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  • Problem with pattern matching in ocaml

    - by Antony
    I wrote the function used to decompose a Boolean function, the problem is that the compilation I get this : "Warning 5: this function application is partial, maybe some arguments are missing." How can I solve this problem? I've set wrong the patter matching or I can not run this operation with pattern matching The code is the following: let rec decomposition state_init state prec formula = match formula with And form -> (fun () -> let f1 = List.hd form in let f2 = And(List.tl form )in let new_state = Forms (state_init,f1) in decomposition state_init new_state state f1; decomposition state_init new_state state f2; Hashtbl.add graph new_state (("",false,state :: []) , []) ; let x = Hashtbl.find graph state in let succ = state :: snd x in let (desc,last,ptrs) = fst x in Hashtbl.replace graph state ( ("And-node",last,ptrs) , succ))

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  • Writing Java code in Matlab?

    - by scooziexp
    Hi, I'm trying to use the Java commands pw.println() and br.readLine() in Matlab because I have set up a socket (input_socket2) between Matlab and a command-line program I want to control using Java classes BufferedReader and PrintWriter. Before the following snippet of code, I implemented another socket that goes between 2 computers. This works great and I also know that the following snippet of code successfully opens up a communication line between Matlab and the other program. However, Matlab throws an error at pw.println('noop'). I think it has something to do with syntax, but I'm not sure how to write the command in Matlab syntax then: try input_socket2 = Socket(host2,port2); input_stream2 = input_socket2.getInputStream; d_input_stream2 = DataInputStream(input_stream2); br = BufferedReader(InputStreamReader(input_stream2)); pw = PrintWriter(input_socket2.getOutputStream,true); pw.println('noop') br.read end Any ideas?

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  • implementing type inference

    - by deepblue
    well I see some interesting discussions here about static vs. dynamic typing I generally prefer static typing, due to compile type checking, better documented code,etc. However I do agree that they do clutter up the code if done the way Java does it, for example. so Im about to start building a language of my own and type inference is one of the things that I want to implement, in a functional style language... I do understand that it is a big subject, and Im not trying to create something that has not been done before, just basic inferencing... any pointers on what to read up that will help me with this? preferably something more pragmatic/practical as oppose to more theoretical category theory/type theory texts. If there's a implementation discussion text out here, with data structures/algorithms, that would just be lovely much appreciated

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  • Why do people develop emotional attachments for programming languages?

    - by Andrew Heath
    Aside from people who actually developed the languages, I really don't get how someone can develop passion/attachment/perhaps even obsession for a programming language... yet not a day goes by that I don't see a programmer exhibiting this behavior on the internet. I understand how people can feel this way regarding spoken languages - but there's a whole boatload of culture, history, etc that come attached with them. By comparison, the "Python Culture" (as an example) is so small as to be wholly insignificant. Does everyone have a language they love? Am I the odd one out? The dirty polygamist? Are these people rational or silly?

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  • Career Path Choices (Education)

    - by sandy101
    I am in the final year of bca from md university. I am not sure with my career and very confused with the question of should I do MCA or MBA? Can any one help me on this question? I want to know the options available to me, and I also want to know the various colleges which provide MCA and what are the further prospects thereafter!

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  • How do "modern JVMs" differ from older JVMs?

    - by Lord Torgamus
    Here's a phrase that I heard a lot throughout high school and university computer science classes: "That's not an issue for modern JVMs." Usually this would come up in discussions about overall performance or optimization strategies. It was always treated as a kind of magical final answer, though, as if it makes issues no longer worth thinking about. And that just leads me to wonder: what are the differences between the prototypical "modern JVM" and older JVMs, really?

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  • Android HTTP Connection

    - by Ubersoldat
    Can anybody tell my why this doesn't work in the Android emulator? From the browser I have access and the server is internal. All I can think of is that I'm missing some configuration on my app so it can access the network layer. try { InetAddress server = Inet4Address.getByName("thehost"); //Doesn't work either //or InetAddress server2 = Inet4Address.getByAddress(new String("192.168.1.30").getBytes()); if(server.isReachable(5000)){ Log.d(TAG, "Ping!"); } Socket clientsocket = new Socket(server, 8080); } catch (UnknownHostException e) { Log.e(TAG, "Server Not Found"); } catch (IOException e) { Log.e(TAG, "Couldn't open socket"); } Throws an UnknownHostException Thanks

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  • Appending an element to a collection using LINQ

    - by SRKX
    I am trying to process some list with a functional approach in C#. The idea is that I have a collection of Tuple<T,double> and I want to change the Item 2 of some element T. The functional way to do so, as data is immutable, is to take the list, filter for all elements where the element is different from the one to change, and the append a new tuple with the new values. My problem is that I do not know how to append the element at the end. I would like to do: public List<Tuple<T,double>> Replace(List<Tuple<T,double>> collection, T term,double value) { return collection.Where(x=>!x.Item1.Equals(term)).Append(Tuple.Create(term,value)); } But there is no Append method. Is there something else?

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  • Right rotate of tree in Haskell: how is it work?

    - by Roman
    I don't know haskell syntax, but I know some FP concepts (like algebraic data types, pattern matching, higher-order functions ect). Can someone explain please, what does this code mean: data Tree ? = Leaf ? | Fork ? (Tree ?) (Tree ?) rotateR tree = case tree of Fork q (Fork p a b) c -> Fork p a (Fork q b c) As I understand, first line is something like Tree-type declaration (but I don't understand it exactly). Second line includes pattern matching (I don't understand as well why do we need to use pattern matching here). And third line does something absolutely unreadable for non-haskell developer. I've found definition of Fork as fork (f,g) x = (f x, g x) but I can't move further anymore.

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  • How do you manage tasks within your work?

    - by Michael
    Just wondering how you all manage your workload effectively when there's a lot of your plate? What do you do to break it down into bite-size chunks and how do you track progress of each task? Do you find TDD helps to focus your attention of getting areas of functionality complete before moving onto the next one? I quite often find myself getting a bit overwhelmed when I have an involving task on the go (even if it can be broken down into lots of small chunks), even though I know I'm more than capable of doing the work. We have a kind of agile approach Interested to hear how everyone manages things effectively.

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  • using object in multiple function

    - by nixon
    Hi. How can i use object from one function in another ? main() { private void button1_click { MyClass object = new MyClass(); object.blabla(); } private void button2_click { // how can i use object from button1_click ?? } }

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  • functional, bind1st and mem_fun

    - by Neil G
    Why won't this compile? #include <functional> #include <boost/function.hpp> class A { A() { typedef boost::function<void ()> FunctionCall; FunctionCall f = std::bind1st(std::mem_fun(&A::process), this); } void process() {} }; Errors: In file included from /opt/local/include/gcc44/c++/bits/stl_function.h:712, from /opt/local/include/gcc44/c++/functional:50, from a.cc:1: /opt/local/include/gcc44/c++/backward/binders.h: In instantiation of 'std::binder1st<std::mem_fun_t<void, A> >': a.cc:7: instantiated from here /opt/local/include/gcc44/c++/backward/binders.h:100: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:103: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:106: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:111: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:117: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h: In function 'std::binder1st<_Operation> std::bind1st(const _Operation&, const _Tp&) [with _Operation = std::mem_fun_t<void, A>, _Tp = A*]': a.cc:7: instantiated from here /opt/local/include/gcc44/c++/backward/binders.h:126: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' In file included from /opt/local/include/boost/function/detail/maybe_include.hpp:13, from /opt/local/include/boost/function/detail/function_iterate.hpp:14, from /opt/local/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:47, from /opt/local/include/boost/function.hpp:64, from a.cc:2: /opt/local/include/boost/function/function_template.hpp: In static member function 'static void boost::detail::function::void_function_obj_invoker0<FunctionObj, R>::invoke(boost::detail::function::function_buffer&) [with FunctionObj = std::binder1st<std::mem_fun_t<void, A> >, R = void]': /opt/local/include/boost/function/function_template.hpp:913: instantiated from 'void boost::function0<R>::assign_to(Functor) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' /opt/local/include/boost/function/function_template.hpp:722: instantiated from 'boost::function0<R>::function0(Functor, typename boost::enable_if_c<boost::type_traits::ice_not::value, int>::type) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' /opt/local/include/boost/function/function_template.hpp:1064: instantiated from 'boost::function<R()>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not::value, int>::type) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' a.cc:7: instantiated from here /opt/local/include/boost/function/function_template.hpp:153: error: no match for call to '(std::binder1st<std::mem_fun_t<void, A> >) ()'

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  • help, stuck with logic variable comparison loop, javascript

    - by Jamex
    I have an input text box for search of input, the id of the text box is: id="search". if a user enters 'cat' at first and hit search. In the function, I get the value 'cat' by using the syntax: var input = document.getElementById("search").value; After that, the user enter 'dog' in the search box and hit search using the same function. The function would assign 'dog' to the input variable. How would I compare the current value (dog) to the previously entered value (cat)? I have tried to assign the original input with a statement, something like var orig = input; but that would only overwrite the original input with the new input. What is the logical approach to this problem.

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  • Efficient algorithm to distribute work?

    - by Zwei Steinen
    It's a bit complicated to explain but here we go. We have problems like this (code is pseudo-code, and is only for illustrating the problem. Sorry it's in java. If you don't understand, I'd be glad to explain.). class Problem { final Set<Integer> allSectionIds = { 1,2,4,6,7,8,10 }; final Data data = //Some data } And a subproblem is: class SubProblem { final Set<Integer> targetedSectionIds; final Data data; SubProblem(Set<Integer> targetedSectionsIds, Data data){ this.targetedSectionIds = targetedSectionIds; this.data = data; } } Work will look like this, then. class Work implements Runnable { final Set<Section> subSections; final Data data; final Result result; Work(Set<Section> subSections, Data data) { this.sections = SubSections; this.data = data; } @Override public void run(){ for(Section section : subSections){ result.addUp(compute(data, section)); } } } Now we have instances of 'Worker', that have their own state sections I have. class Worker implements ExecutorService { final Map<Integer,Section> sectionsIHave; { sectionsIHave = {1:section1, 5:section5, 8:section8 }; } final ExecutorService executor = //some executor. @Override public void execute(SubProblem problem){ Set<Section> sectionsNeeded = fetchSections(problem.targetedSectionIds); super.execute(new Work(sectionsNeeded, problem.data); } } phew. So, we have a lot of Problems and Workers are constantly asking for more SubProblems. My task is to break up Problems into SubProblem and give it to them. The difficulty is however, that I have to later collect all the results for the SubProblems and merge (reduce) them into a Result for the whole Problem. This is however, costly, so I want to give the workers "chunks" that are as big as possible (has as many targetedSections as possible). It doesn't have to be perfect (mathematically as efficient as possible or something). I mean, I guess that it is impossible to have a perfect solution, because you can't predict how long each computation will take, etc.. But is there a good heuristic solution for this? Or maybe some resources I can read up before I go into designing? Any advice is highly appreciated!

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  • Can someone who understands C code help me understand this code?

    - by Benjamin
    INT GetTree (HWND hWnd, HTREEITEM hItem, HKEY *pRoot, TCHAR *pszKey, INT nMax) { TV_ITEM tvi; TCHAR szName[256]; HTREEITEM hParent; HWND hwndTV = GetDlgItem (hWnd, ID_TREEV); memset (&tvi, 0, sizeof (tvi)); hParent = TreeView_GetParent (hwndTV, hItem); if (hParent) { // Get the parent of the parent of the... GetTree (hWnd, hParent, pRoot, pszKey, nMax); // Get the name of the item. tvi.mask = TVIF_TEXT; tvi.hItem = hItem; tvi.pszText = szName; tvi.cchTextMax = dim(szName); TreeView_GetItem (hwndTV, &tvi); //send the TVM_GETITEM message? lstrcat (pszKey, TEXT ("\\")); lstrcat (pszKey, szName); } else { *pszKey = TEXT ('\0'); szName[0] = TEXT ('\0'); // Get the name of the item. tvi.mask = TVIF_TEXT | TVIF_PARAM; tvi.hItem = hItem; tvi.pszText = szName; tvi.cchTextMax = dim(szName); if (TreeView_GetItem (hwndTV, &tvi)) //*pRoot = (HTREEITEM)tvi.lParam; //original hItem = (HTREEITEM)tvi.lParam; else { INT rc = GetLastError(); } } return 0; } The block of code that begins with the comment "Get the name of the item" does not make sense to me. If you are getting the listview item why does the code set the parameters of the item being retrieved, because if you already had the values there would be no need to retrieve them. Secondly near the comment "original" is the original line of code which will compile with a varning under embedded visual c++, but if you copy the exact same code into visual studio 2008 it will not compile. Since I did not write any of this code and am trying to learn is it possible the original author made a mistake on this line, since the *pRoot should point to and HKEY type yet he is casting to an HTREEITEM type which should never work since the data types don't match? (Side note someone with a better reputation should add a windows ce tag to SO since windows mobile is not the same as windows ce.)

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  • Distributing iPhone App to developers in your team through iTunes

    - by Rudiger
    Hi everyone, Was wondering if you can distribute your App to other developers in your team through iTunes. I guess you would upload the App as a beta version through iTunes Connect and anyone with a provisioned iPhone would receive the update. I didn't think it was possible but someone told me they were sure you could. If this is not possible are there any other benefits of a company standard enrolment besides being able to add other people so they can get the same resources? Thanks

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