Hello Hugh, Sunday, July 1, 2007, 8:56:05 PM, you wrote:
Genuine question: please could you tell me what are the truly powerful features of Haskell?
Anyway, getting back to my question, there's a whole slew of articles around saying that no-one uses Haskell because they're too stupid. That's certainly an argument, but it possibly lacks a certain objectivity ;-)
i agree with it. haskell represents new programming paradigm and most programmers are unable to learn it without help of college in other words, there is not yet enough learning infrastructure for FP languages. the same situation was in 80s for OOP languages. this means that learning FP require much more work, or, spending the same time, one will learn FP much worse than OOP
So... what do you see as the "Killer Advantages" that make Haskell stand out from the pack?
i've written 8kloc "real world" program in haskell and can say what was killer features for me: - natural data structures and easiness of defining algorithms - rich set of list operations - easiness of use of higher-level functions - type inference (dropping almost all declarations) - strong type checking detects many errors just at compile time - non-updateable data simplifies algorithms development for concurrent programming: - it's easy to split algorithm to several parts that are run concurrently and exchange data - channels allows to organize data streams (like Unix pipes) between threads, non-updatability of data significantly simplifies usage of these data - MVar allows to implement shared updateable variables which automatically locks on their use shortly said, non-updatability of data significantly simplifies both usual programming and concurrency, especially later. you can do the same with C# it's an example how i use concurrency for data archiving and compression: - first thread scans disk and finds files to compress. it sends filenames to its output stream - second thread reads contents of these files and sends memory buffers filled with data read to its output stream. it also runs background decompression stream which decompress data from old archive - third thread runs one or several C streams which compress its input buffers and sends buffers with compressed data to output stream. it may be several threads that do it, making a pipe - fourth thread writes compressed data to output archive all four threads are started by line runP$ scanning |> reading |> compression |> writing where each thread represented by a function which has additional argument for exchanging data with previous and next thread in list: reading pipe = do nextFile <- readP pipe .... writeP pipe buffer running additional background thread and exchanging information with it is also trivial: decompressor <- runAsyncP decompressor writeP decompressor request buffer <- readP decompressor you can see module which implements this as Process.hs from http://www.haskell.org/bz/FreeArc-sources.tar.gz although it's actually only a thin layer around forkIO/Chan/MVar features you can do the same in C# although i guess that syntax overhead will be a bit more and allocating a lot of small non-updateable values may be less efficient because its GC isn't aimed to such usage btw, are you read Hoar's book "Communicating Sequential Processes"? i think that his model is very FPish and reading his book should allow to switch your look at concurrency in right direction -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com