On more than one occation when writing web code I found myself in the debugger in the middle of a request handler. The browser just sits there waiting for a response. I found the bug and restarted the handler before the browser time-outed. The browser recieved the response as if a bug never existed. Of course this only works if you can find and fix a bug in under 120 seconds :)
As a non-lisp user, this {easy-debug -> fix -> resume program} appears to be extremely useful, and something that only lisp offers.<p>e.g. wading through clojure stack traces seems very primitive in comparison.<p>How important is it in practice? Can/could other languages do this?<p>As an outsider looking at new (to me) languages, it's hard to judge what the pros and cons of a language are - especially the cons - e.g. several years ago, when looking at clojure, it took a lot of searching before I concluded that clojure did <i>not</i> have this feature (maybe that has changed now?). Meanwhile the 'learn language x' books always seem to focus only on syntax, rather than workflow.