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  • Why does casting a NaN to a long yeild a valid result?

    - by brainimus
    In the sample code below I am dividing by zero which when I step through it with the debugger the (dividend / divisor) yeilds an Infinity or NaN (if the divisor is zero). When I cast this result to a long I get a valid result, usually something like -9223372036854775808. Why is this cast valid? Why doesn't it stop executing (throw an exception for example) rather than assign an arbitrary value? double divisor = 0; double dividend = 7; long result = (long)(dividend / divisor);

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  • JNI AttachCurrentThread NULLs the jenv

    - by Damg
    Hello all, I'm currently in the process of adding JNI functionality into a legacy delphi app. In a single-threaded environment everything works fine, but as soon as I move into multi-threaded environment, things start to become hairy. My problem is that calling JavaVM^.AttachCurrentThread( JavaVM, @JEnv, nil ); returns 0, but puts the JEnv pointer to nil. I have no idea why jvm.dll should return a NULL pointer. Is there anything I am missing? Thank you in advance -- damg PS: * Environment: WinXP + JDK 1.6 * Using JNI.pas from http://www.pacifier.com/~mmead/jni/delphi/

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  • Should downcasting be avoided while using a class hierarchy in C++?

    - by neuviemeporte
    Let's say I'm writing an application which works with projects, and exposes different functionality depending on the type of the project. I have a hierarchy of classes for the different types of projects: class AbstractProject { }; class ProjectA : public AbstractProject { }; class ProjectB : public AbstractProject { }; class ProjectC : public AbstractProject { }; Now, I was planning to have an AbstractProject *_currentProject pointer as a member in the application's main class, pop up a dialog box on startup and based on the selection, do: _currentProject = new ProjectB(); // e.g. Later, I'll have to downcast the pointer to the specific type to utilize the functionality specific to different Project-s. Somehow this makes me feel uneasy. Is there a Better Way of doing this?

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  • Inheritance - initialization problem

    - by dumbquestion
    I have a c++ class derived from a base class in a framework. The derived class doesn't have any data members because I need it to be freely convertible into a base class and back - the framework is responsible for loading and saving the objects and I can't change it. My derived class just has functions for accessing the data. But there are a couple of places where I need to store some temporary local variables to speed up access to data in the base class. mydata* MyClass::getData() { if ( !m_mydata ) { // set to NULL in the constructor m_mydata = some_long_and complex_operation_to_get_the_data_in_the_base() } return m_mydata; } The problem is if I just access the object by casting the base class pointer returned from the framework to MyClass* the ctor for MyClass is never called and m_mydata is junk. Is there a way of only initializing the m_mydata pointer once?

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  • measuring uncertainty in matlabs svmclassify

    - by Mark
    I'm doing contextual object recognition and I need a prior for my observations. e.g. this space was labeled "dog", what's the probability that it was labeled correctly? Do you know if matlabs svmclassify has an argument to return this level of certainty with it's classification? If not, matlabs svm has the following structures in it: SVM = SupportVectors: [11x124 single] Alpha: [11x1 double] Bias: 0.0915 KernelFunction: @linear_kernel KernelFunctionArgs: {} GroupNames: {11x1 cell} SupportVectorIndices: [11x1 double] ScaleData: [1x1 struct] FigureHandles: [] Can you think of any ways to compute a good measure of uncertainty from these? (Which support vector to use?) Papers/articles explaining uncertainty in SVMs welcome. More in depth explanations of matlabs SVM are also welcome. If you can't do it this way, can you think of any other libraries with SVMs that have this measure of uncertainty?

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  • Rounding a positive number to a power of another number

    - by Sagekilla
    I'm trying to round a number to the next smallest power of another number. The number I'm trying to round is always positive. I'm not particular on which direction it rounds, but I prefer downwards if possible. I would like to be able to round towards arbitrary bases, but the ones I'm most concerned with at the moment is base 2 and fractional powers of 2 like 2^(1/2), 2^(1/4), and so forth. Here's my current algorithm for base 2. The log2 I multiply by is actually the inverse of log2: double roundBaseTwo(double x) { return 1.0 / (1 << (int)((log(x) * log2)) } Any help would be appreciated!

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  • .Net Round-trip Types

    - by Fujiy
    I making a method that generate a unique string key for some parameters. But the same key if call with same values. I just accept primitive types, string, DateTime, Guid, and Nullable(since I append types together, I can distinguish who is int and who is int?), because I can convert all to string without lost values or precision.(for float and double a use ToString("R"), to DateTime ToString("O")). Exists a easy way to know which types I can transform in strings without conflict? And how do this transform(how I said before, float, double and datetime have specific ways) Thanks

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  • Strange difference between optimized/non optimized microsoft c++ code

    - by Anders Forsgren
    I have a c++ program with a method that looks something like this: int myMethod(int* arr1, int* arr2, int* index) { arr1--; arr2--; int val = arr1[*index]; int val2 = arr2[val]; doMoreThings(val); } With optimizations enabled (/O2) the first line where the first pointer is decremented is not executed. I assume the compiler believes that the arr1 array is not used since it thinks it can remove the decrement. Am I violating some convention in the above code? What could cause this behavior? It is a very old piece of f2c-translated code, the pointer decrement is due to the 1-based indexing of the original code.

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  • How to use the boost lexical_cast library for just for checking input

    - by Inverse
    I use the boost lexical_cast library for parsing text data into numeric values quite often. In several situations however, I only need to check if values are numeric; I don't actually need or use the conversion. So, I was thinking about writing a simple function to test if a string is a double: template<typename T> bool is_double(const T& s) { try { boost::lexical_cast<double>(s); return true; } catch (...) { return false; } } My question is, are there any optimizing compilers that would drop out the lexical_cast here since I never actually use the value? Is there a better technique to use the lexical_cast library to perform input checking?

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  • How can i use listDictionary?

    - by Phsika
    i can fill my listdictinary but, if running error returns to me in " foreach (string ky in ld.Keys)"(invalid operation Exception was unhandled) Error Detail : After creating a pointer to the list of sample collection has been changed. C# ListDictionary ld = new ListDictionary(); foreach (DataColumn dc in dTable.Columns) { MessageBox.Show(dTable.Rows[0][dc].ToString()); ld.Add(dc.ColumnName, dTable.Rows[0][dc].ToString()); } foreach (string ky in ld.Keys) if (int.TryParse(ld[ky].ToString(), out QuantityInt)) ld[ky] = "integer"; else if(double.TryParse(ld[ky].ToString(), out QuantityDouble)) ld[ky]="double"; else ld[ky]="nvarchar";

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  • What's wrong with this addProximity code?

    - by Pentium10
    I have this code: private void setupProximity() { Intent intent = new Intent(this, viewContacts.class); PendingIntent sender = PendingIntent.getBroadcast(this, 0, intent, 0); LocationUtils.addProximity(this, -37.40, 144.55, 1000, 1000000, sender); } public static void addProximity(Context ctx,double lat, double lon, float rad,long exp, PendingIntent pintent) { LocationManager lm = (LocationManager) ctx.getSystemService(Context.LOCATION_SERVICE); lm.addProximityAlert(lat, lon, rad, exp, pintent); } Why I don't get the class to fire up? I am in the range of the zone.

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  • Matrix multiplication using Matrix Template library (MTL 4)

    - by Lxc
    The program is as following: #include <iostream> #include <boost/numeric/mtl/mtl.hpp> using namespace mtl; int main(int argc, char* argv[]) { dense_vector<double> a(5,1.0); dense_vector<double> b(5,2.0); a * trans(b); } I want to calculate a * trans(b), but there is a compling error :C2893. Will someone help me? Thanks a lot!

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  • Avoid Flickering in Windows Forms?

    - by user1733909
    Double buffering not working with combo-box. is there any another methods to avoid flickering in windows forms? i have one windows form with number of panels in it. I'm showing only one panel at a time based on my menu selection. i have one icon panel,one header panel and the combo box. based on the selected item of that combo-box the gridview1 and 2 are filling. when I'm rapidly selecting the combo-box item using my keyboard down arrow the icon panel and the header panel are always repainting. i need to keep that both without any change. this two panels producing some flashing effect(ie,they are blinking or flashing) while I'm changing the combo box selected index. is there any way to avoid this flashing.? i tried double-buffered enabled in form constructor and form load event. Please Help..............

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  • Does C++ require a destructor call for each placement new?

    - by Josh Haberman
    I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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  • C++ integer floor function

    - by Thomas
    I want to implement greatest integer function. int x = 5/3; My question is with greater numbers could there be a loss of precision as 5/3 would produce a double? EDIT: Greatest integer function is integer less than or equal to X. Example: 4.5 = 4 4 = 4 3.2 = 3 3 = 3 What I want to know is 5/3 going to produce a double? Because if so I will have loss of precision when converting to int. Hope this makes sense. RE-EDIT: What OP calls 'greatest integer' most of us call 'floor'.

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  • Can I control the mouse cursor from within R?

    - by Bernd Meyer
    Is it possible, to control the mouse pointer from the R console? I have something like this in mind: move_mouse(x_pos=100,y_pos=200) # move the mouse pointer to position (100,200) mouse_left_button_down # simulate a press of the left button move_mouse(x_pos=120,y_pos=250) # move mouse to select something mose_release_left_button # release the pressed button In MATLAB, something like this is possible with the following code import java.awt.Robot; mouse = Robot; mouse.mouseMove(0, 0); mouse.mouseMove(100, 200); Is something similar possible for the keybord? E.g. simulate keybord events?

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  • Why does OpenGL's glDrawArrays() fail with GL_INVALID_OPERATION under Core Profile 3.2, but not 3.3 or 4.2?

    - by metaleap
    I have OpenGL rendering code calling glDrawArrays that works flawlessly when the OpenGL context is (automatically / implicitly obtained) 4.2 but fails consistently (GL_INVALID_OPERATION) with an explicitly requested OpenGL core context 3.2. (Shaders are always set to #version 150 in both cases but that's beside the point here I suspect.) According to specs, there are only two instances when glDrawArrays() fails with GL_INVALID_OPERATION: "if a non-zero buffer object name is bound to an enabled array and the buffer object's data store is currently mapped" -- I'm not doing any buffer mapping at this point "if a geometry shader is active and mode? is incompatible with [...]" -- nope, no geometry shaders as of now. Furthermore: I have verified & double-checked that it's only the glDrawArrays() calls failing. Also double-checked that all arguments passed to glDrawArrays() are identical under both GL versions, buffer bindings too. This happens across 3 different nvidia GPUs and 2 different OSes (Win7 and OSX, both 64-bit -- of course, in OSX we have only the 3.2 context, no 4.2 anyway). It does not happen with an integrated "Intel HD" GPU but for that one, I only get an automatic implicit 3.3 context (trying to explicitly force a 3.2 core profile with this GPU via GLFW here fails the window creation but that's an entirely different issue...) For what it's worth, here's the relevant routine excerpted from the render loop, in Golang: func (me *TMesh) render () { curMesh = me curTechnique.OnRenderMesh() gl.BindBuffer(gl.ARRAY_BUFFER, me.glVertBuf) if me.glElemBuf > 0 { gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, me.glElemBuf) gl.VertexAttribPointer(curProg.AttrLocs["aPos"], 3, gl.FLOAT, gl.FALSE, 0, gl.Pointer(nil)) gl.DrawElements(me.glMode, me.glNumIndices, gl.UNSIGNED_INT, gl.Pointer(nil)) gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, 0) } else { gl.VertexAttribPointer(curProg.AttrLocs["aPos"], 3, gl.FLOAT, gl.FALSE, 0, gl.Pointer(nil)) /* BOOM! */ gl.DrawArrays(me.glMode, 0, me.glNumVerts) } gl.BindBuffer(gl.ARRAY_BUFFER, 0) } So of course this is part of a bigger render-loop, though the whole "*TMesh" construction for now is just two instances, one a simple cube and the other a simple pyramid. What matters is that the entire drawing loop works flawlessly with no errors reported when GL is queried for errors under both 3.3 and 4.2, yet on 3 nvidia GPUs with an explicit 3.2 core profile fails with an error code that according to spec is only invoked in two specific situations, none of which as far as I can tell apply here. What could be wrong here? Have you ever run into this? Any ideas what I have been missing?

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  • How to access the map returned by IParameterValues::getParameterValues()?

    - by Hua
    I declared a command and a commandParameter for this command. I specified the "values" of this commandParameter as a class implemented by myself. The implementation of this class is below, public class ParameterValues implements IParameterValues { @Override public Map<String, Double> getParameterValues() { // TODO Auto-generated method stub Map<String, Double> values = new HashMap<String, Double>(2); values.put("testParam", 1.1239); values.put("AnotherTest", 4.1239); return values; } } The implementation of the handler of this command is blow, public class testHandler extends AbstractHandler implements IHandler { private static String PARAMETER_ID = "my.parameter1"; @Override public Object execute(ExecutionEvent event) throws ExecutionException { String value = event.getParameter(PARAMETER_ID); MessageDialog.openInformation(HandlerUtil.getActiveShell(event), "Test", "Parameter ID: " + PARAMETER_ID + "\nValue: " + value); return null; } } Now, I contribute the command to a menu, <menuContribution locationURI="menu:org.eclipse.ui.main.menu"> <menu id="my.edit" label="Edit"> <command commandId="myCommand.test" label="Test1"> <parameter name="my.parameter1" value="testParam"> </parameter> </command> Since I specified a "values" class for the commandParater, I expect when the menu is clicked, this code line "String value = event.getParameter(PARAMETER_ID);" in the handler class returns 1.1239 instead of "testParam". But, I still see that code line returns "testParam". What's the problem? How could I access the map returned by getParameterValues()? By the way, following menu declaration still works even I don't define "ppp" in the map. <menuContribution locationURI="menu:org.eclipse.ui.main.menu"> <menu id="my.edit" label="Edit"> <command commandId="myCommand.test" label="Test1"> <parameter name="my.parameter1" value="ppp"> </parameter> </command> Thanks!

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  • Regarding C typedef struct

    - by Bruce Duncan
    I have multiple instances of typedef struct box so box box1, box box2 etc. The members of the struct are length, width, height etc. typedef struct { int width; int height; } box; box box1; box box2; How can I create a function that operates on all the width members of each box instance? My confusion is how do I pass a pointer to a typedef struct member that works across all instances of box. I know how to pass a pointer to a specific instance member like box1.width but how to pass .width and then do box1.width=value; box2.width=value; box3.width=value; within the function?

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  • c# im getting an error

    - by vj4u
    double dval = 1; for (int i = 0; i < Cols; i++) { k = 0; dval = 1; for (int j = Cols - 1; j >= 0; j--) { colIndex = (i + j) % 3; val *= dval[colIndex, k]; k++; } det -= dval; } im getting an error Cannot apply indexing with [] to an expression of type 'double' for dval help its urgent

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  • What object called a method in Obj-C

    - by Loz
    Hi, I am looking to write a plugin controller in Cocoa that loads bundles, and exposes a specific set of methods for the plugins to call. My question is this: is it possible to know (any) info about the object that called a method in the controller. When an instantiated plugin calls a method in my plugin controller, I would like to know which of the plugin instances called the method, without having to rely on the plugin sending a pointer to itself as a parameter (I could always validate the pointer they send, but I want to keep the API methods as simple as possible). There may be no perfect solution (and there are simple workarounds), but it's always good to learn some new tricks if possible (or the reasons why it's impossible). Thanks in advance.

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  • allocator with no template

    - by Merni
    Every stl container take an allocator as a second object, template < class T, class Allocator = allocator<T> > class vector; If you write your own class It is possible to use your own allocator. But is it possible to write your own allocator without using templates? For example, writing this function is not easy if you are not allowed to use templates pointer allocate(size_type n, const_pointer = 0) { void* p = std::malloc(n * sizeof(T)); if (!p) throw std::bad_alloc(); return static_cast<pointer>(p); } Because how could you know the size of T?

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  • is there a way to remove duplication in this code

    - by oo
    i have a method that looks like this: private double GetX() { if (Servings.Count > 0) { return Servings[0].X; } if (!string.IsNullOrEmpty(Description)) { FoodDescriptionParser parser = new FoodDescriptionParser(); return parser.Parse(Description).X; } return 0; } and i have another method that looks like this: private double GetY() { if (Servings.Count > 0) { return Servings[0].Y; } if (!string.IsNullOrEmpty(Description)) { FoodDescriptionParser parser = new FoodDescriptionParser(); return parser.Parse(Description).Y; } return 0; } is there anyway to consolidate this as the only thing different is the property names?

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