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  • How do I define a template class and divide it into multiple files?

    - by hkBattousai
    I have written a simple template class for test purpose. It compiles without any errors, but when I try to use it in main(), it give some linker errors. main.cpp #include <iostream> #include "MyNumber.h" int wmain(int argc, wchar_t * argv[]) { MyNumber<float> num; num.SetValue(3.14); std::cout << "My number is " << num.GetValue() << "." << std::endl; system("pause"); return 0; } MyNumber.h #pragma once template <class T> class MyNumber { public: MyNumber(); ~MyNumber(); void SetValue(T val); T GetValue(); private: T m_Number; }; MyNumber.cpp #include "MyNumber.h" template <class T> MyNumber<T>::MyNumber() { m_Number = static_cast<T>(0); } template <class T> MyNumber<T>::~MyNumber() { } template <class T> void MyNumber<T>::SetValue(T val) { m_Number = val; } template <class T> T MyNumber<T>::GetValue() { return m_Number; } When I build this code, I get the following linker errors: Error 7 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\X64\Debug\Console Demo.exe 1 error LNK1120: 4 unresolved externals Error 3 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: __cdecl MyNumber::~MyNumber(void)" (??1?$MyNumber@M@@QEAA@XZ) referenced in function wmain Error 6 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: __cdecl MyNumber::MyNumber(void)" (??0?$MyNumber@M@@QEAA@XZ) referenced in function wmain Error 4 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: float __cdecl MyNumber::GetValue(void)" (?GetValue@?$MyNumber@M@@QEAAMXZ) referenced in function wmain Error 5 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: void __cdecl MyNumber::SetValue(float)" (?SetValue@?$MyNumber@M@@QEAAXM@Z) referenced in function wmain But, if I leave main() empty, I don't get any linker errors. What is wrong with my template class? What am I doing wrong?

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  • EJB failure to update datamodel

    - by Ignacio
    Here my EJB @Entity @Table(name = "modelos") @NamedQueries({ @NamedQuery(name = "Modelos.findAll", query = "SELECT m FROM Modelos m"), @NamedQuery(name = "Modelos.findById", query = "SELECT m FROM Modelos m WHERE m.id = :id"), @NamedQuery(name = "Modelos.findByDescripcion", query = "SELECT m FROM Modelos m WHERE m.descripcion = :descripcion")}) public class Modelos implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Basic(optional = false) @Column(name = "id") private Integer id; @Basic(optional = false) @Column(name = "descripcion") private String descripcion; @OneToMany(cascade = CascadeType.ALL, mappedBy = "idModelo") private Collection produtosCollection; @JoinColumn(name = "id_marca", referencedColumnName = "id") @ManyToOne(optional = false) private Marcas idMarca; public Modelos() { } public Modelos(Integer id) { this.id = id; } public Modelos(Integer id, String descripcion) { this.id = id; this.descripcion = descripcion; } public Modelos(Integer id, Marcas idMarca) { this.id = id; this.idMarca = idMarca; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getDescripcion() { return descripcion; } public void setDescripcion(String descripcion) { this.descripcion = descripcion; } public Collection<Produtos> getProdutosCollection() { return produtosCollection; } public void setProdutosCollection(Collection<Produtos> produtosCollection) { this.produtosCollection = produtosCollection; } public Marcas getIdMarca() { return idMarca; } public void setIdMarca(Marcas idMarca) { this.idMarca = idMarca; } @Override public int hashCode() { int hash = 0; hash += (id != null ? id.hashCode() : 0); return hash; } @Override public boolean equals(Object object) { // TODO: Warning - this method won't work in the case the id fields are not set if (!(object instanceof Modelos)) { return false; } Modelos other = (Modelos) object; if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) { return false; } return true; } @Override public String toString() { return "" + descripcion + ""; } } And the method accesing from the Modelosfacade public List findByMarcas(Marcas idMarca){ return em.createQuery("SELECT id, descripcion FROM Modelos WHERE idMarca = "+idMarca.getId()+"").getResultList(); } And the calling method from the controller public String createByMarcas() { //recreateModel(); items = new ListDataModel(ejbFacade.findByMarcas(current.getIdMarca())); updateCurrentItem(); System.out.println(current.getIdMarca()); return "List"; } I do not understand why I keep falling in an EJB exception.

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  • Inserting newlines into a GtkTextView widget (GTK+ programming)

    - by Mark Roberts
    I've got a button which when clicked copies and appends the text from a GtkEntry widget into a GtkTextView widget. (This code is a modified version of an example found in the "The Text View Widget" chapter of Foundations of GTK+ Development.) I'm looking to insert a newline character before the text which gets copied and appended, such that each line of text will be on its own line in the GtkTextView widget. How would I do this? I'm brand new to GTK+. Here's the code sample: #include <gtk/gtk.h> typedef struct { GtkWidget *entry, *textview; } Widgets; static void insert_text (GtkButton*, Widgets*); int main (int argc, char *argv[]) { GtkWidget *window, *scrolled_win, *hbox, *vbox, *insert; Widgets *w = g_slice_new (Widgets); gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_window_set_title (GTK_WINDOW (window), "Text Iterators"); gtk_container_set_border_width (GTK_CONTAINER (window), 10); gtk_widget_set_size_request (window, -1, 200); w->textview = gtk_text_view_new (); w->entry = gtk_entry_new (); insert = gtk_button_new_with_label ("Insert Text"); g_signal_connect (G_OBJECT (insert), "clicked", G_CALLBACK (insert_text), (gpointer) w); scrolled_win = gtk_scrolled_window_new (NULL, NULL); gtk_container_add (GTK_CONTAINER (scrolled_win), w->textview); hbox = gtk_hbox_new (FALSE, 5); gtk_box_pack_start_defaults (GTK_BOX (hbox), w->entry); gtk_box_pack_start_defaults (GTK_BOX (hbox), insert); vbox = gtk_vbox_new (FALSE, 5); gtk_box_pack_start (GTK_BOX (vbox), scrolled_win, TRUE, TRUE, 0); gtk_box_pack_start (GTK_BOX (vbox), hbox, FALSE, TRUE, 0); gtk_container_add (GTK_CONTAINER (window), vbox); gtk_widget_show_all (window); gtk_main(); return 0; } /* Insert the text from the GtkEntry into the GtkTextView. */ static void insert_text (GtkButton *button, Widgets *w) { GtkTextBuffer *buffer; GtkTextMark *mark; GtkTextIter iter; const gchar *text; buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (w->textview)); text = gtk_entry_get_text (GTK_ENTRY (w->entry)); mark = gtk_text_buffer_get_insert (buffer); gtk_text_buffer_get_iter_at_mark (buffer, &iter, mark); gtk_text_buffer_insert (buffer, &iter, text, -1); } You can compile this command (assuming the file is named file.c): gcc file.c -o file `pkg-config --cflags --libs gtk+-2.0` Thanks everybody!

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  • Scanf fails with bus error

    - by Mikulas Dite
    I'm playing with C and I've run into this error: #include <stdio.h> int main () { char* foo; scanf("%s", foo); printf("entered %s", foo); return 0; } scanf takes pointer, foo is pointer, yet I get bus error. How can I make it work?

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  • Why does the task name contain "now / 30"?

    - by Jaroslav Záruba
    In the video/PDF from "Data pipelines with Google App Engine" Brett puts "now / 30" into the task name noting that he will explain the reason later, but somehow he never does. :) http://www.youtube.com/watch?v=zSDC_TU7rtc#t=41m35 task_name = '%s-%d-%d' % (sum_name, int(now / 30), index) Do you have any idea about the reason? Does it have anything to do with the 7 day period in which one can't re-use task names? URL to the session page: http://tinyurl.com/3523mej

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  • PropertyInfo from Delegate

    - by Paul Hatcherian
    Is there a simple way to get the PropertyInfo for a property in a delegate, assuming it is a simple property seletor? Example: var propertyInfo = Method<MyClass,int>(s => s.Property); ... PropertyInfo Method(Func<T1,T2> selector) { // What goes here? }

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  • Why we use "this" in Extension Methods ?

    - by M.H
    Hi, I want to ask why we use "this" keyword before the parameter in an extension method (C# Language)........... like this function : public static int ToInt(this string number) { return Int32.Parse(number); } I know that we have to use it but I don't know why.

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  • Numerical precision of double type in Visual C++ 2008 Express debugger

    - by damik
    I'm using Visual C++ 2008 Express Edition and when i debug code: double x = 0.2; I see in debugging tooltip on x 0.20000000000000001 but: typedef numeric_limits< double > double_limit; int a = double_limit::digits10 gives me: a = 15 Why results in debugger are longer than maybe ? What is this strange precision based on ? My CPU is Intel Core 2 Duo T7100

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  • Generating exactly prime number with Java

    - by Viet
    Hi, I'm aware of the function BigInteger.probablePrime(int bitLength, Random rnd) that outputs probably prime number of any bit length. I want a REAL prime number in Java. Is there any FOSS library to do so with acceptable performance? Thanks in advance!

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  • Is passing NULL param exactly the same as passing no param

    - by park
    I'm working with a function whose signature looks like this afunc(string $p1, mixed $p2, array $p3 [, int $p4 = SOM_CONST [, string $p5 ]] ) In some cases I don't have data for the last parameter $p5 to pass, but for the sake of consistency I still want to pass something like NULL. So my question, does PHP treat passing a NULL exactly the same as not passing anything? somefunc($p1, $p2, $p3, $p4 = SOM_CONST); somefunc($p1, $p2, $p3, $p4 = SOM_CONST, NULL);

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  • The Math of a Jump in a 2D game.

    - by ONi
    I have been all around with this question and I can't find the correct answer! So, behold, the description of my question: I'm working in J2ME, I have my gameloop that do the following: public void run() { Graphics g = this.getGraphics(); while (running) { long diff = System.currentTimeMillis() - lastLoop; lastLoop = System.currentTimeMillis(); input(); this.level.doLogic(); render(g, diff); try { Thread.sleep(10); } catch (InterruptedException e) { stop(e); } } } so it's just a basic gameloop, the doLogic() function calls for all the logic functions of the characters in the scene and render(g, diff) calls the animateChar function of every character on scene, following this, the animChar function in the Character class sets up everything in the screen as this: protected void animChar(long diff) { this.checkGravity(); this.move((int) ((diff * this.dx) / 1000), (int) ((diff * this.dy) / 1000)); if (this.acumFrame > this.framerate) { this.nextFrame(); this.acumFrame = 0; } else { this.acumFrame += diff; } } This ensures me that everything must to move according to the time that the machine takes to go from cycle to cycle (remember it's a phone, not a gaming rig). I'm sure it's not the most efficient way to achieve this behavior so I'm totally open for criticism of my programming skills in the comments, but here my problem: When I make I character jump, what I do is that I put his dy to a negative value, say -200 and I set the boolean jumping to true, that makes the character go up, and then I have this function called checkGravity() that ensure that everything that goes up has to go down, checkGravity also checks for the character being over platforms so I will strip it down a little for the sake of your time: public void checkGravity() { if (this.jumping) { this.jumpSpeed += 10; if (this.jumpSpeed > 0) { this.jumping = false; this.falling = true; } this.dy = this.jumpSpeed; } if (this.falling) { this.jumpSpeed += 10; if (this.jumpSpeed > 200) this.jumpSpeed = 200; this.dy = this.jumpSpeed; if (this.collidesWithPlatform()) { this.falling = false; this.standing = true; this.jumping = false; this.jumpSpeed = 0; this.dy = this.jumpSpeed; } } } So, the problem is, that this function updates the dy regardless of the diff, making the characters fly like Superman in slow machines, and I have no idea how to implement the diff factor so that when a character is jumping, his speed decrement in a proportional way to the game speed. Can anyone help me fix this issue? or give me pointers on how to make a 2D Jump in J2ME the right way. Thank you very much for your time.

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  • RenderTargetBitmap + Resource'd VisualBrush = incomplete image

    - by Will
    I've found a new twist on the "Visual to RenderTargetBitmap" question! I'm rendering previews of WPF stuff for a designer. That means I need to take a WPF visual and render it to a bitmap without that visual ever being displayed. Got a nice little method to do it like to see it here it goes private static BitmapSource CreateBitmapSource(FrameworkElement visual) { Border b = new Border { Width = visual.Width, Height = visual.Height }; b.BorderBrush = Brushes.Black; b.BorderThickness = new Thickness(1); b.Background = Brushes.White; b.Child = visual; b.Measure(new Size(b.Width, b.Height)); b.Arrange(new Rect(b.DesiredSize)); RenderTargetBitmap rtb = new RenderTargetBitmap( (int)b.ActualWidth, (int)b.ActualHeight, 96, 96, PixelFormats.Pbgra32); // intermediate step here to ensure any VisualBrushes are rendered properly DrawingVisual dv = new DrawingVisual(); using (var dc = dv.RenderOpen()) { var vb = new VisualBrush(b); dc.DrawRectangle(vb, null, new Rect(new Point(), b.DesiredSize)); } rtb.Render(dv); return rtb; } Works fine, except for one leeetle thing... if my FrameworkElement has a VisualBrush, that brush doesn't end up in the final rendered bitmap. Something like this: <UserControl.Resources> <VisualBrush x:Key="LOLgo"> <VisualBrush.Visual> <!-- blah blah --> <Grid Background="{StaticResource LOLgo}"> <!-- yadda yadda --> Everything else renders to the bitmap, but that VisualBrush just won't show. The obvious google solutions have been attempted and have failed. Even the ones that specifically mention VisualBrushes missing from RTB'd bitmaps. I have a sneaky suspicion this might be caused by the fact that its a Resource, and that lazy resource isn't being inlined. So a possible fix would be to, somehow(???), force resolution of all static resource references before rendering. But I have absolutely no idea how to do that. Anybody have a fix for this?

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  • SQLAlchemy unsupported type error - and table design issues?

    - by Az
    Hi there, back again with some more SQLAlchemy shenanigans. Let me step through this. My table is now set up as so: engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() students_table = Table('studs', metadata, Column('sid', Integer, primary_key=True), Column('name', String), Column('preferences', Integer), Column('allocated_rank', Integer), Column('allocated_project', Integer) ) metadata.create_all(engine) mapper(Student, students_table) Fairly simple, and for the most part I've been enjoying the ability to query almost any bit of information I want provided I avoid the error cases below. The class it is mapped from is: class Student(object): def __init__(self, sid, name): self.sid = sid self.name = name self.preferences = collections.defaultdict(set) self.allocated_project = None self.allocated_rank = 0 def __repr__(self): return str(self) def __str__(self): return "%s %s" %(self.sid, self.name) Explanation: preferences is basically a set of all the projects the student would prefer to be assigned. When the allocation algorithm kicks in, a student's allocated_project emerges from this preference set. Now if I try to do this: for student in students.itervalues(): session.add(student) session.commit() It throws two errors, one for the allocated_project column (seen below) and a similar error for the preferences column: sqlalchemy.exc.InterfaceError: (InterfaceError) Error binding parameter 4 - probably unsupported type. u'INSERT INTO studs (sid, name, allocated_rank, allocated_project) VALUES (?, ?, ?, ?, ?, ?, ?)' [1101, 'Muffett,M.', 1, 888 Human-spider relationships (Supervisor id: 123)] If I go back into my code I find that, when I'm copying the preferences from the given text files, it actually refers to the Project class which is mapped to a dictionary, using the unique project id's (pid) as keys. Thus, as I iterate through each student via their rank and to the preferences set, it adds not a project id, but the reference to the project id from the projects dictionary. students[sid].preferences[int(rank)].add(projects[int(pid)]) Now this is very useful to me since I can find out all I want to about a student's preferred projects without having to run another check to pull up information about the project id. The form you see in the error has the object print information passed as: return "%s %s (Supervisor id: %s)" %(self.proj_id, self.proj_name, self.proj_sup) My questions are: I'm trying to store an object in a database field aren't I? Would the correct way then, be copying the project information (project id, name, etc) into its own table, referenced by the unique project id? That way I can just have the project id field for one of the student tables just be an integer id and when I need more information, just join the tables? So and so forth for other tables? If the above makes sense, then how does one maintain the relationship with a column of information in one table which is a key index on another table? Does this boil down into a database design problem? Are there any other elegant ways of accomplishing this? Apologies if this is a very long-winded question. It's rather crucial for me to solve this, so I've tried to explain as much as I can, whilst attempting to show that I'm trying (key word here sadly) to understand what could be going wrong.

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  • Akima interpolation of an array of doubles

    - by David Rutten
    Assuming I have an array of doubles, what's a good algorithm to sample this series using Akima interpolation? I'm too stupid to translate that mathematical description into code. // values is an array of doubles // idx is the index of the left-hand value for the current interpolation // t is the normalized parameter between values[idx] and values[idx+1] // Don't worry about array bounds, I'll handle that separately. public double InterpolateAkima(double[] values, int idx, double t) { ...? }

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  • WPF how to fill combobox in data grid

    - by Rizwan Ullah
    public class DA_ActivityType { public int Id { get; set; } public string Name { get; set; } } public static List GetActivitytypes() { DataContext dbo = new DataContext(); IEnumerable activityTypes = from actType in dbo.ActivityTypes select new DA_ActivityType { Id = actType.TypeId, Name = actType.Name }; return activityTypes.ToList(); } //XAML Code

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  • how to test or describe endless possibilities?

    - by koen
    Example class in pseudocode: class SumCalculator method calculate(int1, int2) returns int What is a good way to test this? In other words how should I describe the behavior I need? test1: canDetermineSumOfTwoIntegers or test2: returnsSumOfTwoIntegers or test3: knowsFivePlusThreeIsEight Test1 and Test2 seem vague and it would need to test a specific calculation, so it doesn't really describe what is being tested. Yet test3 is very limited. What is a good way to test such classes?

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  • Variable lenght arguments in log4cxx LOG4CXX_ macros

    - by Horacio
    I am using log4cxx in a big C++ project but I really don't like how log4cxx handles multiple variables when logging: LOG4CXX_DEBUG(logger, "test " << var1 << " and " << var3 " and .....) I prefer using printf like variable length arguments: LOG4CXX_DEBUG(logger, "test %d and %d", var1, var3) So I implemented this small wrapper on top of log4cxx #include <string.h> #include <stdio.h> #include <stdarg.h> #include <log4cxx/logger.h> #include "log4cxx/basicconfigurator.h" const char * log_format(const char *fmt, ...); #define MYLOG_TRACE(logger, fmt, ...) LOG4CXX_TRACE(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_DEBUG(logger, fmt, ...) LOG4CXX_DEBUG(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_INFO(logger, fmt, ...) LOG4CXX_INFO(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_WARN(logger, fmt, ...) LOG4CXX_WARN(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_ERROR(logger, fmt, ...) LOG4CXX_ERROR(logger, log_format(fmt, ## __VA_ARGS__)) #define MYLOG_FATAL(logger, fmt, ...) LOG4CXX_FATAL(logger, log_format(fmt, ## __VA_ARGS__)) static log4cxx::LoggerPtr logger(log4cxx::Logger::getRootLogger()); int main(int argc, char **argv) { log4cxx::BasicConfigurator::configure(); MYLOG_INFO(logger, "Start "); MYLOG_WARN(logger, log_format("In running this in %d threads safe?", 1000)); MYLOG_INFO(logger, "End "); return 0; } const char *log_format(const char *fmt, ...) { va_list va; static char formatted[1024]; va_start(va, fmt); vsprintf(formatted, 1024, fmt, va); va_end(va); return formatted; } And this works perfectly but I know using that static variable (formatted) can become problematic if I start using threads and each thread logging to the same place. I am no expert in log4cxx so I was wondering if the LOG4CXX macros are handling concurrent thread access automatically? or do I have to implement some sort of locking around the log_format method? something that I wan't to avoid due to performance implications. Also I would like to ask why if I replace the vsprintf inside the log_format method with vsnprintf (that is more secure) then I get nothing printed? To compile and test this program (in Ubuntu) use : g++ -o loggertest loggertest.cpp -llog4cxx

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