| Simon Peyton-Jones asks for programs that are broken by the proposed
| change. Here is a nearly real world one:
You may not like this but this should work:
Instead of
| t1 = runST (trav f [1..10] (1,52) >>= \ (s::STRef s (Set Int)) -> seen
s)
try
t1 = runST ( (trav f [1..10] (1,52) >>= \ s -> seen s)
:: forall s. ST s [Int] )
or, equivalently
t1 = runST run_it
where
run_it :: forall s. ST s Int
run_it = trav f [1..10] (1,52) >>= \s -> seen s
What's interesting about this example is that you aren't trying to bind
the type variable 's'. You'd be quite happy to write
\ (s :: STRef _ (Set Int)) -> seen s
Note the wildcard "_". Arguably, one could loosen the rules in this
case. This is an avenue that I have seen suggested before, but which I
have, for one, not yet explored. Maybe others have better ideas.
Simon
_______________________________________________
Glasgow-haskell-users mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
