zaxis <z_a...@163.com> writes: >>>value <- readIORef aaa >>>writeIORef aaa (f value)
> then aaa will *point to* a new value. Exactly. That's what IORefs are, references pointing to contents that can be changed in the IO monad. > The original value will be Garbage Collected, right ? Yes, unless something else is holding on to it. > Is [(1,1),(2,2),(3,3)] been regarded as a hash? It's a list of pairs. You can treat it as an association list using e.g. 'lookup' from Data.List, if that's what you mean. > If not, what is the best way to change it to [(1,1),(2,2222),(3,3)] in > function `f` ? Not sure if there's anything in Data.List, but you could do something like: f xs = (2,2222) : filter ((/=2) . fst) xs -k -- If I haven't seen further, it is by standing in the footprints of giants _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
