3 ms·
> Artificially pure packages. There are some packages that link to C libraries, but (forcefully) provide a pure interface. (Or in other words: purity is just co
by anothermachine 15y ago
> Artificially pure packages. There are some packages that link to C libraries, but (forcefully) provide a pure interface. (Or in other words: purity is just convention)
Explain? What would the alternative be?
> Using functions with worse time or space complexity, to maintain purity.
This seems like the opposite of your previous complaint.
> For a lot of code you end up using monads plus 'do' notation, making your programs look practically imperative, but an oddball variation of it.
This seems to be a "psychological problem" with Haskell: the idea that because Haskell supports declarative, it's not OK to be imperative. It makes beginners tear their hair out looking for 'do'-free solutions when they could just use 'do'. C.f., "Lambda: the Ultimate Imperative" (and the rest of that series of LtU papers) http://dspace.mit.edu/handle/1721.1/5790 http://dspace.mit.edu/handle/1721.1/5790
- danieldk 15y agoExplain? What would the alternative be? Box the value that is the result of evaluation an expression that calls impure code in IO? This is what I'd expect for calling impure code in third-party libraries.
- jrockway 15y agoIf the library developer can prove that a C operation is pure, why shouldn't he tell Haskell about that?
- jrockway 15y agoAnd if you don't trust the developer, it's easy to fix his mistake: unUnsafePerformIO :: a -> IO a unUnsafePerformIO = return
- ezyang 15y agoSorry, that doesn't actually work. ezyang@ezyang:~$ cat Test.hs import System.IO.Unsafe unUnsafePerformIO = return main = do let a = unUnsafePerformIO (unsafePerformIO (putStrLn "boom")) a a ezyang@ezyang:~$ runghc Test.hs ezyang@ezyang:~$
- jrockway 15y agoYes, true. Patch the library if the annotation is wrong :)