build a DSL, then sooner or later it will turn into a (bad) full-fledged programming language. What if instead the data was simply part of the program and you could manipulate it as you are used to? Functional languages makes this much easier and possible. Especially a programming language that is built with concurrency in mind.