> > I don't know how to achieve the same goal with > > atomicModifyIORef. > > I do. To modify ioRef1 and ioRef2 "simultaneously", write > > atomicModifyIORef ioRef1 (\ contents1 -> unsafePerformIO > ioRef2 (\ contents2 -> blah blah)) > > The actual modification will take place when the result or > contents of ioRef1 or ioRef2 get evaluated.
I don't understand how this works. Unless I'm missing something, you'll see the contents of ioRef1 at the point at which the first atomicModifyIORef takes place, but the contents of ioRef2 from the time at which the unsafePerformIO is evaluated, which is some unspecified time later. Also another modification might come along before the first unsafePerformIO is evaluated, and it might see the "new" value of ioRef1 but the old value of ioRef2, if it doesn't evaluate the value of ioRef1 early enough. Nevertheless, I believe that the addition of atomicModifyIORef will let us write System.Random and Data.Dynamic in a safe way - both libraries have only a single global IORef to worry about. Cheers, Simon _______________________________________________ FFI mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/ffi