Gilad Bracha asks Will Continuations Continue? in an excellent essay about whether the JVM needs continuations. Personally I have never found them idiomatic so I have no quarrel with Gilad’s reluctance, but I entirely disagree with the line of argument he uses to back it up. He points out that Web frameworks like Seaside make excellent use of continuations, but argues that that’s a red herring because the current style of Web-human interaction is a temporary anomaly and “the future of Web apps will be different”, with AJAX signposting the way. This notion, that the Web GUI is insufficiently interactive and we need something richer, is widely held among developers and almost never among actual users of computers, and it’s entirely wrong. I can remember when people were forced to use compiled Windows and X11 applications, and most of them were extremely bad because it’s really hard to design a good interactive UI; when the Web came along, more or less everyone abandoned those UIs in favor of the Web, almost instantly and with shrieks of glee. Yes, Web UIs are drastically constrained, offer a paucity of controls, and enforce a brutally linear control flow; and these are good things. I remember, in the early days, people saying “Once you know how to use one Windows app, you know how to use them all”. Ha ha ha. But you know what? Once you know how to use a browser, you are well on the way to being able to use most Web apps. The best AJAX apps are still very Web-like (as in, the Back button always works); but they’re faster and more responsive and nicer to look at. The worst AJAX apps are like bad Nineties VB. Having said all that, I suspect that Gilad’s right about continuations. [Update: More good stuff on the subject from Don Box and (especially) David Megginson. Plus a few remarks, in a superior tone, along the lines of “That silly man, can’t he see that users really want more complex user interfaces?” All, of course, from developers.] [Further: Some pro-complex-interface remarks that are actually coherent from Simon Brocklehurst (but Simon, a good browser should pre-fill forms for you and get it right almost all the time; Safari does). And there’s more solid thinking in HREF Considered Harmful; I know who writes it but he seems to be trying to hide his identity, hmm.] [Hrumph. Curtis Poe says I’m a Sapir-Whorf victim, I don’t feel the need for continuations because I’ve spent too many years using pathetic, impoverished languages like C and Java. Well, OK then; I promise to find a way to squeeze ’em into my Ruby-based comment system.]
