Hi Rich, I am very interested in your view of the world - why are 'checked' exceptions evil?
Thanks -Ralf On Thu, Dec 11, 2008 at 2:08 PM, Rich Hickey <richhic...@gmail.com> wrote: > > > > On Dec 10, 10:52 pm, "Stephen C. Gilardi" <squee...@mac.com> wrote: > > On Dec 10, 2008, at 4:38 AM, Ralf Bensmann wrote: > > > > > Being a Java trainer for a long time, we talk with students about > > > the "handle-or-declare rule" in Java and the two types of > > > exceptions: "checked" (declared) and "unchecked" (runtime). So I > > > prefer using a RuntimeException because no exception was specified. > > > > I'm inclined to accept the recommendation to make RuntimeException the > > default. I see that Clojure's Java source code uses both. It seems to > > me that within Clojure, the distinction doesn't matter, but in the > > case of Java interop, RuntimeExceptions would be more in keeping with > > what Clojure's "never declare them" philosophy. > > > > Does anyone have any more advice on this? > > > > Clojure doesn't have 'checked' exceptions. They are a bad idea, and a > misfeature of Java, bad enough with interfaces but completely > incompatible with closures. As a result of the flawed logic that has > grown up around this misfeature, in Java you might choose between > checked and non-checked based on whether you thought a caller could do > anything about it - if not, use unchecked, thus making your method one > that didn't require explicit handling. > > Given that there are no 'checked' exceptions in Clojure, the > distinction is moot, except in the case of Java interop, where, at > least through the IFn interface, all Clojure calls declare Exception. > RuntimeException is a particularly dubious notion, a special exemption > granted to those exceptions the Java runtime might throw, created in > acknowledgment of the insufferable pain it would cause to use the > checked exception system for those. If it were a fixed set it would be > one thing - every caller could expect one of those (enumerated, > documented) exceptions, or a declared one. But RuntimeExceptions are > an open set - it's just plain goofy. > > Clojure's Java code throws explicit RuntimeExceptions only in those > places where the checked exception system precludes it from letting an > Exception flow out, and it pains me every time. > > I guess my recommendation is, if there is an existing exception type > (checked or unchecked) that roughly matches your problem, throw that, > else throw Exception. In this case, perhaps the default should be > IllegalArgumentException. > > Rich > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
