It's a pattern match error, implemented by throwing an asynchronous exception. The idea being, that we only have one mechanism (well, an synchronous exceptions, thrown via throwIO).
Yes, I know that there's a difference between "error" and "exception", but I would argue that which is which depends on the program. For example, for most programs a pattern match error is a fatal condition, there's no sane recovery from it. OTOH, in a program like GHCi, a pattern match error in an executed statement is an exceptional condition, which we want to catch, so it doesn't kill GHCi. 2008/11/22 Henning Thielemann <[EMAIL PROTECTED]>: > > On Sat, 22 Nov 2008, Thomas Schilling wrote: > >> Be careful, though. This only works if there's a single constructor >> for your exception type. If there are multiple, you should write it >> like this: >> >> thing_to_try `catch` \(e :: MyErrorType) -> case e of MyError1 _ -> >> ..; MyError2 _ -> ... >> >> If you write `catch` (MyError1 ...) and a MyError2 is thrown, you will >> get a pattern match error exception. > > A "pattern match exception" or "pattern match error"? I mean, not handling a > certain pattern is a programming error not an exceptional condition at > runtime. Thus there is no need to throw a "pattern match exception" which is > catched and handled somewhere else. > > -- Push the envelope. Watch it bend. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
