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• Reuse C++ Header files

  - by Amrish

  Guys, I have a Visual C++ solution with 2 projects AlgorithmA & AlgorithmB and both share a common header file RunAlgo.h with the class declaration. Each project in the solution has its own unique implementation for the header file. I am trying to compile a DLL out of the common header file RunAlgo.h and add reference to this DLL in the projects AlgorithmA & AlgorithmB. I have then included separate RunAlgo.cpp definition file in both my projects. The problem is that I am getting linker errors while compiling the new DLL project which has only the header file. So, the question is Can a header file with only class declaration be compiled into a DLL (Similar to class library containing an Interface in C#)? For the above scenario, is there a better approach to reuse the common Header file among projects? Should the above method work (re-check my code?)

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• Parallelizing a serial algorithm

  - by user643813

  Hej folks, I am working on porting a Text mining/Natural language application from single-core to a Map-Reduce style system. One of the steps involves a while loop similar to this: Queue<Element>; while (!queue.empty()) { Element e = queue.next(); Set<Element> result = calculateResultSet(e); if (!result.empty()) { queue.addAll(result); } } Each iteration depends on the result of the one before (kind of). There is no way of determining the number of iterations this loop will have to perform. Is there a way of parallelizing a serial algorithm such as this one? I am trying to think of a feedback mechanism, that is able to provide its own input, but how would one go about parallelizing it? Thanks for any help/remarks

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• Segfault when calling a method c++

  - by shuttle87

  I am fairly new to c++ and I am a bit stumped by this problem. I am trying to assign a variable from a call to a method in another class but it always segfaults. My code compiles with no warnings and I have checked that all variables are correct in gdb but the function call itself seems to cause a segfault. The code I am using is roughly like the following: class History{ public: bool test_history(); }; bool History::test_history(){ std::cout<<"test"; //this line never gets executed //more code goes in here return true; } class Game{ private: bool some_function(); public: History game_actions_history; bool local_variable; }; bool Game::some_function(){ local_variable = game_actions_history.test_history(); if (local_variable == true){ return true; } else{ return false; } } Any tips or advice is greatly appreciated!

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• undefined reference to static member variable

  - by Max

  Hi. I have this class that has a static member. it is also a base class for several other classes in my program. Here's its header file: #ifndef YARL_OBJECT_HPP #define YARL_OBJECT_HPP namespace yarlObject { class YarlObject { // Member Variables private: static int nextID; // keeps track of the next ID number to be used int ID; // the identifier for a specific object // Member Functions public: YarlObject(): ID(++nextID) {} virtual ~YarlObject() {} int getID() const {return ID;} }; } #endif and here's its implementation file. #include "YarlObject.hpp" namespace yarlObject { int YarlObject::nextID = 0; } I'm using g++, and it returns three undefined reference to 'yarlObject::YarlObject::nextID linker errors. If I change the ++nextID phrase in the constructor to just nextID, then I only get one error, and if I change it to 1, then it links correctly. I imagine it's something simple, but what's going on?

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• bulk update/delete entities of different kind in db.run_in_transaction

  - by Ray Yun

  Here goes pseudo code of bulk update/delete entities of different kind in single transaction. Note that Album and Song entities have AlbumGroup as root entity. class AlbumGroup: pass class Album: group = db.ReferenceProperty(reference_class=AlbumGroup,collection_name="albums") class Song: album = db.ReferenceProperty(reference_class=Album,collection_name="songs") def bulk_update_album_group(album_group): updated = [album_group] deleted = [] for album in album_group.albums: updated.append(album) for song in album.songs: if song.is_updated: updated.append(song) if song.is_deleted: deleted.append(song) db.put(updated) db.delete(deleted) a = AlbumGroup.all().filter("...").get() # bulk update/delete album group. for simplicity, album cannot be deleted. db.run_in_transaction(bulk_update_album_group,a) But I met a famous "Only Ancestor Queries in Transactions" error at the iterating reference properties like album.songs or album_group.albums. I guess ancestor() filter does not help because those entities are modified in memory. Should I not to iterate reference property in transaction function and always provide them as function parameters like def bulk_update_album_group(updated,deleted): ??? Is there any good coding pattern for this situation?

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• [C++] std::string manipulation: whitespace, "newline escapes '\'" and comments #

  - by rubenvb

  Kind of looking for affirmation here. I have some hand-written code, which I'm not shy to say I'm proud of, which reads a file, removes leading whitespace, processes newline escapes '\' and removes comments starting with #. It also removes all empty lines (also whitespace-only ones). Any thoughts/recommendations? I could probably replace some std::cout's with std::runtime_errors... but that's not a priority here :) const int RecipeReader::readRecipe() { ifstream is_recipe(s_buffer.c_str()); if (!is_recipe) cout << "unable to open file" << endl; while (getline(is_recipe, s_buffer)) { // whitespace+comment removeLeadingWhitespace(s_buffer); processComment(s_buffer); // newline escapes + append all subsequent lines with '\' processNewlineEscapes(s_buffer, is_recipe); // store the real text line if (!s_buffer.empty()) v_s_recipe.push_back(s_buffer); s_buffer.clear(); } is_recipe.close(); return 0; } void RecipeReader::processNewlineEscapes(string &s_string, ifstream &is_stream) { string s_temp; size_t sz_index = s_string.find_first_of("\\"); while (sz_index <= s_string.length()) { if (getline(is_stream,s_temp)) { removeLeadingWhitespace(s_temp); processComment(s_temp); s_string = s_string.substr(0,sz_index-1) + " " + s_temp; } else cout << "Error: newline escape '\' found at EOF" << endl; sz_index = s_string.find_first_of("\\"); } } void RecipeReader::processComment(string &s_string) { size_t sz_index = s_string.find_first_of("#"); s_string = s_string.substr(0,sz_index); } void RecipeReader::removeLeadingWhitespace(string &s_string) { const size_t sz_length = s_string.size(); size_t sz_index = s_string.find_first_not_of(" \t"); if (sz_index <= sz_length) s_string = s_string.substr(sz_index); else if ((sz_index > sz_length) && (sz_length != 0)) // "empty" lines with only whitespace s_string.clear(); } Some extra info: the first s_buffer passed to the ifstream contains the filename, std::string s_buffer is a class data member, so is std::vector v_s_recipe. Any comment is welcome :)

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• Can't run the ActionBarCompat sample

  - by David Miler

  I am having trouble compiling and running the ActionBarCompat sample of Android 16. I have API level 16 as the build target selected, which seems to build fine, but when I try to debug these errors pop up. Of course I could change the min API level in the manifest, but what would be the point of that? I have made no changes to the sample, so how come it is not working properly? Class requires API level 14 (current min is 3): android.view.ActionProvider SimpleMenuItem.java /ActionBarCompat/src/com/example/android/actionbarcompat line 129 Android Lint Problem Class requires API level 14 (current min is 3): android.view.ActionProvider SimpleMenuItem.java /ActionBarCompat/src/com/example/android/actionbarcompat line 134 Android Lint Problem Class requires API level 14 (current min is 3): android.view.MenuItem.OnActionExpandListener SimpleMenuItem.java /ActionBarCompat/src/com/example/android/actionbarcompat line 155 Android Lint Problem I am thoroughly confused, any help would be appreciated.

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• Are table headers only for the top row in html?

  - by Bill Zimmerman

  Hi, I always see the th tag only used in the first row of the table. Is there some specific reason why it can't be used to create 'left' headers along the leftmost column. Is this bad form, or is this ok. Basically, a table with headings on the top row and the leftmost column, with the very top left square being empty. e.g. <table> <tr> <th/> <!--empty--> <th>Top 1</th> <th>Top 2</th></tr> <tr> <th>LeftHeader?</th> <td>data1</td> <td>data2</td></tr> </table>

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• Dynamically load a type from an external assembly

  - by Water Cooler v2

  From managed code, how do I load a managed type from another assembly at runtime, assuming the calling code does not have a static reference to the assembly? To clarify, let's say I have class Lib in Lib.cs compiled into Lib.dll. I want to write a class Foo in a separate assembly called Foo.dll, that does not have a reference to Lib.dll statically, but instead loads Lib.dll and then reflects on for the presence of the class Lib and then calls a method on it. Sorry for such an obvious question on Reflection. I figure it'll take much lesser time to get the answer on a forum that to read a few articles.

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• Receive messages for derived types in MVVMLight

  - by Hrvoje

  Shouldn't this test pass: [TestMethod] public void derived_message_subscription() { bool handled = false; Messenger.Default.Register<GenericMessage<baseClass>>(this, true, (msg) => handled = true); Messenger.Default.Send(new GenericMessage<testClass>(new testClass())); Assert.IsTrue(handled); } public abstract class baseClass { } public class testClass : baseClass { } I have to receive all messages for classes that inherits from one base class. MVVMLight has bool property receiveDerivedMessagesToo in Register method, but it seems to me that it isn't working.

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• Problem overridding virtual function

  - by William

  Okay, I'm writing a game that has a vector of a pairent class (enemy) that s going to be filled with children classes (goomba, koopa, boss1) and I need to make it so when I call update it calls the childclasses respective update. I have managed to create a example of my problem. #include <stdio.h> class A{ public: virtual void print(){printf("Hello from A");} }; class B : public A{ public: void print(){printf("Hello from B");} }; int main(){ A ab = B(); ab.print(); while(true){} } Output wanted: "Hello from B" Output got: "Hello from A" How do I get it to call B's print function?

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• how to use multiple $_name using extends Zend_Db_Table_Abstract in zend frame work.

  - by karthik

  we tried to give our tables(users,messages) like this in two different abstract classes but it is not working. This is included in a file childconnect1.php ,is there any relation between the file name(childconnect1.php) and the class(Application_Model_childconnect1). class Application_Model_childconnect1 extends Zend_Db_Table_Abstract { protected $_name = 'users'; public function loginvalidation($username,$pwd) { $row = $this->fetchRow('UserName = \'' . $username . '\'and UserPW = \''. $pwd . '\''); if (!$row) { $msg="invalid"; return $msg; } else { return $row->toArray(); } } } class Application_Model_childconnect2 extends Zend_Db_Table_Abstract { protected $_name = 'messages'; public function replymessage($message) { $data=array( 'MessageText'=>$message ); $this->insert($data); } }

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• Does AsEnumerable() cache all result (LINQ)

  - by Akshay

  When we call a query operator on a sequence, a sequence-specific operator gets called. I mean if i call Where<>() operator on IEnumerable<>, the operator that will be called will be defined in Enumerable class and if it's called on IQueryable<>, the one defined in Queryable class will be called. Consider the operator Reverse, defined in the Enumerable class. If i want to call it on Iqueryable<> then I must use the AsEnumerable<>() operator to first convert it into IEnumerable<>. db.Countries.OrderBy(cntry=>cntry.CountryName).AsEnumerable().Reverse() But the Reverse operator got to have all records at the same time so that it can reverse them. In the above code do all the records get loaded in memory first and then the Reverse() operator is reversing it ?

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• indicate tuncation in ToolTipStatusLabel automatically

  - by harper

  I have a .NET application with a StatusStrip holding three ToolTipStatusLabels. The Text of the labels are filled from the application as they show the status. For some circumstances they can hold an empty text. When I resize the window, the ToolTipStatusLabels are hidden when they cannot be fit in the StatusStrip. I would like to have the text truncated when the label cannot be fit in the StatusStrip. The default behavior to hide the label makes it difficult to distinguish between empty text or hidden label. To indicate that the text is truncated automatically, this should be indicated with an ellipsis (...). How can this be done?

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• Passing markup into a Rails Partial

  - by 1ndivisible

  Is there any way of doing something equivilant to this: <%= render partial: 'shared/outer' do %> <%= render partial: 'shared/inner' %> <% end %> Resulting in <div class="outer"> <div class="inner"> </div> </div> Obviously there would need to be a way of marking up 'shared/outer.html.erb' to indicate where the passed in partial should be rendered: <div class="outer"> <% render Here %> </div>

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• When is it safe to do a Response.Redirect() without throwing an exception?

  - by DDechant

  I have an intermediary class extending System.Web.UI.Page for all of my pages that require authentication. The class mostly does custom authentication handling. When a user with insufficient access attempts to visit a page, I try to redirect the user back to the login page while preventing any further page events from being executed (ie. Page_load). The first solution that came to mind was the default implementation of Response.Redirect. Of course the downside to this is the possibility of ThreadAbortExceptions being thrown. So my question is this: When (if at all) during the page life cycle is it actually safe to execute Response.Redirect() without ThreadAbortException ever being thrown? public class CustomPage : System.Web.UI.Page { protected override void OnInit(EventArgs e) { base.OnInit(e); if (!IsValid()) Response.Redirect("login.aspx", true); } }

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• what the java command's -jar option really does

  - by JBoy

  Does the -jar option of the java command also compile the sources before running the main method? I believe so but i would like to have a better understanding of the internal process, from the man page you can clearly see a small workflow sequence: -jar Execute a program encapsulated in a JAR file. The first argument is the name of a JAR file instead of a startup class name. In order for this option to work, the manifest of the JAR file must contain a line of the form Main-Class: classname. Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point. See the Jar tool reference page and the Jar trail of the Java Tutorial @ But it does not mention that it compiles the sources.

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• Buffering db inserts in multithreaded program

  - by Winter

  I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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• What's the fastest way to compare two objects in PHP?

  - by johnnietheblack

  Let's say I have an object - a User object in this case - and I'd like to be able to track changes to with a separate class. The User object should not have to change it's behavior in any way for this to happen. Therefore, my separate class creates a "clean" copy of it, stores it somewhere locally, and then later can compare the User object to the original version to see if anything changed during its lifespan. Is there a function, a pattern, or anything that can quickly compare the two versions of the User object? Option 1 Maybe I could serialize each version, and directly compare, or hash them and compare? Option 2 Maybe I should simply create a ReflectionClass, run through each of the properties of the class and see if the two versions have the same property values? Option 3 Maybe there is a simple native function like objects_are_equal($object1,$object2);? What's the fastest way to do this?

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• scroll bar in textareas

  - by Hulk

  Int the following code, The scroll bar appears in IE and in mozilla it doesnt,how is this to be fixed,scroll bar should not appear where there is not much of data. <script> var row= '<table><tr>'; row = '<tr class="display_row"">'; row += '<td class="display_col" wrap width="75"><b><textarea rows = "8" cols = "18" border ="1" class="input" style="border: none;overflow:visible;width:95%;" readonly maxlength="5">Name selected is Tom </textarea>'; row+='</td></tr></table>'; </script>

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• How to make pytest display a custom string representation for fixture parameters?

  - by Björn Pollex

  When using builtin types as fixture parameters, pytest prints out the value of the parameters in the test report. For example: @fixture(params=['hello', 'world'] def data(request): return request.param def test_something(data): pass Running this with py.test --verbose will print something like: test_example.py:7: test_something[hello] PASSED test_example.py:7: test_something[world] PASSED Note that the value of the parameter is printed in square brackets after the test name. Now, when using an object of a user-defined class as parameter, like so: class Param(object): def __init__(self, text): self.text = text @fixture(params=[Param('hello'), Param('world')] def data(request): return request.param def test_something(data): pass pytest will simply enumerate the number of values (p0, p1, etc.): test_example.py:7: test_something[p0] PASSED test_example.py:7: test_something[p1] PASSED This behavior does not change even when the user-defined class provides custom __str__ and __repr__ implementations. Is there any way to make pytest display something more useful than just p0 here? I am using pytest 2.5.2 on Python 2.7.6 on Windows 7.

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• Using stored procedures to generate RDLC report in C#

  - by NDraskovic

  I'm making an application that generates reports for my client. I'm using his database that contains stored procedures which return the data needed for the reports. The problem is that I don't know how to execute them from the application (more specific the TableAdapter in my dataset). When I use the visual aid to create the TableAdapter, it shows the error "Invalid object named #table1". This is weird because there is a temporary table called #table1 in the stored procedure. When I try to do the whole job programmatically, I get the exception Incorrect syntax near '.'. An object or column name is missing or empty. For SELECT INTO statements, verify each column has a name. For other statements, look for empty alias names. Aliases defined as "" or [] are not allowed. Change the alias to a valid name. I created a DataTable that has identical structure as the result of the stored procedure, but I still get the same exception

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• JQuery Validation Plugin not working when used on page that includes another page via AJAX

  - by droidy

  We have a long page that contains a bunch of different form elements. One part of the form is called remotely via AJAX and is populated in an empty div. This is the part which JQuery Validation plugin is not working correctly on. We have class="required" on the elements on this page, but they do not show up as required. I'm guessing it's because the Validation plugin is looking for class="required" on our main page, and since the content from the AJAX page is put into the empty div behind the scenes, it's not detected the required fields. Any help is greatly appreciated.

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• jsp update request happens to be invoked by a link

  - by Akshatha

  <tr class="bg-row1"> <td class="td-highlighted-2"> <div align="left"><a href="<%=contextPath%>/jsp/admin/UpdateProject.jsp"><%=searchList1.getProjid()%></a></div> </td> <td class="td-highlighted-2"> <div align="left"><%=searchList1.getProjname()%></div> </td> </tr> here jsp update request happens to be invoked by a link in updateproject.jsp how can i refer projid and projname value in a text box

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• Pattern for database-wrapper in java

  - by Space_C0wb0y

  I am currently writing a java-class that wraps an SQLite database. This class has two ways to be instantiated: Open an existing database. Create a new database. This is what I cam up with: public class SQLiteDatabaseWrapper { public static SQLiteDatabaseWrapper openExisting(File PathToDB) { return new SQLiteDatabaseWrapper(PathToDB); } public static SQLiteDatabaseWrapper createNew(File PathToDB) { CreateAndInitializeNewDatabase(PathToDB); return new SQLiteDatabaseWrapper(PathToDB); } private SQLiteDatabaseWrapper(File PathToDB) { // Open connection and setup wrapper } } Is this the way to go in Java, or is there any other best practice for this situation?

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