If I understand you correctly, then you declare the operator << for class Wrapper after the class declaration, and do not make it a friend to class Wrapper.
But what if Wrapper is a class that does not provide a getter for the data for the output? In other words what if I want to output data from my Wrapper object that is private and does not have a getter?
Is there a syntax for that as well?
NOTE: I forgot to...
Harinezumi
Joined: Feb 27 '08
Location: Budapest, Hungary
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Overloading operator << for template class
Hi,
I programmed a template class and I would like to overload the output operator for it.
...Code:#include <ostream> template <typename ContainedType> class Wrapper() { public: Wrapper() {/* ... */} /* ... */ template <typename U> friend std::ostream& operator<< (std::ostream out, const Wrapper<U>& -
You're right, I forgot about that kind of multiplication!
It is a programming exercise for me. I already have the class, it just occurred to me that coding the rank of the matrix as template parameter may be a good idea, but now I see it is obviously not.
Thanks for the posts!...Leave a comment:
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Matrix template class
Hello,
I created a template matrix class and some appropriate binary operators like:
The first line of each such binary operator is a check, like:Code:template <typename ContainedType> Matrix<ContainedType> operator+ (const Matrix<ContainedType>& lhs, const Matrix<ContainedType>& rhs) { ... }
...Code:assert(lhs.rows == rhs.rows &&
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OK, I understand what dominance does. What I don't get is why doesn't simple member function inheritance happen here, when it would be easier for the compiler than to guess what I wanted to do?
In this case the compiler guesses wrong, because I want to distinguish the member functions through their signatures (which I thought was default).Leave a comment:
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OK, I never heard of this rule before. Can it be turned off somehow? It's usually great that the compiler thinks for itself, but in this case, I'd rather it didn't. I would like to change the behavior of my setter in my derived class, but not the getter. And users of that class shouldn't need to be aware of how these methods are inherited.
Also, after looking up dominance, in all cases it said that it only applies to virtual inheritance....Leave a comment:
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Sorry, I posted the wrong compiler error.
It actually says this:
main.cpp: In function `int main()':
main.cpp:32: error: no matching function for call to `D2::Data()'
main.cpp:26: error: candidates are: virtual void D2::Data(const UserType&)Leave a comment:
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Virtual function signature problem
Hi,
while creating a hierarchy of classes I ran into a strange problem: it seems the compiler doesn't inherit virtual functions with the same name but different signature if only one of them is overridden in a derived class.
This is the smallest piece of code I could see the problem appear:
...Code:class UserType { public: UserType(float x) : x(x) {} float x; }; class -
Thanks arnaudk, that cleared my confusion....Leave a comment:
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By I/O operators I mean std::istream& operator >> (std::istream&, <class>&) and std::ostream& operator << (std::ostream&, <class>&), which are non-member friend functions.
How can a base implementation be provided for a pure virtual method?
Thanks weaknessforcats , the Visitor pattern really is what I wanted to achieve....Leave a comment:
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Serialization template base class
Hello,
I need help with the design of a serialization template base class.
The idea is that any class derived from this template base class would only need to implement the input and output operators and a named constructor, Create().
The code is something like this:
...Code:template <class SerializableClass> class Serializable { public: static SerializableClass* Unserialize(std::istream& -
Yes, I understand these.
My question is that is there a way to use the "public interface - private virtual hook method" pattern in a multi-level inheritance hierarchy?
(btw, is there a name for it?)...Leave a comment:
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The way of separating the public interface from the implementation in derived classes in the article above is great.
However, when I started using it, a question emerged: what about multiple levels of inheritance, where the most derived class wants to call function in a middle level class?
E.g.:
[CODE=cpp]class A
{
public:
A() {}
void AMethod() { AMethodHook(); }
private:...Leave a comment:
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Thanks, Savage, for the info! The missing piece of information was that when using virtual inheritance the most derived class needs to call the virtual base class.
In the given example I don't use multiple inheritance, because I reduced the code to the smallest chunk the problem appears in. However, the full code does use multiple inheritance....Leave a comment:
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But doesn't the specified constructor of VDer do that? It does call the constructor of Base. It definitely works that way, when virtual inheritance is not involved.Leave a comment:
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If I do that, the compiler will not complain. However, why should a derived class have to initialize its indirect base? It doesn't make sense in my opinion....Leave a comment:
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Problem with virtual inheritance
Hi,
I have a Base class, a class VDer that virtually inherits from it, and a Final class that inherits from VDer.
The Base class only has a constructor which has a parameter.
class Base {
public:
Base(const string& par) : par(par) {}
private:
string par;
};
class VDer : public virtual Base
{
public:
VDer1(const string& par)... -
Thanks, that's a great article! It's a shame that textbooks still use public virtual functions......Leave a comment:
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C++ class design - a class to inherit different functionality
Hello,
I have a base class Base with given member variables, getters and setters, but it doesn't do much on its own. Then there are functionalities (Func) which can use this base class's member functions to achieve some complex computation.
I would like to design this class structure in a way that a derived of Base, Derived can have added functionality with the use of Funcs, without further programming.
Here's... -
Thanks!
I looked it up, and it turns out that hash_map is now in __gnu_cxx namespace (for gcc)....Leave a comment:
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