[stray]

I've never had to change my mind about Lisp -- but to me, Common Lisp's condition system kicks the crap out of every other language because it allows you to handle conditions without unwinding the stack.

And whenever you get dropped into the debugger, you can edit and reevaluate the broken code or values or whatever -- and then continue on with the task.

In other words, you can begin a task with imperfect code -- and refine it as you go along -- figuring out how to handle corner cases as you go. All without starting the task over from the beginning.

I know of only one other language that allows you to explore a problem space like that.

Besides, the parentheses make the code less jagged looking and jagged looking code imo, is more tiring to look at. Lisp is simply prettier.

[muraiki]

Smalltalk also drops you into a debugger on an error, letting you inspect the state of the system, correct your code, and resume. Check out Pharo Smalltalk.

[stray]

TIL.

I have edited my comment to account for smalltalk.

[TeMPOraL]

Smalltalk probably supports this as well, but what's cool about Common Lisp's condition system is that it doesn't depend on user interaction or debugger to work. Conditions let you separate the code making the decision about how to handle an error from actual error handling. The decision doesn't have to involve interactive debugger, you can have your code making the choice about which restart (unit of error handling code) to invoke. The common use case is that you install various restarts as you go down the call stack; then, when an exception happens, control goes up the stack until appropriate decision code, which selects restart, and control goes back down the call stack to the selected restart block.

It's an incredibly flexible system that makes exception handling much more useful.