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• Efficient way to get highly correlated pairs from large data set in Python or R

  - by Akavall

  I have a large data set (Let's say 10,000 variables with about 1000 elements each), we can think of it as 2D list, something like: [[variable_1], [variable_2], ............ [variable_n] ] I want to extract highly correlated variable pairs from that data. I want "highly correlated" to be a parameter that I can choose. I don't need all pairs to be extracted, and I don't necessarily want the most correlated pairs. As long as there is an efficient method that gets me highly correlated pairs I am happy. Also, it would be nice if a variable does not show up in more than one pair. Although this might not be crucial. Of course, there is a brute force way to finding such pairs, but it is too slow for me. I've googled around for a bit and found some theoretical work on this issue, but I wasn't able for find a package that could do what I am looking for. I mostly work in python, so a package in python would be most helpful, but if there exists a package in R that does what I am looking for it will be great. Does anyone know of a package that does the above in Python or R? Or any other ideas? Thank You in Advance

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• C++ AMP, for loops to parallel_for_each loop

  - by user1430335

  I'm converting an algorithm to make use of the massive acceleration that C++ AMP provides. The stage I'm at is putting the for loops into the known parallel_for_each loop. Normally this should be a straightforward task to do but it appears more complex then I first thought. It's a nested loop which I increment using steps of 4 per iterations: for(int j = 0; j < height; j += 4, data += width * 4 * 4) { for(int i = 0; i < width; i += 4) { The trouble I'm having is the use of the index. I can't seem to find a way to properly fit this into the parallel_for_each loop. Using an index of rank 2 is the way to go but manipulating it via branching will do harm to the performance gain. I found a similar post: Controlling the index variables in C++ AMP. It also deals about index manipulation but the increment aspect doesn't cover my issue. With kind regards, Forcecast

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• Write-Only Reference in C++?

  - by Robert Mason

  Is there a way to code a write-only reference to an object? For example, suppose there was a mutex class: template <class T> class mutex { protected: T _data; public: mutex(); void lock(); //locks the mutex void unlock(); //unlocks the mutex T& data(); //returns a reference to the data, or throws an exception if lock is unowned }; Is there a way to guarantee that one couldn't do this: mutex<type> foo; T& ref; foo.lock(); ref = foo.data(); foo.unlock(); //I have a unguarded reference to foo now On the other hand, is it even worth it? I know that some people assume that programmers won't deliberately clobber the system, but then, why do we have private variables in the first place, eh? It'd be nice to just say it's "Undefined Behavior", but that just seems a little bit too insecure.

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• Prolog Beginner: How to unify with arithmentic cmparison operators or how to get a set var to range

  - by sixtyfootersdude

  I am new to prolog. I need to write an integer adder that will add numbers between 0-9 to other numbers 0-9 and produce a solution 0-18. This is what I want to do: add(in1, in2, out) :- in1 < 10, in2 < 10, out < 18. I would like to be able to call it like this: To Check if it is a valid addition: ?- add(1,2,3). true ?- add(1,2,4). false With one missing variable: ?- add(X,2,3). 1 ?- add(1,4,X). 5 With multiple missing variables: ?-add(X,Y,Z). % Some output that would make sense. Some examples could be: X=1, Y=1, Z=2 ; X=2, Y=1, Z=3 ...... I realize that this is probably a pretty simplistic question and it is probably very straightforward. However cording to the prolog tutorial I am using: "Unlike unification Arithmetic Comparison Operators operators cannot be used to give values to a variable. The can only be evaluated when every term on each side have been instantiated."

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• Does the Java Memory Model (JSR-133) imply that entering a monitor flushes the CPU data cache(s)?

  - by Durandal

  There is something that bugs me with the Java memory model (if i even understand everything correctly). If there are two threads A and B, there are no guarantees that B will ever see a value written by A, unless both A and B synchronize on the same monitor. For any system architecture that guarantees cache coherency between threads, there is no problem. But if the architecture does not support cache coherency in hardware, this essentially means that whenever a thread enters a monitor, all memory changes made before must be commited to main memory, and the cache must be invalidated. And it needs to be the entire data cache, not just a few lines, since the monitor has no information which variables in memory it guards. But that would surely impact performance of any application that needs to synchronize frequently (especially things like job queues with short running jobs). So can Java work reasonably well on architectures without hardware cache-coherency? If not, why doesn't the memory model make stronger guarantees about visibility? Wouldn't it be more efficient if the language would require information what is guarded by a monitor? As i see it the memory model gives us the worst of both worlds, the absolute need to synchronize, even if cache coherency is guaranteed in hardware, and on the other hand bad performance on incoherent architectures (full cache flushes). So shouldn't it be more strict (require information what is guarded by a monitor) or more lose and restrict potential platforms to cache-coherent architectures? As it is now, it doesn't make too much sense to me. Can somebody clear up why this specific memory model was choosen? EDIT: My use of strict and lose was a bad choice in retrospect. I used "strict" for the case where less guarantees are made and "lose" for the opposite. To avoid confusion, its probably better to speak in terms of stronger or weaker guarantees.

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• TDD approach for complex function

  - by jamie

  I have a method in a class for which they are a few different outcomes (based upon event responses etc). But this is a single atomic function which is to used by other applications. I have broken down the main blocks of the functionality that comprise this function into different functions and successfully taken a Test Driven Development approach to the functionality of each of these elements. These elements however aren't exposed for other applications would use. And so my question is how can/should i easily approach a TDD style solution to verifying that the single method that should be called does function correctly without a lot of duplication in testing or lots of setup required for each test? I have considered / looked at moving the blocks of functionality into a different class and use Mocking to simulate the responses of the functions used but it doesn't feel right and the individual methods need to write to variables within the main class (it felt really heath robinson). The code roughly looks like this (i have removed a lot of parameters to make things clearer along with a fair bit of irrelevant code). public void MethodToTest(string parameter) { IResponse x = null; if (function1(parameter)) { if (!function2(parameter,out x)) { function3(parameter, out x); } } // ... // more bits of code here // ... if (x != null) { x.Success(); } }

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• Overwriting a range of bits in an integer in a generic way

  - by porgarmingduod

  Given two integers X and Y, I want to overwrite bits at position P to P+N. Example: int x = 0xAAAA; // 0b1010101010101010 int y = 0x0C30; // 0b0000110000110000 int result = 0xAC3A; // 0b1010110000111010 Does this procedure have a name? If I have masks, the operation is easy enough: int mask_x = 0xF00F; // 0b1111000000001111 int mask_y = 0x0FF0; // 0b0000111111110000 int result = (x & mask_x) | (y & mask_y); What I can't quite figure out is how to write it in a generic way, such as in the following generic C++ function: template<typename IntType> IntType OverwriteBits(IntType dst, IntType src, int pos, int len) { // If: // dst = 0xAAAA; // 0b1010101010101010 // src = 0x0C30; // 0b0000110000110000 // pos = 4 ^ // len = 8 ^------- // Then: // result = 0xAC3A; // 0b1010110000111010 } The problem is that I cannot figure out how to make the masks properly when all the variables, including the width of the integer, is variable. Does anyone know how to write the above function properly?

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• Mathematics errors in basic C++ program

  - by H Bomb1013

  I am working with a basic C++ program to determine the area and perimeter of a rectangle. My program works fine for whole numbers but falls apart when I use any number with a decimal. I get the impression that I am leaving something out, but since I'm a complete beginner, I have no idea what. Below is the source: #include <iostream> using namespace std; int main() { // Declared variables int length; // declares variable for length int width; // declares variable for width int area; // declares variable for area int perimeter; // declares variable for perimeter // Statements cout << "Enter the length and the width of the rectangle: "; // states what information to enter cin >> length >> width; // user input of length and width cout << endl; // closes the input area = length * width; // calculates area of rectangle perimeter = 2 * (length + width); //calculates perimeter of rectangle cout << "The area of the rectangle = " << area << " square units." <<endl; // displays the calculation of the area cout << "The perimeter of the rectangle = " << perimeter << " units." << endl; // displays the calculation of the perimeter system ("pause"); // REMOVE BEFORE RELEASE - testing purposes only return 0; }

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• Retrieve POST data without knowing exact number of fields

  - by James

  Hi all! I'm creating an online poll from scratch which will be held in a database. I'm working on getting a system set up so someone can create a new poll. I will be having the user fill out a simple HTML form with the Questions and Answers (there may be several answers). The user will be able to add multiple questions and multiple answers for each question. As the total number of questions and answers will be decided by the user, I need to create some clever PHP to cater for this - however many there are. When dealing with a static number of questions, it's simple. But I'm having trouble thinking of a way to get all the POST data into individual PHP variables so I can process them. I was thinking of using a foreach loop, anyone got any ideas? Sorry for the long winded description! If anyone needs anything clarified, I'd be happy to do so. My problem is that I can't get my head around how to deal with the POST values when I don't know exactly which element of the array will contain what. If things were static with a set number of questions and answers, I'd know $_POST[0] was Question1, etc Thank you! =)

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• Parallelize or vectorize all-against-all operation on a large number of matrices?

  - by reve_etrange

  I have approximately 5,000 matrices with the same number of rows and varying numbers of columns (20 x ~200). Each of these matrices must be compared against every other in a dynamic programming algorithm. In this question, I asked how to perform the comparison quickly and was given an excellent answer involving a 2D convolution. Serially, iteratively applying that method, like so list = who('data_matrix_prefix*') H = cell(numel(list),numel(list)); for i=1:numel(list) for j=1:numel(list) if i ~= j eval([ 'H{i,j} = compare(' char(list(i)) ',' char(list(j)) ');']); end end end is fast for small subsets of the data (e.g. for 9 matrices, 9*9 - 9 = 72 calls are made in ~1 s). However, operating on all the data requires almost 25 million calls. I have also tried using deal() to make a cell array composed entirely of the next element in data, so I could use cellfun() in a single loop: # who(), load() and struct2cell() calls place k data matrices in a 1D cell array called data. nextData = cell(k,1); for i=1:k [nextData{:}] = deal(data{i}); H{:,i} = cellfun(@compare,data,nextData,'UniformOutput',false); end Unfortunately, this is not really any faster, because all the time is in compare(). Both of these code examples seem ill-suited for parallelization. I'm having trouble figuring out how to make my variables sliced. compare() is totally vectorized; it uses matrix multiplication and conv2() exclusively (I am under the impression that all of these operations, including the cellfun(), should be multithreaded in MATLAB?). Does anyone see a (explicitly) parallelized solution or better vectorization of the problem?

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• Unsure how to come up with a good design

  - by Mewzer

  Hello there, I am having trouble coming up with a good design for a group of classes and was hoping that someone could give me some guidance on best practices. I have kept the classes and member functions generic to make the problem simpler. Essentially, I have three classes (lets call them A, B, and C) as follows: class A { ... int GetX( void ) const { return x; }; int GetY( void ) const { return y; }; private: B b; // NOTE: A "has-a" B int x; int y; }; class B { ... void SetZ( int value ) { z = value }; private: int z; C c; // NOTE: B "has-a" C }; class C { private: ... void DoSomething(int x, int y){ ... }; void DoSomethingElse( int z ){ ... }; }; My problem is as follows: Class A uses its member variables "x" and "y" a lot internally. Class B uses its member variable "z" a lot internally. Class B needs to call C::DoSomething(), but C::DoSomething() needs the values of X and Y in class A passed in as arguments. C::DoSomethingElse() is called from say another class (e.g. D), but it needs to invoke SetZ() in class B!. As you can see, it is a bit of a mess as all the classes need information from one another!. Are there any design patterns I can use?. Any ideas would be much appreciated ....

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• Error compiling basic java code

  - by Michael Younani

  New to java. Practicing coding by following a book. Heres my code: class Motorcycle { //Three instance variables - make and color are strings. while a boolean refers to TRUE OR FLASE(in this case off or on) String make; String color; boolean engineState; void startEngine() { if (engineState == true) System.out.print("The engine is already on."); else { engineState = true; System.out.print("The engine is now on."); } void showAtts() { System.out.print("This motorcycle is a " + color + " " + make); if (engineState ==true) System.out.print("The engine is on."); else System.out.print("The engine is off."); } } } When I compile I get 2 errors: 1) illegal start of expression 2) ; expected I can't pin point the problem. If anyone can direct me or hint me please do.

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• Hiding Url for asp.net page

  - by user204588

  Hello, I'm creating an html page that is posted to another page for processing. I don't want users to see the weird URL they are redirected to and I was using FRAMES but I can't figure out how to add my HTML page dynamically because I need the variables and either add frames or try another way to accomplish this. So, based on how I'm creating the page below, how can I hide the URL and add something that I want. Here is how I'm creating the page. StringBuilder sb = new StringBuilder(); sb.Append("<html><head></head>"); sb.Append("<body onload=\"document.frmLaunch.submit();\">"); sb.Append("<form name=\"frmLaunch\" action=\"" + variableTargetURL + "\" method=\"post\">"); sb.Append("<input type=hidden name=\"testVariable\" value=\"" + variableTest + "\">"); sb.Append("</form>"); sb.Append("</body></html>"); HttpResponse response = HttpContext.Current.Response; response.Clear(); response.Write(sb.ToString()); response.End();

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• Images won't load if they are of high size

  - by Fahim Parkar

  I have created web-application using JSF 2.0 and mysql. I am storing images in DB using MEDIUMBLOB. When I try to load image, I am able to see those images. However if the image size is big (1 MB or more), I can see half or 3/4th image on the browser. Any idea how to overcome this issue? Do I need to set any variable in JSF or MySQL? I know I should have saved the images over disk instead of DB, however this was client requirement. Client wanted to backup data and provide it to someone else and client don't want to backup DB and images also. Edit 1 Do I need to set any variables on mysql like query_cache. Edit 2 When I download same image and put below code it works perfectly. <h:graphicImage value="images/myImage4.png" width="50%" /> Edit 3 code is as below. <h:graphicImage value="DisplayImage?mainID=drawing" /> DisplayImage.java String imgLen = rs1.getString(1); int len = imgLen.length(); byte[] rb = new byte[len]; InputStream readImg = rs1.getBinaryStream(1); InputStream inputStream = readImg; int index = readImg.read(rb, 0, len); response.reset(); response.setHeader("Content-Length", String.valueOf(len)); response.setHeader("Content-disposition", "inline;filename=/file.png"); response.setContentType("image/png"); response.getOutputStream().write(rb, 0, len); response.getOutputStream().flush(); When I print len I get value as len=1548432

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• Getting information from servlet created html

  - by user541597

  I have a servlet that creates an html text box and then redirects to another servlet on submit. How can I access the value of the html text box from the new servlet? I am able to access servlet variables from the new servlet but I am not aware of how to access the value of the html generated code. thanks, Here is the servlet that gets the text input public class ServletB extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); String value = System.getProperty("card"); PrintWriter out = response.getWriter(); out.println("<center><h1>Your preffered method of payment is "+value+"</h1><br />"); out.println("Please Enter Card Number<input type =\"text\" name = \"number\"/><form action=\"http://codd.cs.gsu.edu:9999/cpereyra183/servlet/ServletC\"><input type =\"submit\" value=\"Continue\" /><input type=\"button\" value=\"Cancel\" /></center>"); } }} This is the servlet the first servlet redirects to all I do is try to do is output the text input public class ServletC extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); String value = System.getProperty("card"); PrintWriter out = response.getWriter(); out.println(request.getParameter("number")); } }

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• c++ code cons/pros

  - by VirusEcks

  below i have a code that runs in most of my simple programs .. . i want to know if it's good/bad ... and cons/pros . . win32 header file: win32.h #include <windows.h> #include <process.h> #include <stdarg.h> main header file: inc.h #include "win32.h" #ifndef INCS #define INCS #define DD #else #define DD extern #endif #ifndef VARS #define titlen L"my program" #endif DD wchar_t gtitle[512]; DD wchar_t gclass[512]; DD wchar_t gdir[32767]; #include "resources.h" #include "commonfunctions.h" then all files have something like this commonfunctions.h DD inline bool icmp( const char *String1, const char *String2 ) { if ( _stricmp( String1, String2 ) == 0 ) { return true; } return false; } DD inline bool scmp( const char *String1, const char *String2 ) { if ( strcmp( String1, String2 ) == 0 ) { return true; } return false; } all global variables have DD infront of them and all functions have DD too . is there a bad side of this ? . i came up with this idea and it wasn't problematic at all in small programs . but before i apply it in a large project will it be problematic ?. thanks in advance.

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• Help regarding multi-threading in MFC,please help me firends!

  - by kiddo

  Hello all,in my application there is a small part of function,in which it will read files to get some information,the number of filecount would be utleast 50,So I thought of implementing threading.Say if the user is giving 50 files,I wanted to separate it as 5 *10, 5 thread should be created,so that each thread can handle 10 files which can speed up the process.And also from the below code you can see that some variables are common.I read some articles about threading and I am aware that only one thread should access a variable/contorl at a me(CCriticalStiuation can be used for that).For me as a beginner,I am finding hard to imlplement what I have learned about threading.Somebody please give me some idea with code shown below..thanks in advance file read function:// void CMyClass::GetWorkFilesInfo(CStringArray& dataFilesArray,CString* dataFilesB, int* check,DWORD noOfFiles,LPWSTR path) { CString cFilePath; int cIndex =0; int exceptionInd = 0; wchar_t** filesForWork = new wchar_t*[noOfFiles]; int tempCheck; int localIndex =0; for(int index = 0;index < noOfFiles; index++) { tempCheck = *(check + index); if(tempCheck == NOCHECKBOX) { *(filesForWork+cIndex) = new TCHAR[MAX_PATH]; wcscpy(*(filesForWork+cIndex),*(dataFilesB +index)); cIndex++; } else//CHECKED or UNCHECKED { dataFilesArray.Add(*(dataFilesB+index)); *(check + localIndex) = *(check + index); localIndex++; } } WorkFiles(&cFilePath,dataFilesArray,filesForWork, path, cIndex); dataFilesArray.Add(cFilePath); *(check + localIndex) = CHECKED; }

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• C++ privately contructed class

  - by Nona Urbiz

  How can I call a function and keep my constructor private? If I make the class static, I need to declare an object name which the compiler uses to call the constructor, which it cannot if the constructor is private (also the object would be extraneous). Here is the code I am attempting to use (it is not compilable): I want to keep the constructor private because I will later be doing a lot of checks before adding an object, modifying previous objects when all submitted variables are not unique rather than creating new objects. #include <iostream> #include <fstream> #include <regex> #include <string> #include <list> #include <map> using namespace std; using namespace tr1; class Referral { public: string url; map<string, int> keywords; static bool submit(string url, string keyword, int occurrences) { //if(Referrals.all.size == 0){ // Referral(url, keyword, occurrences); //} } private: list<string> urls; Referral(string url, string keyword, int occurrences) { url = url; keywords[keyword] = occurrences; Referrals.all.push_back(this); } }; struct All { list<Referral> all; }Referrals; int main() { Referral.submit("url", "keyword", 1); }

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• NullPointerException on Activity Testint Tutorial

  - by Bendik

  Hello, I am currently trying the activity testing tutorial (Found here), and have a problem. It seems that whenever I try to call something inside the UIThread, I get a java.lang.NullPointerException. public void testSpinnerUI() { mActivity.runOnUiThread( new Runnable() { public void run() { mSpinner.requestFocus(); } }); } This gives me: Incomplete: java.lang.NullPointerException and nothing else. I have tried this on two different samples now, with the same result. I tried with a try/catch clause around the mSpinner.requestFocus() call, and it seems that mSpinner is null inside the thread. I have set it properly up with the setUp() function found in the same sample, and a quick assertNotNull( mSpinner ) shows me that mSpinner is in fact not null after the setUp() function. What can be the cause of this? EDIT; ok, some more testing has been done. It seems that the application that is being tested resets between each test. This essentially makes me have to reinstantiate all variables between each test. Is this normal?

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• How to send java.util.logging to log4j?

  - by matt b

  I have an existing application which does all of its logging against log4j. We use a number of other libraries that either also use log4j, or log against Commons Logging, which ends up using log4j under the covers in our environment. One of our dependencies even logs against slf4j, which also works fine since it eventually delegates to log4j as well. Now, I'd like to add ehcache to this application for some caching needs. Previous versions of ehcache used commons-logging, which would have worked perfectly in this scenario, but as of version 1.6-beta1 they have removed the dependency on commons-logging and replaced it with java.util.logging instead. Not really being familiar with the built-in JDK logging available with java.util.logging, is there an easy way to have any log messages sent to JUL logged against log4j, so I can use my existing configuration and set up for any logging coming from ehcache? Looking at the javadocs for JUL, it looks like I could set up a bunch of environment variables to change which LogManager implementation is used, and perhaps use that to wrap log4j Loggers in the JUL Logger class. Is this the correct approach? Kind of ironic that a library's use of built-in JDK logging would cause such a headache when (most of) the rest of the world is using 3rd party libraries instead.

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• Could someone help me debug my app (not very big)?

  - by Alex

  Not sure if this kind of help is accepted to ask for here, tell me if it isn't. It has to get done before tomorrow, it's not entirerly finished but it should work somewhat ok by now. I'm trying to use the Eclipse debugger (not very used to it). I have my top-level or main class, which is Game, in which I have a constructor and a main method. In the main method I create a new "Game", initiating the constructor. public static void main(String[] args){ Game chess = new Game(); } public Game(){ Board board = new Board(); That's the first thing the debugger reacts to: Thread [main] (Suspended) ClassNotFoundException(Object).<init>() line: 20 [local variables unavailable] ClassNotFoundException(Throwable).<init>(String, Throwable) line: 217 ClassNotFoundException(Exception).<init>(String, Throwable) line: not available ClassNotFoundException.<init>(String) line: not available URLClassLoader$1.run() line: not available AccessController.doPrivileged(PrivilegedExceptionAction<T>, AccessControlContext) line: not available [native method] Launcher$ExtClassLoader(URLClassLoader).findClass(String) line: not available Launcher$ExtClassLoader.findClass(String) line: not available Launcher$ExtClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader.loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String) line: not available Game.<init>() line: 15 Game.main(String[]) line: 11 Line 11 is the one line in my main method, line 15 is the instantiation of "board".

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• Persisting object changes from child form to parent form based on button press.

  - by Shyran

  I have created a form that is used for both adding and editing a custom object. Which mode the form takes is provided by an enum value passed from the calling code. I also pass in an object of the custom type. All of my controls at data bound to the specific properties of the custom object. When the form is in Add mode, this works great as when the controls are updated with data, the underlying object is as well. However, in Edit mode, I keep two variables of the custom object supplied by the calling code, the original, and a temporary one made through deep copying. The controls are then bound to the temporary copy, this makes it easy to discard the changes if the user clicks the Cancel button. What I want to know is how to persist those changes back to the original object if the user clicks the OK button, since there is now a disconnect because of the deep copying. I am trying to avoid implementing a internal property on the Add/Edit form if I can. Below is an example of my code: public AddEditCustomerDialog(Customer customer, DialogMode mode) { InitializeComponent(); InitializeCustomer(customer, mode); } private void InitializeCustomer(Customer customer, DialogMode mode) { this.customer = customer; if (mode == DialogMode.Edit) { this.Text = "Edit Customer"; this.tempCustomer = ObjectCopyHelper.DeepCopy(this.customer); this.customerListBindingSource.DataSource = this.tempCustomer; this.phoneListBindingSource.DataSource = this.tempCustomer.PhoneList; } else { this.customerListBindingSource.DataSource = this.customer; this.phoneListBindingSource.DataSource = this.customer.PhoneList; } }

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• ReplaceAll not working as expected

  - by Tim Kemp

  Still early days with Mathematica so please forgive what is probably a very obvious question. I am trying to generate some parametric plots. I have: ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} No joy: the replacement rules are not applied and a, b and h remain undefined. If I instead do: Hold@ParametricPlot[{ (a + b) Cos[t] - h Cos[(a + b)/b t], (a + b) Sin[t] - h Sin[(a + b)/b t]}, {t, 0, 2 \[Pi]}, PlotRange -> All] /. {a -> 2, b -> 1, h -> 1} it looks like the rules ARE working, as confirmed by the output: Hold[ParametricPlot[{(2 + 1) Cos[t] - 1 Cos[(2 + 1) t], (2 + 1) Sin[t] - 1 Sin[(2 + 1) t]}, {t, 0, 2 \[Pi]}, PlotRange -> All]] Which is what I'd expect. Take the Hold off, though, and the ParametricPlot doesn't work. There's nothing wrong with the equations or the ParametricPlot itself, though, because I tried setting values for a, b and h in a separate expression (a=2; b=1; h=1) and I get my pretty double cardoid out as expected. So, what am I doing wrong with ReplaceAll and why are the transformation rules not working? This is another fundamentally important aspect of MMA that my OOP-ruined brain isn't understanding. I tried reading up on ReplaceAll and ParametricPlot and the closest clue I found was that "ParametricPlot has attribute HoldAll and evaluates f only after assigning specific numerical values to variables" which didn't help much or I wouldn't be here. Thanks.

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• Need help getting buttons to work...

  - by Mike Droid

  I am trying to get my first button to update a display number in my view when clicked. This view will have several buttons and "outputs" displayed. After reading examples and Q's here, I finally put something together that runs, but my first button is still not working; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.ship_layout); mSwitcher = (TextSwitcher) findViewById(R.id.eng_val); } private TextSwitcher mSwitcher; // Will be connected with the buttons via XML void onClick(View v){ switch (v.getId()) { case R.id.engplus: engcounter++; updateCounter(); break; case R.id.engneg: engcounter--; updateCounter(); break; } } private void updateCounter() { mSwitcher.setText(String.valueOf(engcounter)); } The .xml for this button is; <TextSwitcher android:id="@+id/eng_val" android:visibility="visible" android:paddingTop="9px" android:paddingLeft="50px" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/build" android:layout_toRightOf="@+id/engeq" android:textColor="#DD00ff00" android:textSize="24sp"/> This is within a Relative Layout that appears otherwise OK. When I had set the view to have a TextView with the number set as a string , the number displayed, but I could not figure out how to update the text with a numerical field. That may be my real problem. I have gone through many examples generally referenced from the dev. site (UI, Common Tasks, various samples), and I am still not seeing the connection here... Again, this is simply a try at getting variables to respond to buttons and update on the view. So, a few Q's for anyone that can help; 1) Is there any easier way of doing this (ie. send numerical value to View) ? 2) Why isn't my TextSwitcher displaying the number? 3) Should I be using a TextSwitcher here? 4) Any examples of this you can point me to?

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• game currency convert: math efficient

  - by Comradsky

  For variables:4 text views named diamondText, goldText, silverText, and bronzeText;money variable unsigned int money;and an NSTimer, every .1 sec,runs function: -(void)updateMoney{ money++; bronzeText.text = [NSString stringWithFormat:@"%d",money]; silverText.text = [NSString stringWithFormat:@"%d",money%10]; goldText.text = [NSString stringWithFormat:@"%d",money%100]; diamondText.text= [NSString stringWithFormat:@"%d",money%1000]; } Given that my currency is diamond = 10 gold = 10 silver = 10 bronze = 1; What would be most efficient way to calculate and display the money labels? How would you store this variable, with GameCenter and NSDictionary or GameCenter and something else? More details are below if you don't understand. To clarify: bronze has the last 2 numbers, silver has the next 2 numbers, and so on. I understand I could use 4 ints or an array, but i would rather try to use this method, unless theres a much more efficient way. Example: When money = 1000;bronzeText = nothing, silverText = 10,goldText = nothing, diamondText = nothing; What other ways would you do this that you think would be more efficient? I will be calling a function (void)collisionDetector that detects if my player.frame crosses with a flyingObject.frame, and if that object is a coin it gives an added value to money and then calls (void)updateMoney. Im just using the timer to test this and spawn these flying objects.

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