On Wed, 2009-03-25 at 22:32 +0100, Henning Thielemann wrote:
On Wed, 25 Mar 2009, Jonathan Cast wrote:
On Wed, 2009-03-25 at 07:39 -0400, Xiao-Yong Jin wrote:
Could you elaborate more about why this kind of breakage wouldn't happen if 'try' is used in an IO monad as intended?
It would. But it would happen in IO, which is allowed to be non-deterministic. Pure Haskell is not allowed to be non-deterministic.
In my opinion, 'try' catching 'error's is still a hack, since 'error's aka bottom mean programming error. Thus catching them is debugging, bug hiding or something worse, but not exception handling.
100% agreed. The nice thing about the extensible exceptions is that you *can* decline to handle ErrorCall `exceptions'; but errors caught by try should be viewed analogously to signals or asynchronous exceptions. The RTS sometimes detects a bug and (sometimes!) stops execution with an exception; the user sometimes detects the bug and (sometimes!) stops execution with SIGINT. The most you can do is try to limit the amount of secondary damage and give the programmer the best clue where to start hunting. jcc