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  • Make conversion to a native type explicit in C++

    - by Tal Pressman
    I'm trying to write a class that implements 64-bit ints for a compiler that doesn't support long long, to be used in existing code. Basically, I should be able to have a typedef somewhere that selects whether I want to use long long or my class, and everything else should compile and work. So, I obviously need conversion constructors from int, long, etc., and the respective conversion operators (casts) to those types. This seems to cause errors with arithmetic operators. With native types, the compiler "knows" that when operator*(int, char) is called, it should promote the char to int and call operator*(int, int) (rather than casting the int to char, for example). In my case it gets confused between the various built-in operators and the ones I created. It seems to me like if I could flag the conversion operators as explicit somehow, that it would solve the issue, but as far as I can tell the explicit keyword is only for constructors (and I can't make constructors for built-in types). So is there any way of marking the casts as explicit? Or am I barking up the wrong tree here and there's another way of solving this? Or maybe I'm just doing something else wrong...

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  • C++ return type overload hack

    - by aaa
    I was bored and came up with such hack (pseudocode): 1 struct proxy { 2 operator int(); // int function 3 operator double(); // double function 4 proxy(arguments); 5 arguments &arguments_; 6 }; 7 8 proxy function(arguments &args) { 9 return proxy(args); 10 } 11 int v = function(...); 12 double u = function(...); is it evil to use in real code?

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  • ASP.NET - How to edit 'bit' data type?

    - by Peter
    I am coding in Visual Basic. I am using a checkbox control. Now depending on its checked property I need to set/unset a bit column in a SQL Server database. Here's the code: Try conSQL.Open() Dim cmd As New SqlCommand("update Student set send_mail = " + _ sendemailCheckBox.Checked.ToString + " where student_id = '" _ + sidnolabel.Text + "'", conSQL) cmd.ExecuteNonQuery() Finally conSQL.Close() End Try The send_mail attribute is of bit datatype. This code is not working. How do I go about it?

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  • Why can I derived from a templated/generic class based on that type in C# / C++

    - by stusmith
    Title probably doesn't make a lot of sense, so I'll start with some code: class Foo : public std::vector<Foo> { }; ... Foo f; f.push_back( Foo() ); Why is this allowed by the compiler? My brain is melting at this stage, so can anyone explain whether there are any reasons you would want to do this? Unfortunately I've just seen a similar pattern in some production C# code and wondered why anyone would use this pattern.

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  • passing arg2 of 'listFind' from incompatible pointer type

    - by lego69
    Hello, I've got some problem with my function and don't know how to solve this problem, This is my code: ListResult result=listFind(currentLines, compareBasicLines, &linePrototype); <-here problem compareBasicLines pointer to function int compareBasicLines(ptrLine line1, ptrLine line2){ COMPARE_NUMBER_STRINGS(line1, line2); } COMPARE_NUMBER_STRINGS(line1, line2); defined in another file #define COMPARE_NUMBER_STRINGS(var1, var2) \ if(var1 == NULL || var2 == NULL){ \ return 0; \ } \ return strcmp(var1->strNumber, var2->strNumber); thanks in advance for everyone

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  • C++ Type error with Object versus Object reference

    - by muddybruin
    I have the following function (which worked in Visual Studio): bool Plane::contains(Vector& point){ return normalVector.dotProduct(point - position) < -doubleResolution; } When I compile it using g++ version 4.1.2 , I get the following error: Plane.cpp: In member function âvirtual bool Plane::contains(Vector&)â: Plane.cpp:36: error: no matching function for call to âVector::dotProduct(Vector)â Vector.h:19: note: candidates are: double Vector::dotProduct(Vector&) So as you can see, the compiler thinks (point-position) is a Vector but it's expecting Vector&. What's the best way to fix this? I verified that this works: Vector temp = point-position; return normalVector.dotProduct(temp) < -doubleResolution; But I was hoping for something a little bit cleaner. I heard a suggestion that adding a copy constructor might help. So I added a copy constructor to Vector (see below), but it didn't help. Vector.h: Vector(const Vector& other); Vector.cpp: Vector::Vector(const Vector& other) :x(other.x), y(other.y), z(other.z), homogenous(other.homogenous) { }

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  • 9gag type of website

    - by awtasdfas
    for something like www.9gag.com , which open source mvc framework can be used? in particular the main page, with highly rated content is what i am looking for.. along with an option for users to thumbs up/heart every article/post/blog/vlog/podcast/link.

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  • Java generics - getting the type..

    - by peter
    Hi! I'm a c# guy giving Java a try .. so how would I do the following in java. in C# public T create_an_instance_of<T>(){ T instance = default (T); // here's usually some factory to create the implementation instance = some_factory.build<T>(); // or even.. instance = some_factory.build(typeOf(T) ); return instance; }

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  • Fastest way to compare Objects of type DateTime

    - by radbyx
    I made this. Is this the fastest way to find lastest DateTime of my collection of DateTimes? I'm wondering if there is a method for what i'm doing inside the foreach, but even if there is, I can't see how it can be faster than what i all ready got. List<StateLog> stateLogs = db.StateLog.Where(p => p.ProductID == product.ProductID).ToList(); DateTime lastTimeStamp = DateTime.MinValue; foreach (var stateLog in stateLogs) { int result = DateTime.Compare(lastTimeStamp, stateLog.TimeStamp); if (result < 0) lastTimeStamp = stateLog.TimeStamp; // sæt fordi timestamp er senere }

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  • type casting in mysql

    - by muralikalpana
    i have passportno(varchar) in database. i am entering values like this 001,002,003. and i want to display like sorting order. now i wrote query like this "select * from passport_registration where status=1 ORDER BY passportno" then displaying output like this......077,088,099,100,1000,1001,1009,101,1010 i want to diplay sort order. how to do?

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  • C# newbie problem with variable types

    - by ile
    int newWidth = 100; int newHeight = 100; double ratio = 0; if (img1.Width > img1.Height) { ratio = img1.Width / img1.Height; newHeight = (int)(newHeight / ratio); } else { ratio = img1.Height / img1.Width; newWidth = (int)(newWidth / ratio); } Image bmp1 = img1.GetThumbnailImage(newWidth, newHeight, null, IntPtr.Zero); bmp1.Save(Server.MapPath("~/Uploads/Photos/Thumbnails/") + photo.PhotoID + ".jpg"); I always get Image with both height and width having same values (100) I am obiously doing something wrong with type conversion?

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  • Using RedirectToAction with custom type parameter

    - by user170497
    Hi asp.net mvc 2 I have this action in Identity controller public ActionResult Details(string id, MessageUi message) { And I'm trying to redirect to this action from another controller, but I don't know how should I pass the message parameter I was trying with var id = "someidvalue" var message = new MessageUi("somevalue"); return RedirectToAction("Details", "Identity", new { id, message}); } but message parameter is null

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  • enum type in C++

    - by httpinterpret
    This works: enum TPriority { EPriorityIdle = -100, EPriorityLow = -20, EPriorityStandard = 0, EPriorityUserInput = 10, EPriorityHigh = 20 }; TPriority priority = EPriorityIdle; But this doesn't work: TPriority priority = -100; Any reason?

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  • MVC Display Template for Generic Type

    - by Kyle
    I am trying to use the model ListModel as a generic list model. I would like to enter on the page @Html.DisplayForModel() However the MVC is not correctly finding the templated file "ListModel.cshtml". It must work differently for generic models. What should I name the templated file in order for it to correctly be located? public class ListModel<T> { public IEnumerable<T> Models {get;set;} public string NextPage {get;set;} } I would expect it to look for "Shared/DisplayTemplates/ListModel.ascx" but it doesn't. Does anyone know?

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  • Testing variable types in Python

    - by Jasper
    Hello, I'm creating an initialising function for the class 'Room', and found that the program wouldn't accept the tests I was doing on the input variables. Why is this? def __init__(self, code, name, type, size, description, objects, exits): self.code = code self.name = name self.type = type self.size = size self.description = description self.objects = objects self.exits = exits #Check for input errors: if type(self.code) != type(str()): print 'Error found in module rooms.py!' print 'Error number: 110' elif type(self.name) != type(str()): print 'Error found in module rooms.py!' print 'Error number: 111' elif type(self.type) != type(str()): print 'Error found in module rooms.py!' print 'Error number: 112' elif type(self.size) != type(int()): print 'Error found in module rooms.py!' print 'Error number: 113' elif type(self.description) != type(str()): print 'Error found in module rooms.py!' print 'Error number: 114' elif type(self.objects) != type(list()): print 'Error found in module rooms.py!' print 'Error number: 115' elif type(self.exits) != type(tuple()): print 'Error found in module rooms.py!' print 'Error number: 116' When I run this I get this error: Traceback (most recent call last): File "/Users/Jasper/Development/Programming/MyProjects/Game Making Challenge/Europa I/rooms.py", line 148, in <module> myRoom = Room(101, 'myRoom', 'Basic Room', 5, '<insert description>', myObjects, myExits) File "/Users/Jasper/Development/Programming/MyProjects/Game Making Challenge/Europa I/rooms.py", line 29, in __init__ if type(self.code) != type(str()): TypeError: 'str' object is not callable

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  • Scala Unit type

    - by portoalet
    I use opencsv to parse csv files, and my code is while( (line = reader.readNext()) != null ) { .... } I got a compiler warning saying: comparing values of types Unit and Null using `!=' will always yield true [warn] while( (aLine = reader.readNext()) != null ) { How should I do the while loop?

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