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  • Operator overloading C++ outside class

    - by bobobobo
    Well, so there are 2 ways to overload operators for a C++ class INSIDE CLASS class Vector2 { public: float x, y ; Vector2 operator+( const Vector2 & other ) { Vector2 ans ; ans.x = x + other.x ; ans.y = y + other.y ; return ans ; } } ; OUTSIDE CLASS class Vector2 { public: float x, y ; } ; Vector2 operator+( const Vector2& v1, const Vector2& v2 ) { Vector2 ans ; ans.x = v1.x + v2.x ; ans.y = v1.y + v2.y ; return ans ; } In C# apparently you can only use the OUTSIDE class method The question is, in C++, which is "morer-correcter?" Which is preferable? When is one way better than another?

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  • null coalescing operator for javascript?

    - by Daniel Schaffer
    I assumed this question has already been asked here, but I couldn't find any, so here it goes: Is there a null coalescing operator in Javascript? For example, in C#, I can do this: String someString = null; var whatIWant = someString ?? "Cookies!"; The best approximation I can figure out for Javascript is using the conditional operator: var someString = null; var whatIWant = someString ? someString : 'Cookies!'; Which is sorta icky IMHO. Can I do better?

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  • Using string constants in implicit conversion

    - by kornelijepetak
    Consider the following code: public class TextType { public TextType(String text) { underlyingString = text; } public static implicit operator String(TextType text) { return text.underlyingString; } private String underlyingString; } TextType text = new TextType("Something"); String str = text; // This is OK. But I want to be able do the following, if possible. TextType textFromStringConstant = "SomeOtherText"; I can't extend the String class with the TextType implicit operator overload, but is there any way to assign a literal string to another class (which is handled by a method or something)? String is a reference type so when they developed C# they obviously had to use some way to get a string literal to the class. I just hope it's not hardcoded into the language.

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  • no match for operator= using a std::vector

    - by Max
    I've got a class declared like this: class Level { private: std::vector<mapObject::MapObject> features; (...) }; and in one of its member functions I try to iterate through that vector like this: vector<mapObject::MapObject::iterator it; for(it=features.begin(); it<features.end(); it++) { /* loop code */ } This seems straightforward to me, but g++ gives me this error: src/Level.cpp:402: error: no match for ‘operator=’ in ‘it = ((const yarl::level::Level*)this)-yarl::level::Level::features.std::vector<_Tp, _Alloc::begin [with _Tp = yarl::mapObject::MapObject, _Alloc = std::allocator<yarl::mapObject::MapObject>]()’ /usr/include/c++/4.4/bits/stl_iterator.h:669: note: candidates are: __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*,std::vector & __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*,std::vector >::operator=(const __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*, ``std::vector<yarl::mapObject::MapObject, std::allocator<yarl::mapObject::MapObject> > >&) Anyone know why this is happening?

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  • Problem with operator ==

    - by CPPDev
    I am facing some problem with use of operator == in the following c++ program. #include < iostream> using namespace std; class A { public: A(char *b) { a = b; } A(A &c) { a = c.a; } bool operator ==(A &other) { return strcmp(a, other.a); } private: char *a; }; int main() { A obj("test"); A obj1("test1"); if(obj1 == A("test1")) { cout<<"This is true"<<endl; } } What's wrong with if(obj1 == A("test1")) line ?? Any help is appreciated.

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  • C++ overloading operator comma for variadic arguments

    - by uray
    is it possible to construct variadic arguments for function by overloading operator comma of the argument? i want to see an example how to do so.., maybe something like this: template <typename T> class ArgList { public: ArgList(const T& a); ArgList<T>& operator,(const T& a,const T& b); } //declaration void myFunction(ArgList<int> list); //in use: myFunction(1,2,3,4); //or maybe: myFunction(ArgList<int>(1),2,3,4);

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  • Can't find which row is causing conversion error

    - by Marwan
    I have the following table: CREATE TABLE [dbo].[Accounts1]( [AccountId] [nvarchar](50) NULL, [ExpiryDate] [nvarchar](50) NULL ) I am trying to convert nvarchar to datetime using this query: select convert(datetime, expirydate) from accounts I get this error: Conversion failed when converting datetime from character string. The status bar says "2390 rows". I go to rows 2390, 2391 and 2392. There is nothing wrong with the data there. I even try to convert those particular rows and it works. How can I find out which row(s) is causing the conversion error?

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  • C# String Operator Overloading

    - by ScottSEA
    G'Day Mates - What is the right way (excluding the argument of whether it is advisable) to overload the string operators <, , <= and = ? I've tried it five ways to Sunday and I get various errors - my best shot was declaring a partial class and overloading from there, but it won't work for some reason. namespace System { public partial class String { public static Boolean operator <(String a, String b) { return a.CompareTo(b) < 0; } public static Boolean operator >(String a, String b) { return a.CompareTo(b) > 0; } } }

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  • An operator == whose parameters are non-const references

    - by Eduardo León
    I this post, I've seen this: class MonitorObjectString: public MonitorObject { // some other declarations friend inline bool operator==(/*const*/ MonitorObjectString& lhs, /*const*/ MonitorObjectString& rhs) { return lhs.fVal==rhs.fVal; } } Before we can continue, THIS IS VERY IMPORTANT: I am not questioning anyone's ability to code. I am just wondering why someone would need non-const references in a comparison. The poster of that question did not write that code. This was just in case. This is important too: I added both /*const*/s and reformatted the code. Now, we get back to the topic: I can't think of a sane use of the equality operator that lets you modify its by-ref arguments. Do you?

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  • Undetermined type conversion in VB.NET 2008

    - by user337501
    I figured this would be a quick google, but extensive searching hasnt yielded any results. Everything about type conversion seems to dance around this concept. I want to get the type of variable "a", and make a new variable named "b" of that type. Otherwise I could have "a" as a type already declared and "b" simply as an Object, then try to cast "b" to the type of "a". Dim a As Integer Dim b As Whatever a Is OR TryCast(b, Whatever a Is) I would also like to make the conversion using a variable representation of the type, but cant find info on how to do that either. Sorta like: Dim a As Integer Dim b As Object Dim t As Type t = a.GetType() TryCast(b, t) Realizing I'm completely misusing TryCast here, I'm mostly trying to get my goal across. I figured it would be an easy quick thing to do but I cant really find any specific info on it. Any ideas?

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  • Data loss between conversion

    - by Alex Brooks
    Why is it that I loose data between the conversions below even though both types take up the same amount of space? If the conversion was done bitwise, it should be true that x = z unless data is being stripped during the conversion, right? Is there a way to do the two conversions without losing data (i.e. so that x = z)? main.cpp: #include <stdio.h> #include <stdint.h> int main() { double x = 5.5; uint64_t y = static_cast<uint64_t>(x); double z = static_cast<double>(y) // Desire : z = 5.5; printf("Size of double: %lu\nSize of uint64_t: %lu\n", sizeof(double), sizeof(uint64_t)); printf("%f\n%lu\n%f\n", x, y, z); } Results: Size of double: 8 Size of uint64_t: 8 5.500000 5 5.000000

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  • Dynamic Operator Overloading on dict classes in Python

    - by Ishpeck
    I have a class that dynamically overloads basic arithmetic operators like so... import operator class IshyNum: def __init__(self, n): self.num=n self.buildArith() def arithmetic(self, other, o): return o(self.num, other) def buildArith(self): map(lambda o: setattr(self, "__%s__"%o,lambda f: self.arithmetic(f, getattr(operator, o))), ["add", "sub", "mul", "div"]) if __name__=="__main__": number=IshyNum(5) print number+5 print number/2 print number*3 print number-3 But if I change the class to inherit from the dictionary (class IshyNum(dict):) it doesn't work. I need to explicitly def __add__(self, other) or whatever in order for this to work. Why?

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  • Easy way for Crystal Reports to MS SQL Server Reporting Services conversion

    - by scoob
    Is there a way to easily convert Crystal Reports reports to Reporting Services RDL format? We have quite a few reports that will be needing conversion soon. I know about the manual process (which is basically rebuilding all your reports from scratch in SSRS), but my searches pointed to a few possibilities with automatic conversion "acceleration" with several consulting firms. (As described on http://www.microsoft.com/sql/technologies/reporting/partners/crystal-migration.mspx). Do any of you have any valid experiences or recomendations regarding this particular issue? Are there any tools around that I do not know about?

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  • Scala :: operator, how it works?

    - by Felix
    Hello Guys, in Scala, I can make a caseclass case class Foo(x:Int) and then put it in a list like so: List(Foo(42)) Now, nothing strange here. The following is strange to me. The operator :: is a function on a list, right? With any function with 1 argument in Scala, I can call it with infix notation. An example is 1 + 2 is a function (+) on the object Int. The class Foo I just defined does not have the :: operator, so how is the following possible: Foo(40) :: List(Foo(2)) ? In scala 2.8 rc1, I get the following output from the interactive prompt: scala> case class Foo(x:Int) defined class Foo scala> Foo(40) :: List(Foo(2)) res2: List[Foo] = List(Foo(40), Foo(2)) scala> I can go on and use it, but if someone can explain it I will be glad :)

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  • Passing operator as a parameter

    - by nacho4d
    Hi, I want to have a function that evaluates 2 bool vars (like a truth table) for example: since T | F : T then myfunc('t', 'f', ||); /*defined as: bool myfunc(char lv, char rv, ????)*/ should return true; how can I pass the third parameter? (I know is possible to pass it as a char* but then I will have to have another table to compare operator string and then do the operation which is something I would like to avoid) Is it possible to pass an operator like ^(XOR) or ||(OR) or &&(AND), etc in a function/method? Thanks in advance

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  • copy C'tor with operator= | C++

    - by user2266935
    I've got this code here: class DerivedClass : public BaseClass { SomeClass* a1; Someclass* a2; public: //constructors go here ~DerivedClass() { delete a1; delete a2;} // other functions go here .... }; My first question is as follows: Can I write an "operator=" to "DerivedClass" ? (if your answer is yes, could you show me how?) My second question is: If the answer to the above is yes, could you show me how to make an "copy c'tor" using the "operator=" that you wrote beforehand (if that is even possible)? Your help would be much appreciated !

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  • template; operator (int)

    - by Oops
    Hi, regarding my Point struct already mentioned here: http://stackoverflow.com/questions/2794369/template-class-ctor-against-function-new-c-standard is there a chance to replace the function toint() with a cast-operator (int)? namespace point { template < unsigned int dims, typename T > struct Point { T X[ dims ]; //umm??? template < typename U > Point< dims, U > operator U() const { Point< dims, U > ret; std::copy( X, X + dims, ret.X ); return ret; } //umm??? Point< dims, int > operator int() const { Point<dims, int> ret; std::copy( X, X + dims, ret.X ); return ret; } //OK Point<dims, int> toint() { Point<dims, int> ret; std::copy( X, X + dims, ret.X ); return ret; } }; //struct Point template < typename T > Point< 2, T > Create( T X0, T X1 ) { Point< 2, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; return ret; } }; //namespace point int main(void) { using namespace point; Point< 2, double > p2d = point::Create( 12.3, 34.5 ); Point< 2, int > p2i = (int)p2d; //äähhm??? std::cout << p2d.str() << std::endl; char c; std::cin >> c; return 0; } I think the problem is here that C++ cannot distinguish between different return types? many thanks in advance. regards Oops

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  • Should I convert my AAC M4A files to MP3?

    - by j0rd4n
    Due to Apple, I have a large majority of my music files in the AAC M4A format. They do NOT have DRM so I don't have to worry about that. I'm getting tired of Apple products and really want to switch to a different brand player (and something more compatible with Linux). It appears most MP3 players support...well...MP3 and not AAC. Should I convert my library to be free of Apple and open to other players? Is this a lossless conversion? Can it be lossless? If I will lose quality, I'm not interested. Am I even doing the right thing? AAC is the better format, but I'm not seeing a lot of support for it yet. I'll be honest and say that I need some education in this department. Any helpful advice is most welcome.

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  • null-coalescing operator or conditional operator

    - by rkrauter
    Which coding style do you prefer: object o = new object(); //string s1 = o ?? "Tom"; // Cannot implicitly convert type 'object' to 'string' CS0266 string s3 = Convert.ToString(o ?? "Tom"); string s2 = (o != null) ? o.ToString() : "Tom"; s2 or s3? Is it possible to make it shorter? s1 does not obviously work.

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  • Working with Reporting Services Filters – Part 2: The LIKE Operator

    - by smisner
    In the first post of this series, I introduced the use of filters within the report rather than in the query. I included a list of filter operators, and then focused on the use of the IN operator. As I mentioned in the previous post, the use of some of these operators is not obvious, so I'm going to spend some time explaining them as well as describing ways that you can use report filters in Reporting Services in this series of blog posts. Now let's look at the LIKE operator. If you write T-SQL queries, you've undoubtedly used the LIKE operator to produce a query using the % symbol as a wildcard for multiple characters like this: select * from DimProduct where EnglishProductName like '%Silver%' And you know that you can use the _ symbol as a wildcard for a single character like this: select * from DimProduct where EnglishProductName like '_L Mountain Frame - Black, 4_'   So when you encounter the LIKE operator in a Reporting Services filter, you probably expect it to work the same way. But it doesn't. You use the * symbol as a wildcard for multiple characters as shown here: Expression Data Type Operator Value [EnglishProductName] Text Like *Silver* Note that you don’t have to include quotes around the string that you use for comparison. Books Online has an example of using the % symbol as a wildcard for a single character, but I have not been able to successfully use this wildcard. If anyone has a working example, I’d love to see it!

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  • Which to use - "operator new" or "operator new[]" - to allocate a block of raw memory in C++?

    - by sharptooth
    My C++ program needs a block of uninitialized memory. In C I would use malloc() and later free(). In C++ I can either call ::operator new or ::operator new[] and ::operator delete or operator delete[] respectively later. Looks like both ::operator new and ::operator new[] have exactly the same signature and exactly the same behavior. The same for ::operator delete and ::operator delete[]. The only thing I shouldn't do is pairing operator new with operator delete[] and vice versa - undefined behavior. Other than that which pair do I choose and why?

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  • C++ operator new, object versions, and the allocation sizes

    - by mizubasho
    Hi. I have a question about different versions of an object, their sizes, and allocation. The platform is Solaris 8 (and higher). Let's say we have programs A, B, and C that all link to a shared library D. Some class is defined in the library D, let's call it 'classD', and assume the size is 100 bytes. Now, we want to add a few members to classD for the next version of program A, without affecting existing binaries B or C. The new size will be, say, 120 bytes. We want program A to use the new definition of classD (120 bytes), while programs B and C continue to use the old definition of classD (100 bytes). A, B, and C all use the operator "new" to create instances of D. The question is, when does the operator "new" know the amount of memory to allocate? Compile time or run time? One thing I am afraid of is, programs B and C expect classD to be and alloate 100 bytes whereas the new shared library D requires 120 bytes for classD, and this inconsistency may cause memory corruption in programs B and C if I link them with the new library D. In other words, the area for extra 20 bytes that the new classD require may be allocated to some other variables by program B and C. Is this assumption correct? Thanks for your help.

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  • Reflection and Operator Overloads in C#

    - by TenshiNoK
    Here's the deal. I've got a program that will load a given assembly, parse through all Types and their Members and compile a TreeView (very similar to old MSDN site) and then build HTML pages for each node in the TreeView. It basically takes a given assembly and allows the user to create their own MSDN-like library for it for documentation purposes. Here's the problem I've run into: whenever an operator overload is encounted in a defined class, reflection returns that as a "MethodInfo" with the name set to something like "op_Assign" or "op_Equality". I want to be able to capture these and list them properly, but I can't find anything in the MethodInfo object that is returned to accurately identify that I'm looking at an operator. I definitely don't want to just capture everything that starts with "op_", since that will most certainly (at some point) will pick up a method it's not supposed to. I know that other methods and properties that are "special cases" like this one have the "IsSpecialName" property set, but appearantly that's not the case with operators. I've been scouring the 'net and wracking my brain to two days trying to figure this one out, so any help will be greatly appreciated.

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  • Conversion between different template instantiation of the same template

    - by Naveen
    I am trying to write an operator which converts between the differnt types of the same implementation. This is the sample code: template <class T = int> class A { public: A() : m_a(0){} template <class U> operator A<U>() { A<U> u; u.m_a = m_a; return u; } private: int m_a; }; int main(void) { A<int> a; A<double> b = a; return 0; } However, it gives the following error for line u.m_a = m_a;. Error 2 error C2248: 'A::m_a' : cannot access private member declared in class 'A' d:\VC++\Vs8Console\Vs8Console\Vs8Console.cpp 30 Vs8Console I understand the error is because A<U> is a totally different type from A<T>. Is there any simple way of solving this (may be using a friend?) other than providing setter and getter methods? I am using Visual studio 2008 if it matters.

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