The scoop: Scheme and Janet are great, but the author wants a more standalone language. What makes the difference is the breakloop, a full-blown REPL that opens when an error in a program occurs. Not a stacktrace, not a debugger; just build from the point where it's currently broken.

This sounds so amazing, why is Common Lisp not the most popular language out there? (asking as someone who almost never writes code)

Eventually you need to work with other people, and using a common time-shared or multi user session is unlikely. Now consider that lisp images generally can't be easily diff'd or merged.

And with that the edit-and-continue paradigm loses much of its value. If you have to commit changes to a shared source file anyhow then you'll be not much worse off with debugging a core dump.

People say this a lot, but they fail to take into account that you can debug your server live as it continues to handle normal traffic. Even if you don’t deploy changes via the REPL, merely debugging the problem in a REPL without restarting anything is a huge win.

Lots of languages that are not lisp have this ability.

examples please, because so far i have only seen this from common lisp and smalltalk. there is also pike where i can reload classes or objects at runtime, thus avoiding a full restart, but it's not as closely integrated as in smalltalk and you actually have to build your app in a way that allows you to do that.

Java supports live debugging and profiling.

But that’s not the same thing at all. If you’re debugging an exception in Java, you cannot continue execution as if the exception had not been thrown at all. With Common Lisp’s condition system you can.

https://www.jetbrains.com/help/idea/altering-the-program-s-e...