It seems to work pretty well for the things I've used it for. There are some problems that are better served by an imperative solution with in-place mutable array operations and so on, but the ST monad works pretty well for that.
I think that's one of the things that tends to take a long time to learn: Haskell imposes a lot of limitations up front on what you can do. The rules (and in particular the barriers between pure and impure code) aren't quite as rigid at they seem. There are ways to work around them without actually breaking any of the soundness rules.
(To be fair, there is one well-known foot gun, which is that if you lazily read from a file and close the file, the consumer of the file's contents will often get truncated results. So don't do that. Maybe it's been fixed by now, or that API's been deprecated? I haven't really kept up on current events in the Haskell world.)
> (To be fair, there is one well-known foot gun, which is that if you lazily read from a file and close the file, the consumer of the file's contents will often get truncated results. So don't do that. Maybe it's been fixed by now, or that API's been deprecated? I haven't really kept up on current events in the Haskell world.)
I think the API is still there, but lazy IO is so heavily discouraged that no one is using it. It's not relevant anymore and considered a mistake.
I think that's one of the things that tends to take a long time to learn: Haskell imposes a lot of limitations up front on what you can do. The rules (and in particular the barriers between pure and impure code) aren't quite as rigid at they seem. There are ways to work around them without actually breaking any of the soundness rules.
(To be fair, there is one well-known foot gun, which is that if you lazily read from a file and close the file, the consumer of the file's contents will often get truncated results. So don't do that. Maybe it's been fixed by now, or that API's been deprecated? I haven't really kept up on current events in the Haskell world.)