On 11 April 2006 13:35, John Meacham wrote:

On Tue, Apr 11, 2006 at 01:24:07PM +0100, Simon Marlow wrote:

...

Attached is another variant of the extensible exceptions idea, it improves on the previous designs in a couple of ways: there's only one catch & throw, regardless of what type you're throwing or catching. There is an extensible hierarchy of exceptions, and you can catch and re-throw subclasses of exceptions.

I made the catch and throw separate so the decision as to whether to include imprecice exceptions and extensible extensions can be made independently.

that and

throw x /= ioError x

ioError x >> return () -> IO _|_ (only _|_ when IO action executed) throw x >> return () -> _|_

ioError x `seq` () -> () throw x `seq` () -> _|_

yes, when I say "one throw" I was referring to the argument type, not the return type. We should still have ioError - although it would probably be better named throwIO: http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Excep tion.html#v%3AthrowIO (the docs for throwIO also mention the strictness property you described above) Cheers, Simon