What Is the Diamond Problem in C++? How to Spot It and How to Fix It

The Diamond Problem can arise in C++ when you use multiple inheritance. Here's what it is, how to spot it, and how to fix it.

Multiple inheritance in C++ is powerful, but a tricky tool, that often leads to problems if not used carefully—problems like the Diamond Problem.

In this article, we will discuss the Diamond Problem, how it arises from multiple inheritance, and what you can do to resolve the issue.

Multiple Inheritance in C++

Multiple Inheritance is a feature of Object-Oriented Programming (OOP) where a subclass can inherit from more than one superclass. In other words, a child class can have more than one parent.

The figure below shows a pictorial representation of multiple inheritances.

In the above diagram, class C has class A and class B as its parents.

If we consider a real-life scenario, a child inherits from its father and mother. So a Child can be represented as a derived class with “Father” and “Mother” as its parents. Similarly, we can have many such real-life examples of multiple inheritance.

In multiple inheritance, the constructors of an inherited class are executed in the order that they are inherited. On the other hand, destructors are executed in the reverse order of their inheritance.

Now let’s illustrate the multiple inheritance and verify the order of construction and destruction of objects.

Code Illustration of Multiple Inheritance

For the multiple inheritance illustration, we have exactly programmed the above representation in C++. The code for the program is given below.

The output we obtain from the above program is as follows:

Now if we check the output, we see that the constructors are called in order B, A, and C while the destructors are in the reverse order. Now that we know the basics of multiple inheritance, we move on to discuss the Diamond Problem.

The Diamond Problem, Explained

The Diamond Problem occurs when a child class inherits from two parent classes who both share a common grandparent class. This is illustrated in the diagram below:

Here, we have a class Child inheriting from classes Father and Mother . These two classes, in turn, inherit the class Person because both Father and Mother are Person.

As shown in the figure, class Child inherits the traits of class Person twice—once from Father and again from Mother. This gives rise to ambiguity since the compiler fails to understand which way to go.

This scenario gives rise to a diamond-shaped inheritance graph and is famously called “The Diamond Problem.”

Code Illustration of the Diamond Problem

Below we have represented the above example of diamond-shaped inheritance programmatically. The code is given below:

Following is the output of this program:

Now you can see the ambiguity here. The Person class constructor is called twice: once when the Father class object is created and next when the Mother class object is created. The properties of the Person class are inherited twice, giving rise to ambiguity.

Since the Person class constructor is called twice, the destructor will also be called twice when the Child class object is destructed.

Now if you have understood the problem correctly, let’s discuss the solution to the Diamond Problem.

How to Fix the Diamond Problem in C++

The solution to the diamond problem is to use the virtual keyword. We make the two parent classes (who inherit from the same grandparent class) into virtual classes in order to avoid two copies of the grandparent class in the child class.

Let’s change the above illustration and check the output:

Code Illustration to Fix the Diamond Problem

Here we have used the virtual keyword when classes Father and Mother inherit the Person class. This is usually called “virtual inheritance," which guarantees that only a single instance of the inherited class (in this case, the Person class) is passed on.

In other words, the Child class will have a single instance of the Person class, shared by both the Father and Mother classes. By having a single instance of the Person class, the ambiguity is resolved.

The output of the above code is given below:

Here you can see that the class Person constructor is called only once.

One thing to note about virtual inheritance is that even if the parameterized constructor of the Person class is explicitly called by Father and Mother class constructors through initialization lists, only the base constructor of the Person class will be called .

This is because there's only a single instance of a virtual base class that's shared by multiple classes that inherit from it.

To prevent the base constructor from running multiple times, the constructor for a virtual base class is not called by the class inheriting from it. Instead, the constructor is called by the constructor of the concrete class.

In the example above, the class Child directly calls the base constructor for the class Person.

Related: A Beginner's Guide to the Standard Template Library in C++

What if you need to execute the parameterized constructor of the base class? You can do so by explicitly calling it in the Child class rather than the Father or Mother classes.

The Diamond Problem in C++, Solved

The Diamond Problem is an ambiguity that arises in multiple inheritance when two parent classes inherit from the same grandparent class, and both parent classes are inherited by a single child class. Without using virtual inheritance, the child class would inherit the properties of the grandparent class twice, leading to ambiguity.

This can crop up frequently in real-world code, so it's important to address that ambiguity whenever it's spotted.

The Diamond Problem is fixed using virtual inheritance, in which the virtual keyword is used when parent classes inherit from a shared grandparent class. By doing so, only one copy of the grandparent class is made, and the object construction of the grandparent class is done by the child class.

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Diamond Problem in C++

The Diamond Inheritance Problem in C++ is something that can occur when performing multiple inheritance between Classes . Multiple Inheritance is the concept of inheriting multiple classes at once, instead of just one. If done incorrectly, it can result in the Diamond Problem.

What is the Diamond Inheritance Problem in C++?

The following image illustrates the situation under which the Diamond problem occurs.

Diamond Inheritance Problem in C++

The Class A, is inherited by both Class B and C. Then Class D performs multiple inheritance by inheriting both B and C. Now why does this cause a problem?

Well, let’s take a look at another diagram, that represents what actually ends up happening.

Diamond Problem C++

You may, or may not know, that when inheritance occurs between a parent and child class, an object of the parent is created and stored alongside the child object. That is how the functions and variables of the parent can be accessed.

Now if we apply this analogy to the above diagram, you will realize that the Object D, will end up having 4 more objects with it. Now the number of objects isn’t the problem, rather the problem is that we have two objects of Class A alongside Object D. This is a problem, because instead of one object, we have two objects of Class A. Other than performance reasons, what effect could this have? Let’s find out.

Problems caused by Diamond Inheritance

Let’s take a look at the actual code, and observe the problems being caused. As we mentioned earlier, due to Diamond Inheritance, the Object D will have two copies of Object A. Let’s run the below code to see proof of this fact.

As you can see, the Constructor for Class A was called twice, meaning two objects were created.

Digging Deeper in the Diamond Problem

Let’s take a look at a more detailed example, that shows a situation under which Diamond Inheritance can actually become a real problem, and throw an error.

Take a good look at this code. What we are doing here, is using the parameterized constructors to initialize the Objects for Class A. Class B and C are both passed two values, 5 and 8, which they both use to initialize to objects for Class A. One of the objects has the value 5, and one of them has the value 8.

The reason we did this, is so we can highlight the fact that there are two objects with two different values. Now the question is, when we try to use the getVar() function on object D, what happens? Normally, if there were just one object of Class A that was initialized to value “n”, the value “n” would be returned. But what happens in this case?

We can access each of the objects for Class A using the method above. Where we are performing the getVar() function on both the B and C Class object that are stored within Object D. As you can see, the value 5 and 8 are printed out.

But what happens when we use the getVar() function on D? Let’s find out.

See this error? It’s happening because it doesn’t know which object to use. It’s even showing in the error, that there are two objects which the getVar() function could be applied on.

How to solve the Diamond Problem in C++ using Virtual

The fix is very simple. All we need to do, is when inheriting when we make class B and class C inherit from Class A, we add the virtual keyword after the colon in the class name.

What this does, is shifts the responsibility of initializing Class A, to Class D. Previously Class B and C were responsible for initializing it, but since both were doing it, things became ambiguous. So if only Class D initializes Class A, there won’t be any problems as only one object is created.

Let’s modify our code now to include the Virtual keyword , and initialize Class A using Class D. (Although you can choose not to initialize it as well, and let the default constructor for Class A be used)

See our output now? There is no error, and only one object for Class A has been created. With this, our job is done and we can continue programming in peace.

This marks the end of the Diamond Problem in C++ Tutorial. Any suggestions or contributions for CodersLegacy are more than welcome. Questions regarding the tutorial content can be asked in the comments section below.

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Multiple Inheritance in C++ and the Diamond Problem

by Onur Tuna

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Unlike many other object-oriented programming languages, C++ allows multiple inheritance.

Multiple inheritance allows a child class to inherit from more than one parent class.

At the outset, it seems like a very useful feature. But a user needs to be mindful of a few gotchas while implementing this feature.

In the examples below, we will cover a few scenarios that one needs to be mindful about.

We’ll start with a simple example to explain this concept in C++.

The output of this code is as follows:

In the example above, we have a base class named as LivingThing . The Animal and Reptile classes inherit from it. Only the Animal class overrides the method breathe() . The Snake class inherits from the Animal and Reptile classes. It overrides their methods. In the example above, there is no problem. Our code works well.

Now, we’ll add a bit of complexity.

What if Reptile class overrides the breathe() method?

The Snake class would not know which breathe() method to call. This is the “Diamond Problem”.

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Diamond Problem

Look at the code below. It is like the code in the example above, except that we have overridden the breathe() method in the Reptile class.

If you try compiling the program, it won’t. You’ll be staring at an error message like the one below.

The error is due to the “Diamond Problem” of multiple inheritance. The Snake class does not know which breathe() method to call.

In the first example, only the Animal class had overridden the breathe() method. The Reptile class had not. Hence, it wasn’t very difficult for the Snake class to figure out which breathe() method to call. And the Snake class ended up calling the breathe() method of the Animal class.

In the second example, the Snake class inherits two breathe() methods. The breathe() method of the Animal and Reptile class. Since we haven’t overridden the breathe() method in the Snake class, there is ambiguity.

C++ has many powerful features such as multiple inheritance. But, it is not necessary that we use all the features it provides.

I don’t prefer using multiple inheritance and use virtual inheritance instead.

Virtual inheritance solves the classic “Diamond Problem”. It ensures that the child class gets only a single instance of the common base class.

In other words, the Snake class will have only one instance of the LivingThing class. The Animal and Reptile classes share this instance.

This solves the compile time error we receive earlier. Classes derived from abstract classes must override the pure virtual functions defined in the base class.

I hope you enjoyed this overview of multiple inheritance and the “Diamond Problem”.

If this article was helpful, tweet it .

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Multiple Inheritance is a feature of C++ where a class can inherit from more than one classes.  The constructors of inherited classes are called in the same order in which they are inherited. For example, in the following program, B’s constructor is called before A’s constructor.

A class can be derived from more than one base class.

(i) A CHILD class is derived from FATHER and MOTHER class (ii) A PETROL class is derived from LIQUID and FUEL class.

The destructors are called in reverse order of constructors.

In the above program, constructor of ‘Person’ is called two times. Destructor of ‘Person’ will also be called two times when object ‘ta1’ is destructed. So object ‘ta1’ has two copies of all members of ‘Person’, this causes ambiguities. The solution to this problem is ‘virtual’ keyword . We make the classes ‘Faculty’ and ‘Student’ as virtual base classes to avoid two copies of ‘Person’ in ‘TA’ class.

For example, consider the following program. 

In the above program, constructor of ‘Person’ is called once. One important thing to note in the above output is, the default constructor of ‘Person’ is called . When we use ‘virtual’ keyword, the default constructor of grandparent class is called by default even if the parent classes explicitly call parameterized constructor.

How to call the parameterized constructor of the ‘Person’ class?

The constructor has to be called in ‘TA’ class.

For example, see the following program. 

In general, it is not allowed to call the grandparent’s constructor directly, it has to be called through parent class. It is allowed only when ‘virtual’ keyword is used.

As an exercise, predict the output of following programs.

Question 1  

Question 2  

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

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C++: Diamond Problem and Virtual Inheritance

Summary: In this tutorial, we will learn what the diamond problem is, when it happens and how we can solve it using virtual inheritance in C++.

What is the Diamond Problem?

When we inherit more than one base class in the same derived class and all these base classes also inherit another but same single class (super parent), multiple references of the super parent class become available to the derived class.

So, it becomes unclear to the derived class, which version of the super parent class it should refer to.

Consider the following program for instance:

There is no syntactical error in the above program but still, if we try to compile then it returns the following compilation error:

line 24|error: request for member ‘name’ is ambiguous

This is because two instances of class A’s name() method is available for class D, one through class B, and the other through class C.

Diamond Problem in C++

In this case, the compiler gets confused and cannot decide which name() method it should refer to.

This ambiguity often occurs in the case of multiple inheritances and is popularly known as the diamond problem in C++.

To remove this ambiguity, we use virtual inheritance to inherit the super parent.

What is Virtual Inheritance?

Virtual inheritance in C++ is a type of inheritance that ensures that only one copy or instance of the base class’s members is inherited by the grandchild derived class.

It is implemented by prefixing the virtual keyword in the inheritance statement.

If we now apply virtual inheritance in our previous example, only one instance of class A would be inherited by class D (i.e. B::A and C::A will be treated as the same).

Virtual Inheritance in C++

Now because there is only one reference of class A’s instance is available to the child classes, we get the proper diamond-shaped inheritance.

Also, If we need to override any of the super parent class’s method (class A) in the child classes, we should override it till the very derived class, like the following. Otherwise, the compiler will throw no unique overrider error .

In this tutorial, we understood the concept of virtual inheritance and were able to solve the diamond problem using the same in C++.

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Multiple Inheritance in C++

C++ Course: Learn the Essentials

The capability of a class to derive properties and characteristics from another class is called Inheritance. This allows us to reuse and modify the attributes of the parent class using the object of the derived class.

The class whose member functions and data members are inherited is called the base class or parent class, and the class that inherits those members is called the derived class.

Introduction to Multiple Inheritance

Multiple Inheritance is the concept of inheritance in C++ by which we can inherit data members and member functions from multiple(more than one) base/parent class(es) so that the derived class can have properties from more than one parent class.

introduction to Multiple Inheritance in C++

In the image above, the derived class inherits data members and member functions from two different parent classes named Base Class 1 and Base Class 2 .

SHOWING AN EXAMPLE ANALOGY OF FLYING CAR AS MULTIPLE INHERITANCE

Diagram of Multiple Inheritance in C++

diagram of multiple inheritance

Syntax of Multiple Inheritance in C++

Here, there are two base classes: BaseClass1 and BaseClass2 . The DerivedClass inherits properties from both the base classes.

While we write the syntax for the multiple inheritance, we should first specify the derived class name and then the access specifier (public, private, or protected), and after that, the name of base classes.

We should also keep in mind the order of the base classes given while writing the multiple inheritance because the base class's constructor, which is written first, is called first.

As the order while writing the multiple inheritance was BaseClass2 and then BaseClass1 , the constructor will be called in that order only.

Now, changing the order.

Ambiguity Problem in Multiple Inheritance

In multiple inheritance, we derive a single class from two or more base or parent classes.

So, it can be possible that both the parent classes have the same-named member functions. While calling via the object of the derived class(if the object of the derived class invokes one of the same-named member functions of the base class), it shows ambiguity.

The online C++ compiler gets confused in selecting the member function of a class for the execution of a program and gives a compilation error.

Program to demonstrate the Ambiguity Problem in Multiple Inheritance in C++

Ambiguity Resolution in Multiple Inheritance

This problem can be solved using the scope resolution (::) operator. Using the scope resolution operator, we can specify the base class from which the function is called. We need to use the scope resolution (::) operator in the main() body of the code after we declare the object and while calling the member function by the object.

Ambiguity Resolved Code

How does multiple inheritance differ from multilevel inheritance.

DIAGRAM OF BOTH MULTIPLE AND MULTILEVEL INHERITANCE

Syntax of Multiple Inheritance:

The Diamond Problem

A diamond pattern is created when the child class inherits from the two base/parent class, and these parent classes have inherited from one common grandparent class(superclass).

DIAGRAM OF THE DIAMOND PROBLEM

Here, you can see that the superclass is called two times because of the diamond problem.

Solution of the Diamond Problem: The solution is to use the keyword virtual on the two parent classes, ClassA and ClassB . Two-parent classes with a common base class will now inherit the base class virtually and avoid the occurrence of copies of the base class in the child class ( ClassC here). This is called virtual inheritance. The virtual inheritance limits the passing of more than a single instance from the base class to the child class.

Fixed Code for the Diamond Problem

Output The result shows that ambiguity is removed using the virtual keyword:

Here in the output, we can see that the superclass's members are only inherited and have not formed copies.

TWO DIAGRAMS SHOWING HOW VIRTUAL INHERITANCE HELPS

How to Call the Parameterized Constructor of the Base Class?

To call the parameterized constructor of the base class, we need to explicitly specify the base class’s parameterized constructor in the derived class when the derived class’s parameterized constructor is called.

The parameterized constructor of the base/parent class should only be called in the parameterized constructor of the subclass. It cannot be called in the default constructor of the subclass.

Code Syntax:

Visibility Modes in Multiple Inheritance in C++

The visibility mode specifies the control/ accessibility over the inherited members of the base class within the derived classes. In C++, there are three visibility modes- public , protected , and private . The default visibility mode is private.

  • Private Visibility Mode: In Inheritance with private visibility mode, the public members(data members and member functions) and protected members of the parent/base classes become ‘private members' in the derived class.

Private Visibility Mode

  • Protected Visibility Mode: In inheritance with protected visibility mode, the public members(data members and member functions) and the protected members of the base/parent class become protected members of the derived class. As the private members are not inherited, they are not accessible directly by the object of the derived class. The difference between the private and the protected visibility mode is-

Protected Visibility Mode

  • Public Visibility Mode: In inheritance with public visibility mode, the public members(data members and member functions) of the base class(es) are inherited as the public members in the derived class, and the protected members(data members and member functions) of the base class are inherited as protected members in the derived class.

Public Visibility Mode

Advantages of Multiple Inheritance in C++

Multiple Inheritance is the inheritance process where a class can be derived from more than one parent class. The advantage of multiple inheritances is that they allow derived classes to inherit more properties and characteristics since they have multiple base/parent classes.

Example of Multiple Inheritance in C++

In the example of Multiple Inheritance, we will calculate the average of the two subjects.

The two subjects will have two different classes, and then we will make one class of Result which will be the derived class from the above two classes through multiple inheritance.

Now, we can access the member functions and data members directly when we inherit in public mode. We will use the data of both the parent classes, and then we will calculate the average marks.

  • The capability of a class to derive properties and characteristics from another class is called Inheritance.
  • Base Class - A class whose members are inherited.
  • Derived Class - A class that inherits the base class members.
  • In Multiple Inheritance in C++, we can inherit data members and member functions from multiple(more than one) base/parent class(es).
  • When the base classes have the same-named member functions and when we call them via derived class object. It shows ambiguity.
  • To solve the ambiguity problem, we should use the scope resolution operator (::) .
  • A diamond pattern is created when the child class inherits values and functions from the two base/parent classes, and these parent classes have inherited their values from one common grandparent class(superclass), which leads to duplication of functions.
  • To solve the diamond problem, we should use the virtual keyword, which restricts the duplicate inheritance of the same function.
  • There are three visibility modes in C++ for inheritance - public , protected , and private . The default visibility mode is private.
  • Polymorphism in C++ .

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How to calculate hp in dnd 5e

How to calculate hp 5e, how to calculate hp, how to calculate how tall i will be, how to calculate how pregnant you are, how to calculate how much you need to retire, how to calculate how much you make an hour, how to calculate how much you make a year, how to calculate how much you make a month, how to calculate how much water to drink, what is the diamond problem in c++ how to spot it and how to fix it.

solve diamond problem in c

C++ is a popular programming language used for a variety of applications. However, like any programming language, it has its quirks and challenges. One such challenge is known as the diamond problem, which occurs when multiple inheritance is used in a class hierarchy. This article will explore what the diamond problem is, how to spot it, and how to fix it.

What Is the Diamond Problem?

The diamond problem occurs in C++ when two classes inherit from a common base class, and a third class inherits from both of these classes. The resulting class hierarchy resembles a diamond shape, with the common base class at the top of the diamond and the two derived classes at the bottom corners. This makes it difficult for the third class, which inherits from both derived classes, to know which version of the inherited method to use. This can result in conflicts and ambiguity in the program.

How to Spot the Diamond Problem

To spot the diamond problem, look for a class hierarchy that resembles a diamond shape, as described above. If there are multiple derived classes that inherit from a common base class and a third class that inherits from both of these derived classes, the diamond problem is likely to occur.

Additionally, if there are conflicting methods or variables in the derived classes, this can also indicate the diamond problem. The third class that inherits from both derived classes may not know which version of the method to use, leading to conflicts and ambiguity in the program.

How to Fix the Diamond Problem

There are several ways to fix the diamond problem in C++. One solution is to use virtual inheritance, which ensures that only one instance of the base class is created in the derived class hierarchy. This eliminates the ambiguity and conflicts that arise in the diamond problem.

Virtual inheritance is implemented by using the keyword “virtual” when inheriting from the common base class. This tells the compiler to create a single instance of the base class in the derived class hierarchy. The syntax for virtual inheritance looks like this:

class Base {

class Derived1 : virtual public Base {

class Derived2 : virtual public Base {

class Third : public Derived1, public Derived2 {

In this example, both Derived1 and Derived2 inherit virtually from the Base class, and the Third class inherits from both Derived1 and Derived2.

Another solution is to use composition instead of inheritance. This involves creating an object of the base class inside the derived class, rather than inheriting from it. This reduces the complexity of the class hierarchy and eliminates the diamond problem.

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How to solve the Diamond Problem without using virtual function [closed]

i have this code as an example and we were given an openbook task to search for an answer on how to solve this code without using virtual keyword. i tired searching on google and tried myself but couldnt do it. so can anyone help?

  • diamond-problem

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  • 1 Assuming the dozen compile-time errors in this code will take care of themselves? –  WhozCraig Apr 12, 2022 at 5:10
  • A book will not be enough... he also needs a compiler. As we see the code, it was never tried to compile it. –  Klaus Apr 12, 2022 at 6:15
  • Solve what exactly? What is the problem? –  n. m. could be an AI Apr 12, 2022 at 6:16

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how can we solve diamond problem in c

What is the diamond problem in c++ how to spot it and how to fix it.

The Diamond Problem can arise in C++ when you use multiple inheritance. Here's what it is, how to spot it, and how to fix it.

Multiple inheritance in C++ is powerful, but a tricky tool, that often leads to problems if not used carefully—problems like the Diamond Problem.

In this article, we will discuss the Diamond Problem, how it arises from multiple inheritance, and what you can do to resolve the issue.

Multiple Inheritance in C++

Multiple Inheritance is a feature of Object-Oriented Programming (OOP) where a subclass can inherit from more than one superclass. In other words, a child class can have more than one parent.

The figure below shows a pictorial representation of multiple inheritances.

In the above diagram, class C has class A and class B as its parents.

If we consider a real-life scenario, a child inherits from its father and mother. So a Child can be represented as a derived class with “Father” and “Mother” as its parents. Similarly, we can have many such real-life examples of multiple inheritance.

In multiple inheritance, the constructors of an inherited class are executed in the order that they are inherited. On the other hand, destructors are executed in the reverse order of their inheritance.

Now let’s illustrate the multiple inheritance and verify the order of construction and destruction of objects.

Code Illustration of Multiple Inheritance

For the multiple inheritance illustration, we have exactly programmed the above representation in C++. The code for the program is given below.

The output we obtain from the above program is as follows:

Now if we check the output, we see that the constructors are called in order B, A, and C while the destructors are in the reverse order. Now that we know the basics of multiple inheritance, we move on to discuss the Diamond Problem.

The Diamond Problem, Explained

The Diamond Problem occurs when a child class inherits from two parent classes who both share a common grandparent class. This is illustrated in the diagram below:

Here, we have a class Child inheriting from classes Father and Mother . These two classes, in turn, inherit the class Person because both Father and Mother are Person.

As shown in the figure, class Child inherits the traits of class Person twice—once from Father and again from Mother. This gives rise to ambiguity since the compiler fails to understand which way to go.

This scenario gives rise to a diamond-shaped inheritance graph and is famously called “The Diamond Problem.”

Code Illustration of the Diamond Problem

Below we have represented the above example of diamond-shaped inheritance programmatically. The code is given below:

Following is the output of this program:

Now you can see the ambiguity here. The Person class constructor is called twice: once when the Father class object is created and next when the Mother class object is created. The properties of the Person class are inherited twice, giving rise to ambiguity.

Since the Person class constructor is called twice, the destructor will also be called twice when the Child class object is destructed.

Now if you have understood the problem correctly, let’s discuss the solution to the Diamond Problem.

How to Fix the Diamond Problem in C++

The solution to the diamond problem is to use the virtual keyword. We make the two parent classes (who inherit from the same grandparent class) into virtual classes in order to avoid two copies of the grandparent class in the child class.

Let’s change the above illustration and check the output:

Code Illustration to Fix the Diamond Problem

Here we have used the virtual keyword when classes Father and Mother inherit the Person class. This is usually called “virtual inheritance," which guarantees that only a single instance of the inherited class (in this case, the Person class) is passed on.

In other words, the Child class will have a single instance of the Person class, shared by both the Father and Mother classes. By having a single instance of the Person class, the ambiguity is resolved.

The output of the above code is given below:

Here you can see that the class Person constructor is called only once.

One thing to note about virtual inheritance is that even if the parameterized constructor of the Person class is explicitly called by Father and Mother class constructors through initialization lists, only the base constructor of the Person class will be called .

This is because there's only a single instance of a virtual base class that's shared by multiple classes that inherit from it.

To prevent the base constructor from running multiple times, the constructor for a virtual base class is not called by the class inheriting from it. Instead, the constructor is called by the constructor of the concrete class.

In the example above, the class Child directly calls the base constructor for the class Person.

Related: A Beginner's Guide to the Standard Template Library in C++

What if you need to execute the parameterized constructor of the base class? You can do so by explicitly calling it in the Child class rather than the Father or Mother classes.

The Diamond Problem in C++, Solved

The Diamond Problem is an ambiguity that arises in multiple inheritance when two parent classes inherit from the same grandparent class, and both parent classes are inherited by a single child class. Without using virtual inheritance, the child class would inherit the properties of the grandparent class twice, leading to ambiguity.

This can crop up frequently in real-world code, so it's important to address that ambiguity whenever it's spotted.

The Diamond Problem is fixed using virtual inheritance, in which the virtual keyword is used when parent classes inherit from a shared grandparent class. By doing so, only one copy of the grandparent class is made, and the object construction of the grandparent class is done by the child class.

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Diamond Problem in Inheritance

Diamond problem occurs when we use multiple inheritance in programming languages like C++ or Java.

Let’s understand this with one example.

Suppose there are four classes A, B, C and D. Class B and C inherit class A. Now class B and C contains one copy of all the functions and data members of class A.

Class D is derived from Class B and C. Now class D contains two copies of all the functions and data members of class A. One copy comes from class B and another copy comes from class C.

Let’s say class A have a function with name display(). So class D have two display() functions as I have explained above. If we call display() function using class D object then ambiguity occurs because compiler gets confused that whether it should call display() that came from class B or from class C. If you will compile above program then it will show error.

Diamond Problem in Inheritance

This kind of problem is called diamond problem as a diamond structure is formed (see the image).

How to Remove Diamond Problem in C++?

We can remove diamond problem by using virtual keyword. It can be done in following way.

You can see we have marked class B and C as virtual. Now compiler takes care that only one copy of data members and functions of class A comes to class D.

How to Remove Diamond Problem in Java?

To remove this problem java does not support multiple inheritance . Although we can achieve multiple inheritance using interfaces.

Comment below if you found anything missing or incorrect in above diamond problem tutorial.

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Introduction to object oriented programming concepts in java, classes and objects in java, this keyword in java, polymorphism in java, 1 thought on “diamond problem in inheritance”.

how can we solve diamond problem in c

In the above mentioned code, after virtually inheriting class A to both the classes B and C, it still doesn’t solves the problem.

Referring to your above code, if I call – int main() { D d1; d1.display(); /* It will still give compiler error, since display is overridden in both the classes B and C and it will still have 2 copies in class D (one from B and one from C) so here there will be ambiguity between class B::display() and C::display()*/ }

Please check and update accordingly, it seems quite misleading.

Thanks Amit

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CodersLegacy

CodersLegacy

Imparting knowledge to the Future

Diamond Problem in C++

The Diamond Inheritance Problem in C++ is something that can occur when performing multiple inheritance between Classes . Multiple Inheritance is the concept of inheriting multiple classes at once, instead of just one. If done incorrectly, it can result in the Diamond Problem.

What is the Diamond Inheritance Problem in C++?

The following image illustrates the situation under which the Diamond problem occurs.

Diamond Inheritance Problem in C++

The Class A, is inherited by both Class B and C. Then Class D performs multiple inheritance by inheriting both B and C. Now why does this cause a problem?

Well, let’s take a look at another diagram, that represents what actually ends up happening.

Diamond Problem C++

You may, or may not know, that when inheritance occurs between a parent and child class, an object of the parent is created and stored alongside the child object. That is how the functions and variables of the parent can be accessed.

Now if we apply this analogy to the above diagram, you will realize that the Object D, will end up having 4 more objects with it. Now the number of objects isn’t the problem, rather the problem is that we have two objects of Class A alongside Object D. This is a problem, because instead of one object, we have two objects of Class A. Other than performance reasons, what effect could this have? Let’s find out.

Problems caused by Diamond Inheritance

Let’s take a look at the actual code, and observe the problems being caused. As we mentioned earlier, due to Diamond Inheritance, the Object D will have two copies of Object A. Let’s run the below code to see proof of this fact.

As you can see, the Constructor for Class A was called twice, meaning two objects were created.

Digging Deeper in the Diamond Problem

Let’s take a look at a more detailed example, that shows a situation under which Diamond Inheritance can actually become a real problem, and throw an error.

Take a good look at this code. What we are doing here, is using the parameterized constructors to initialize the Objects for Class A. Class B and C are both passed two values, 5 and 8, which they both use to initialize to objects for Class A. One of the objects has the value 5, and one of them has the value 8.

The reason we did this, is so we can highlight the fact that there are two objects with two different values. Now the question is, when we try to use the getVar() function on object D, what happens? Normally, if there were just one object of Class A that was initialized to value “n”, the value “n” would be returned. But what happens in this case?

We can access each of the objects for Class A using the method above. Where we are performing the getVar() function on both the B and C Class object that are stored within Object D. As you can see, the value 5 and 8 are printed out.

But what happens when we use the getVar() function on D? Let’s find out.

See this error? It’s happening because it doesn’t know which object to use. It’s even showing in the error, that there are two objects which the getVar() function could be applied on.

How to solve the Diamond Problem in C++ using Virtual

The fix is very simple. All we need to do, is when inheriting when we make class B and class C inherit from Class A, we add the virtual keyword after the colon in the class name.

What this does, is shifts the responsibility of initializing Class A, to Class D. Previously Class B and C were responsible for initializing it, but since both were doing it, things became ambiguous. So if only Class D initializes Class A, there won’t be any problems as only one object is created.

Let’s modify our code now to include the Virtual keyword , and initialize Class A using Class D. (Although you can choose not to initialize it as well, and let the default constructor for Class A be used)

See our output now? There is no error, and only one object for Class A has been created. With this, our job is done and we can continue programming in peace.

This marks the end of the Diamond Problem in C++ Tutorial. Any suggestions or contributions for CodersLegacy are more than welcome. Questions regarding the tutorial content can be asked in the comments section below.

guest

Multiple Inheritance in C++ and the Diamond Problem

by Onur Tuna

1*QVZomxLNxnRYhm9gGIfYyw

Unlike many other object-oriented programming languages, C++ allows multiple inheritance.

Multiple inheritance allows a child class to inherit from more than one parent class.

At the outset, it seems like a very useful feature. But a user needs to be mindful of a few gotchas while implementing this feature.

In the examples below, we will cover a few scenarios that one needs to be mindful about.

We’ll start with a simple example to explain this concept in C++.

The output of this code is as follows:

In the example above, we have a base class named as LivingThing . The Animal and Reptile classes inherit from it. Only the Animal class overrides the method breathe() . The Snake class inherits from the Animal and Reptile classes. It overrides their methods. In the example above, there is no problem. Our code works well.

Now, we’ll add a bit of complexity.

What if Reptile class overrides the breathe() method?

The Snake class would not know which breathe() method to call. This is the “Diamond Problem”.

1*cI0TQYv7yOgSsHhfES1Kaw

Diamond Problem

Look at the code below. It is like the code in the example above, except that we have overridden the breathe() method in the Reptile class.

If you try compiling the program, it won’t. You’ll be staring at an error message like the one below.

The error is due to the “Diamond Problem” of multiple inheritance. The Snake class does not know which breathe() method to call.

In the first example, only the Animal class had overridden the breathe() method. The Reptile class had not. Hence, it wasn’t very difficult for the Snake class to figure out which breathe() method to call. And the Snake class ended up calling the breathe() method of the Animal class.

In the second example, the Snake class inherits two breathe() methods. The breathe() method of the Animal and Reptile class. Since we haven’t overridden the breathe() method in the Snake class, there is ambiguity.

C++ has many powerful features such as multiple inheritance. But, it is not necessary that we use all the features it provides.

I don’t prefer using multiple inheritance and use virtual inheritance instead.

Virtual inheritance solves the classic “Diamond Problem”. It ensures that the child class gets only a single instance of the common base class.

In other words, the Snake class will have only one instance of the LivingThing class. The Animal and Reptile classes share this instance.

This solves the compile time error we receive earlier. Classes derived from abstract classes must override the pure virtual functions defined in the base class.

I hope you enjoyed this overview of multiple inheritance and the “Diamond Problem”.

If this article was helpful, tweet it .

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how can we solve diamond problem in c

C++: Diamond Problem and Virtual Inheritance

Summary: In this tutorial, we will learn what the diamond problem is, when it happens and how we can solve it using virtual inheritance in C++.

What is the Diamond Problem?

When we inherit more than one base class in the same derived class and all these base classes also inherit another but same single class (super parent), multiple references of the super parent class become available to the derived class.

So, it becomes unclear to the derived class, which version of the super parent class it should refer to.

Consider the following program for instance:

There is no syntactical error in the above program but still, if we try to compile then it returns the following compilation error:

line 24|error: request for member ‘name’ is ambiguous

This is because two instances of class A’s name() method is available for class D, one through class B, and the other through class C.

Diamond Problem in C++

In this case, the compiler gets confused and cannot decide which name() method it should refer to.

This ambiguity often occurs in the case of multiple inheritances and is popularly known as the diamond problem in C++.

To remove this ambiguity, we use virtual inheritance to inherit the super parent.

What is Virtual Inheritance?

Virtual inheritance in C++ is a type of inheritance that ensures that only one copy or instance of the base class’s members is inherited by the grandchild derived class.

It is implemented by prefixing the virtual keyword in the inheritance statement.

If we now apply virtual inheritance in our previous example, only one instance of class A would be inherited by class D (i.e. B::A and C::A will be treated as the same).

Virtual Inheritance in C++

Now because there is only one reference of class A’s instance is available to the child classes, we get the proper diamond-shaped inheritance.

Also, If we need to override any of the super parent class’s method (class A) in the child classes, we should override it till the very derived class, like the following. Otherwise, the compiler will throw no unique overrider error .

In this tutorial, we understood the concept of virtual inheritance and were able to solve the diamond problem using the same in C++.

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how can we solve diamond problem in c

Wednesday, September 5, 2018

  • What is Diamond Problem in C#

Diamond Problem in C#

Basic knowledge of Inheritance in c#.

Why c# does not supports multiple inheritances, what is the diamond problem :.

diamond problem in c#

How can we resolve the diamond problem in c#?

Diamond Problem in C#

Real Time  Diamond Problem in C#  Example:  

diamond problem in c#

Real Time  Diamond Problem in C#  Solution:  

diamond problem in c#

To understand the concepts of Implicit and Explicit interface visit the following link.

  • Implicit Interface
  • Explicit Interface

2 comments:

Hi, The direction of the arrows in either "two classes B and C inherit from A" or "D inherits from both B and C" is switched they should in both cases either start from parent and go to the child or the opposite, depending on the pattern you choose for the pictures (as it does not seem like an UML diagram). Thanks Thanks

how can we solve diamond problem in c

Thanks Paulo, The given diagram is correct in that case because first i am trying to explain when the diamond problem is occurred. the "D inherits from both B and C" if we are trying to inherits both the same time then it does not allow and That is the diamond problem diagram...... Thanks for suggestion. Please let me know in case of any concerns.

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Diamond problem calculator.

What is a diamond problem diamond math problems, how to do diamond problems case 1: given two factors, case 2: given one factor, and the product or sum, case 3: given product and sum, while searching for factors, how to use diamond problem calculator.

Welcome to our diamond problem calculator, also known as a diamond problem solver . This intuitive tool allows you to enter any two numbers and the two others will appear. We've also prepared a compendium that answers all your burning questions about this topic.

Let's start by introducing what a diamond problem is and continue smoothly to some how to do diamond problems of various types tips. Are you ready?

Despite what you might think, the diamond problem doesn't have a lot in common with gemstones💎 or diamond rings💍 — though we can teach you how to calculate a diamond's weight . It is more closely related to what is often called a diamond in math ♦️ or cards🃏 - the rhombus, a quadrilateral shape. The diamond problem is a type of exercise that happens in a diamond shape 💠 - which we can also represent as a cross with 4 sections.

Diamond problems: common shapes of a task

So, what is the diamond problem in math ? It's where you fill in all four fields, related by some mathematical operation . The pattern of the numbers is constant:

  • On the left and right side of the diamond, you have two numbers, sometimes called factors;
  • In the top part you can find their product; and
  • In the bottom section - their sum.

Solving the diamond problem means that you know only two numbers out of four, and you need to find the missing ones . And that's all!

Cross with factors A on the left, B on the right, product in the top, and sum in the bottom

There are three main types of diamond problems, and the diamond problem calculator can deal with all of them. If you're wondering how to do diamond problems in each of these cases, scroll down to the next sections.

This is the easiest case: you have two numbers, A and B, and you need to find the sum and product of them. For example, let's say that we want to solve the diamond problem for factors 13 13 13 and 4 4 4 :

Setup of a problem with diamond

  • Calculate the product = 13 × 4 = 52 = 13 \times 4 = 52 = 13 × 4 = 52 , and write the number on top.
  • Find the sum = 13 + 4 = 17 = 13 + 4 = 17 = 13 + 4 = 17 , and input the value into the bottom part of the diamond.

Resolution of a probelm with diamond

You might meet this type of a diamond math problem in the first lesson about the diamonds - when your teacher first introduces the concept.

Let's have a look at a slightly more complicated case, where you have one of the basic numbers, and a product or a sum. The first thing to do is to calculate the factor missing from the diamond. Transform your equation is such a way to solve for the unknown value:

a) When you're given one factor and the sum , you can find a second factor by a simple subtraction:

Setup of a problem with diamond

With both factors in hand, simply multiply them to get the last number: product = 5 × 6 = 30 = 5 \times 6 = 30 = 5 × 6 = 30 .

Cross with factors 5 on the left, 6 on the right, product 30 in the top, and sum 11 in the bottom

b) If you know one factor and the product , divide the product by the factor to find the second product:

Cross with factors 9 on the left, and product 63 in the top

Then calculate the sum , use the following expression: sum = factor  A + factor  B = 9 + 7 = 16 = \text{factor}\ A + \text{factor}\ B = 9 + 7 = 16 = factor   A + factor   B = 9 + 7 = 16 .

Cross with factors 9 on the left, 7 on the right, product 63 in the top, and sum 16 in the bottom

Remember, you can always quickly solve these diamonds or verify your answers with our diamond problem calculator.

Now we're coming to the last issue and the most common diamond problem: the case where you know the sum and the product of the two numbers, but you don't actually know the numbers themselves.

This type of diamond math problem is helpful when you're learning about factoring a quadratic equation. Why?

Let's say that we have a quadratic equation:

We would like to factor this equation, meaning that we'd like to present it in a form:

How to find these numbers - the roots of the quadratic equation ? You know that their product must be equal to 12 12 12 , and that their sum is equal to 7 7 7 . And that's exactly what you're trying to find out in the diamond problem! 🙂 You can rewrite this question in the form of a diamond:

Cross with question marks on the left and right,product 12 in the top, and sum 7 in the bottom

How to solve such a problem?

  • Start with the top number - the product of two numbers. Write down all possible pairs of numbers that give this as their product. You can, for example, calculate the prime factorization if it's a more complicated case. In our example, the product is equal to 12 - which two integer numbers could be multiplied together? The order of the factors doesn't matter, as multiplication (and addition) are commutative:

Don't forget the negative numbers:

  • Sum these two numbers , and check which combination gives the desired sum of 7:

And here it is! We can stop here, as we've found the two numbers which meet the condition 🎉

🙋 Eager to know more about quadratic formulas? Visit our quadratic formula calculator !

Sometimes it's very easy to guess the solution, as there are not many options. We're sure that you'll solve this a diamond problem in no time!

Cross with question marks on the left and right,product 7 in the top, and sum 8 in the bottom

If not, enter the numbers into our diamond problem solver. That wasn't so difficult, was it? 🤦

It's really easy, believe us!

All you need to do is to input any two numbers and the diamond problem solver will find out the other two . What's more, the tool displays the solution in a diamond form. What more could you wish for? 😎

Please notice that in some specific cases you'll need to hit the refresh button ⟳ to use the calculator again 👍

What are the other numbers in the diamond if the left and right are -4 and 8?

The top number is -32, and the bottom is 4. To find the top, we multiply the side numbers. We add them together to find the bottom.

What is the diamond problem used for in mathematics?

We use the diamond problem in addition, subtraction, multiplication, and division in maths. It is used to calculate integers, decimals, and fractions and for factoring trinomials.

How do I solve the diamond for fractions?

Assuming that you are given two fractions on the left and right sides, say 1 / 2 and 5 / 6 , follow these steps to solve the problem:

Find the product of the fractions: 1 / 2 × 5 / 6 = 5 / 12

Place this answer ( 5 / 12 ) at the top:

Find the sum of the fractions: 1 / 2 + 5 / 6 = 6 / 12 + 10 / 12 = 16 / 12

Place this answer ( 16 / 12 ) at the bottom.

Voila! You solved the diamond problem.

How do I find the right and left numbers in the diamond?

Assuming the top number is 35 , and the bottom is 12 . Follow these steps to find the numbers to the right and left:

  • Find the factors of the top number: 35, 1 7, 5
  • Identify the factors which, when added together, equal to the bottom number: 7, 5
  • Place these numbers on either side.

That's it. You have solved the diamond problem for the right and left numbers.

Dividing radicals

Surface area to volume ratio.

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You are here, c program to print diamond pattern.

The diamond pattern in C language: This code prints a diamond pattern of stars. The diamond shape is as follows:

Diamond pattern program in C

int main ( ) {   int n , c , k ;

  printf ( "Enter number of rows \n " ) ;   scanf ( "%d" , & n ) ;

  for ( k = 1 ; k <= n ; k ++ )   {     for ( c = 1 ; c <= n - k ; c ++ )       printf ( " " ) ;

    for ( c = 1 ; c <= 2 * k - 1 ; c ++ )       printf ( "*" ) ;

    printf ( " \n " ) ;   }

  for ( k = 1 ; k <= n - 1 ; k ++ )   {     for ( c = 1 ; c <= k ; c ++ )       printf ( " " ) ;

    for ( c = 1 ; c <= 2 * ( n - k ) - 1 ; c ++ )       printf ( "*" ) ;

Diamond pattern C program output

Download Diamond program.

C program to print diamond using recursion

void print ( int ) ;

int main ( ) {     int rows ;

    scanf ( "%d" , & rows ) ;

   print ( rows ) ;

    return 0 ; }

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C++ Course: Learn the Essentials

The capability of a class to derive properties and characteristics from another class is called Inheritance. This allows us to reuse and modify the attributes of the parent class using the object of the derived class.

The class whose member functions and data members are inherited is called the base class or parent class, and the class that inherits those members is called the derived class.

Introduction to Multiple Inheritance

Multiple Inheritance is the concept of inheritance in C++ by which we can inherit data members and member functions from multiple(more than one) base/parent class(es) so that the derived class can have properties from more than one parent class.

introduction to Multiple Inheritance in C++

In the image above, the derived class inherits data members and member functions from two different parent classes named Base Class 1 and Base Class 2.

SHOWING AN EXAMPLE ANALOGY OF FLYING CAR AS MULTIPLE INHERITANCE

Diagram of Multiple Inheritance in C++

diagram of multiple inheritance

Syntax of Multiple Inheritance in C++

Here, there are two base classes: BaseClass1 and BaseClass2. The DerivedClass inherits properties from both the base classes.

While we write the syntax for the multiple inheritance, we should first specify the derived class name and then the access specifier (public, private, or protected), and after that, the name of base classes.

We should also keep in mind the order of the base classes given while writing the multiple inheritance because the base class's constructor, which is written first, is called first.

As the order while writing the multiple inheritance was BaseClass2 and then BaseClass1 , the constructor will be called in that order only.

Now, changing the order.

Ambiguity Problem in Multiple Inheritance

In multiple inheritance, we derive a single class from two or more base or parent classes.

So, it can be possible that both the parent classes have the same-named member functions. While calling via the object of the derived class(if the object of the derived class invokes one of the same-named member functions of the base class), it shows ambiguity.

The online C++ compiler gets confused in selecting the member function of a class for the execution of a program and gives a compilation error.

Program to demonstrate the Ambiguity Problem in Multiple Inheritance in C++

Ambiguity Resolution in Multiple Inheritance

This problem can be solved using the scope resolution (::) operator. Using the scope resolution operator, we can specify the base class from which the function is called. We need to use the scope resolution (::) operator in the main() body of the code after we declare the object and while calling the member function by the object. Syntax:

Ambiguity Resolved Code

How does multiple inheritance differ from multilevel inheritance.

DIAGRAM OF BOTH MULTIPLE AND MULTILEVEL INHERITANCE

Syntax of Multiple Inheritance:

The Diamond Problem

A diamond pattern is created when the child class inherits from the two base/parent class, and these parent classes have inherited from one common grandparent class(superclass).

DIAGRAM OF THE DIAMOND PROBLEM

Here, you can see that the superclass is called two times because of the diamond problem.

Solution of the Diamond Problem: The solution is to use the keyword virtual on the two parent classes, ClassA and ClassB . Two-parent classes with a common base class will now inherit the base class virtually and avoid the occurrence of copies of the base class in the child class ( ClassC here). This is called virtual inheritance. The virtual inheritance limits the passing of more than a single instance from the base class to the child class.

Fixed Code for the Diamond Problem

Output The result shows that ambiguity is removed using the virtual keyword:

Here in the output, we can see that the superclass's members are only inherited and have not formed copies.

TWO DIAGRAMS SHOWING HOW VIRTUAL INHERITANCE HELPS

How to Call the Parameterized Constructor of the Base Class?

To call the parameterized constructor of the base class, we need to explicitly specify the base class’s parameterized constructor in the derived class when the derived class’s parameterized constructor is called.

The parameterized constructor of the base/parent class should only be called in the parameterized constructor of the subclass. It cannot be called in the default constructor of the subclass.

Code Syntax:

Visibility Modes in Multiple Inheritance in C++

The visibility mode specifies the control/ accessibility over the inherited members of the base class within the derived classes. In C++, there are three visibility modes- public , protected , and private . The default visibility mode is private.

  • Private Visibility Mode: In Inheritance with private visibility mode, the public members(data members and member functions) and protected members of the parent/base classes become ‘private members' in the derived class.

Private Visibility Mode

  • Protected Visibility Mode: In inheritance with protected visibility mode, the public members(data members and member functions) and the protected members of the base/parent class become protected members of the derived class. As the private members are not inherited, they are not accessible directly by the object of the derived class. The difference between the private and the protected visibility mode is-

Protected Visibility Mode

  • Public Visibility Mode: In inheritance with public visibility mode, the public members(data members and member functions) of the base class(es) are inherited as the public members in the derived class, and the protected members(data members and member functions) of the base class are inherited as protected members in the derived class.

Public Visibility Mode

Advantages of Multiple Inheritance in C++

Multiple Inheritance is the inheritance process where a class can be derived from more than one parent class. The advantage of multiple inheritances is that they allow derived classes to inherit more properties and characteristics since they have multiple base/parent classes.

Example of Multiple Inheritance in C++

In the example of Multiple Inheritance, we will calculate the average of the two subjects.

The two subjects will have two different classes, and then we will make one class of Result which will be the derived class from the above two classes through multiple inheritance.

Now, we can access the member functions and data members directly when we inherit in public mode. We will use the data of both the parent classes, and then we will calculate the average marks.

  • The capability of a class to derive properties and characteristics from another class is called Inheritance.
  • Base Class - A class whose members are inherited.
  • Derived Class - A class that inherits the base class members.
  • In Multiple Inheritance in C++, we can inherit data members and member functions from multiple(more than one) base/parent class(es).
  • When the base classes have the same-named member functions and when we call them via derived class object. It shows ambiguity.
  • To solve the ambiguity problem, we should use the scope resolution operator (::) .
  • A diamond pattern is created when the child class inherits values and functions from the two base/parent class, and these parent classes have inherited their values from one common grandparent class(superclass), which leads to duplication of functions.
  • To solve the diamond problem, we should use the virtual keyword, which restricts the duplicate inheritance of the same function.
  • There are three visibility modes in C++ for inheritance - public , protected , and private . The default visibility mode is private.
  • Polymorphism in C++ .

What is a diamond problem in Object-Oriented Programming?

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Inheritance is a key feature of object-oriented programming that involves acquiring or inheriting all of the attributes and behaviors of one class and then extending or specializing them.

Inheritance can be seen everywhere in the world. For example, a newborn child inherits attributes (hair, color, etc.) from their father and mother. But after acquiring attributes from their parents, they also develop their own personalities on top of those attributes.

Consider the example of a car.

widget

Both electric and gasoline cars inherit the properties of a car.

Now, there is a special case if there is another class – a Hybrid class, for example – that inherits both the Electric and Gasoline class. We can see in the diagram that it will form a diamond.

widget

The hybrid car is both an electric car and a gasoline car. These kinds of special cases will result in a diamond problem .

This diamond creates a problem, because now the Hybrid class has two copies of the Car class for each path.

Let’s look at the following code snippet.

If you make a Hybrid class object in the main, you see that the Car Constructor is called two times. This is because of the diamond problem. The Hybrid class object has two copies of the Car class for each of its parents, respectively.

This might not appear to be a big issue. For larger programs, however, in which the grandparent also contains tens of classes above it, the overhead of this duplication is tremendous.

So, how can this problem be solved?

The above problem can be solved by writing the keyword virtual . When we use virtual keyword, it is called virtual inheritance. When we use virtual inheritance, we are guaranteed to get only a single instance of the common base class. In other words, the hybrid class will have only a single instance of the car class, shared by both the Electric and Gasoline classes. By having a single instance of car, we’ve resolved the problem. We will make both the Electric and Gasoline classes into virtual base classes.

After updating the code, we can see that the hybrid object only contains one Car class copy.

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How can I avoid the Diamond of Death when using multiple inheritance?

http://en.wikipedia.org/wiki/Diamond_problem

I know what it means, but what steps can I take to avoid it?

  • multiple-inheritance

Mateen Ulhaq's user avatar

  • 1 I want to say "don't use multiple inheritance," but that's just being a cad. I'd love to see a good answer to this, too. –  Chris Charabaruk Sep 26, 2008 at 1:43
  • 2 "Diamond of Death" is a bit dramatic. What exactly do you want to know. –  Martin York Sep 26, 2008 at 3:57
  • 6 It's widely known as the Deadly Diamond of Death. Google it. –  ilitirit Sep 26, 2008 at 10:56
  • 13 Google tells me it'susually known as the "Diamond Problem", except in the Java community, where the more drastic term is used to justify why Java "solves" the problem by disallowing it. –  wolfgang Dec 15, 2011 at 9:55
  • 1 There is no "death" here. Both virtual and "standard" inheritance have their use (very rarely, though). –  Alexandre C. Mar 8, 2012 at 20:24

9 Answers 9

A practical example:

Notice how class D inherits from both B & C. But both B & C inherit from A. That will result in 2 copies of the class A being included in the vtable.

To solve this, we need virtual inheritance. It's class A that needs to be virtually inherited. So, this will fix the issue:

Mark Ingram's user avatar

  • 7 That's only avoiding A being twice in memory, it does not avoid any problems caused by the Diamond. See tinyurl.com/abtjcb ; how do you implement getDepartment, that it always returns the right thing? You can't! Your design is flawed. See tinyurl.com/ccjnk6 –  Mecki Feb 25, 2009 at 16:31
  • 6 That's what scope is for. Alternatively you can use the "using" statement in class D. –  Mark Ingram Feb 26, 2009 at 9:12
  • 3 Isn't this answer only valid for classes you have control over? If B and C are in a library provided by someone else, or they're part of a code base you cannot change this 'solution' doesn't work at all. It also goes against the whole principle of OOP that a base class shouldn't be concerned with the derived classes, but here B and C suddenly have to change because of some class D that was added later in the day. –  jbx Oct 18, 2015 at 20:12
  • Doesn't work for me. Got linker "vtable" error. See my "answer" post below. –  Balazs Kelemen Feb 4, 2021 at 21:27

I'd stick to using multiple inheritance of interfaces only. While multiple inheritance of classes is attractive sometimes, it can also be confusing and painful if you rely on it regularly.

Bob Somers's user avatar

  • 11 @Arafangion C++ does have interfaces, although it is not a language construct as for example found in Java. Instead, they are just pure virtual base classes. –  jlh Jun 11, 2012 at 12:01
  • @jlh: I'll conceed that point, although I'd contend that while C++ itself doesn't have interfaces, the language does allow you to implement them. –  Arafangion Jun 11, 2012 at 23:58
  • 4 I never met somebody who did not understand that it would mean inheriting pure abstract classes in this context –  BlueTrin Nov 8, 2014 at 9:00

virtual inheritance. That's what it's there for.

eduffy's user avatar

  • 2 Where in the inheritance hierarchy? –  ilitirit Sep 26, 2008 at 1:47
  • If you have B and C derived from A, and D derived from B and C, then B and C must both declare A as a virtual base. Specifically, each instance of virtual inheritance of the same class is collapsed into one class. Any non-virtual ones will not be collapsed, causing the diamond to recur. –  coppro Sep 26, 2008 at 2:03
  • 1 While virtual inheritence is the feature for getting around the Diamond of Death problem, I think that there are better ways to work around the problem. Namely, inheriting from abstract base classes (interface classes) instead of inheriting from multiple concrete classes. –  Nick Haddad Sep 26, 2008 at 13:03

Inheritance is a strong, strong weapon. Use it only when you really need it. In the past, diamond inheritance was a sign that I was going to far with classification, saying that a user is an "employee" but they are also a "widget listener", but also a ...

In these cases, it's easy to hit multiple inheritance issues.

I solved them by using composition and pointers back to the owner:

Yes, access rights are different, but if you can get away with such an approach, without duplicating code, it's better because it's less powerful. (You can save the power for when you have no alternative.)

  • 1 And what you did is that you multiplied your memory usage by a lot. No thanks. –  luke1985 Nov 3, 2015 at 19:49
  • 1 Composition vs Inheritance. Fight! –  Alexander Shishenko Feb 3, 2016 at 10:45

In this the attributes of Class A repeated twice in Class D which makes more memory usage... So to save memory we make a virtual attribute for all inherited attributes of class A which are stored in a Vtable.

Tisho's user avatar

Well, the great thing about the Dreaded Diamond is that it's an error when it occurs. The best way to avoid is to figure out your inheritance structure beforehand. For instance, one project I work on has Viewers and Editors. Editors are logical subclasses of Viewers, but since all Viewers are subclasses - TextViewer, ImageViewer, etc., Editor does not derive from Viewer, thus allowing the final TextEditor, ImageEditor classes to avoid the diamond.

In cases where the diamond is not avoidable, using virtual inheritance. The biggest caveat, however, with virtual bases, is that the constructor for the virtual base must be called by the most derived class, meaning that a class that derives virtually has no control over the constructor parameters. Also, the presence of a virtual base tends to incur a performance/space penalty on casting through the chain, though I don't believe there is much of a penalty for more beyond the first.

Plus, you can always use the diamond if you are explicit about which base you want to use. Sometimes it's the only way.

coppro's user avatar

I would suggest a better class design. I'm sure there are some problems that are solved best through multiple inheritance, but check to see if there is another way first.

If not, use virtual functions/interfaces.

user17720's user avatar

  • 1 " check to see if there is another way first " Why? –  curiousguy Nov 1, 2011 at 3:17

Use inheritance by delegation. Then both classes will point to a base A, but have to implement methods that redirect to A. It has the side effect of turning protected members of A into "private" members in B,C, and D, but now you don't need virtual, and you don't have a diamond.

Lee Louviere's user avatar

This is all I have in my notes about this topic. I think this would help you.

The diamond problem is an ambiguity that arises when two classes B and C inherit from A, and class D inherits from both B and C. If there is a member in A that B and C, and D does not override it, then which member does D inherit: that of B, or that of C?

In the above example, both B & C inherit A, and they both have a single copy of A. However D inherits both B & C, therefore D has two copies of A, one from B and another from C. If we need to access the data member an of A through the object of D, we must specify the path from which the member will be accessed: whether it is from B or C because most compilers can’t differentiate between two copies of A in D.

There are 4 ways to avoid this ambiguity:

1- Using the scope resolution operator we can manually specify the path from which a data member will be accessed, but note that, still there are two copies (two separate subjects) of A in D, so there is still a problem.

2- Using static_cast we can specify which path the compiler can take to reach to data member, but note that, still there are two copies (two separate suobjects) of A in D, so there is still a problem.

3- Using overridden, the ambiguous class can overriden the member, but note that, still there are two copies (two separate suobjects) of A in D, so there is still a problem.

3- Using virtual inheritance, the problem is completely solved: If the inheritance from A to B and the inheritance from A to C are both marked "virtual", C++ takes special care to create only one A subobject,

Note that " both " B and C have to be virtual, otherwise if one of them is non-virtual, D would have a virtual A subobject and another non-virtual A subobject, and ambiguity will be still taken place even if class D itself is virtual. For example, class D is ambiguous in all of the following:

mada's user avatar

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5 things to know about Japan's Fukushima water release in the Pacific

Geoff Brumfiel, photographed for NPR, 17 January 2019, in Washington DC.

Geoff Brumfiel

Kat Lonsdorf

how can we solve diamond problem in c

Storage tanks for contaminated water at the Fukushima Daiichi nuclear power plant are near capacity. Philip Fong/AFP via Getty Images hide caption

Storage tanks for contaminated water at the Fukushima Daiichi nuclear power plant are near capacity.

Workers in Japan have started releasing treated radioactive water from the Fukushima Daiichi nuclear power plant into the Pacific Ocean. The plant was destroyed in a 2011 earthquake and massive tsunami, and water has been accumulating ever since.

On Thursday, the Chinese government announced it was immediately suspending aquatic imports, such as seafood, from Japan.

A review by the U.N.'s nuclear watchdog says the discharge will have a negligible radiological impact to people and the environment, but some nations remain concerned. Here's what the Japanese government is doing, and why.

Why is there water at the Fukushima plant?

After the 2011 Tohoku earthquake and tsunami, several reactors melted down at the Fukushima Daiichi nuclear power plant. To avert further disaster, workers flooded the reactors with water, and that water quickly became highly contaminated. The plant is now offline and the reactors are defunct, but they still need to be cooled, which is why wastewater continues to accumulate. In the years since the accident, groundwater has also filtered into the site, and some of it has become contaminated as well.

Dealing with all this radioactive water has been a huge technical challenge for the Japanese government. Currently, some 350 million gallons are being stored in more than 1,000 tanks on-site, according to Japanese authorities. The tanks are nearing capacity and the site can't fit any more, so some of the water needs to be released, according to the government.

how can we solve diamond problem in c

Japan has built an elaborate system to filter out radioactive contamination from the water. But some forms of radiation cannot be filtered. Philip Fong /AFP via Getty Images hide caption

Japan has built an elaborate system to filter out radioactive contamination from the water. But some forms of radiation cannot be filtered.

Can't they just filter the radioactive particles out of the water?

The government has been working on a complex filtration system that removes most of the radioactive isotopes from the water. Known as the Advanced Liquid Processing System (or ALPS, for short), it can remove several different radioactive contaminants from the water.

The authorities have used ALPS and other systems to remove some of the most hazardous isotopes, like cesium-137 and strontium-90.

But there's a radioactive isotope that they cannot filter out: tritium. Tritium is an isotope of hydrogen, and hydrogen is part of the water itself (H 2 0). So it is impossible to create a filter that could remove the tritium.

Recovering Fukushima

Recovering Fukushima

In Rural Fukushima, 'The Border Between Monkeys And Humans Has Blurred'

In Rural Fukushima, 'The Border Between Monkeys And Humans Has Blurred'

So how does the japanese government plan to release this water safely.

There are a couple of parts to the plan. First, they are going to dilute the water with seawater, so that there's a lot less tritium in every drop. The government says they will bring tritium levels well below all safety limits, and below the level released by some operating nuclear plants. Second, they're taking that diluted water and passing it through a tunnel under the seafloor to a point off the coast of Fukushima in the Pacific Ocean. That will dilute it further.

Finally, they are going to do this slowly. It will take decades to empty all these tanks.

how can we solve diamond problem in c

South Korea's main opposition Democratic Party members hold electric candles and a sign reading "No Fukushima nuclear contaminated water!" during a rally against Japan's plan on Wednesday. Other Pacific nations are also worried by the release. Jung Yeon-Je /AFP via Getty Images hide caption

South Korea's main opposition Democratic Party members hold electric candles and a sign reading "No Fukushima nuclear contaminated water!" during a rally against Japan's plan on Wednesday. Other Pacific nations are also worried by the release.

Do others think this process is safe?

The Japanese government maintains that, especially when compared to some of the other radioactive material at the site, tritium isn't all that bad. Its radioactive decay is relatively weak, and because it's part of water, it actually moves through biological organisms rather quickly. And its half-life is 12 years, so unlike elements such as uranium-235, which has a half-life of 700 million years, it won't be in the environment all that long.

Given all that, the government believes that this is the safest option available.

Worries over seafood safety mount as Japan releases Fukushima water into the Pacific

Worries over seafood safety mount as Japan releases Fukushima water into the Pacific

The International Atomic Energy Agency has peer-reviewed this plan and believes it is consistent with international safety standards. The IAEA also plans to conduct independent monitoring to make sure the discharge is done safely.

"The risk is really, really, really low. And I would call it not a risk at all," says Jim Smith, a professor of environmental science at the University of Portsmouth. He's spent the past few decades studying radioactivity in waterways after nuclear accidents, including at Chernobyl.

"We've got to put radiation in perspective, and the plant release — if it's done properly — then the doses that people get and the doses that the ecosystem get just won't be significant, in my opinion," Smith says.

Fukushima Has Turned These Grandparents Into Avid Radiation Testers

Fukushima Has Turned These Grandparents Into Avid Radiation Testers

After 2011 Disaster, Fukushima Embraced Solar Power. The Rest Of Japan Has Not

After 2011 Disaster, Fukushima Embraced Solar Power. The Rest Of Japan Has Not

Edwin Lyman is the director of nuclear power safety at the Union of Concerned Scientists in Washington, D.C. He says that out of the limited options Japan has for this wastewater, none of them are good, but: "In my view, I think that their current plan, unfortunately is probably the least bad of a bunch of bad options," he says.

"The idea of deliberately discharging hazardous substances into the environment, into the ocean is repugnant," Lyman says. "But unfortunately, if you do look at it from the technical perspective, it's hard to argue that the impacts of this discharge would be worse than those that are occurring at nuclear power plants that are operating worldwide."

But not everyone agrees that discharging the water is the best option. Ken Buesseler, a senior scientist at the Woods Hole Oceanographic Institution, thinks it would have been better to keep the contaminated water on land, "where it's much easier to monitor." Options could have included mixing it into concrete to immobilize it.

Buesseler doesn't think the water will pose a risk across the Pacific. "We don't expect to see widespread direct health effects, either on humans or on marine life," he says. But he does think that non-tritium contaminates missed by the ALPS system could build up over time near the shore.

"Nearshore in Japan could be affected in the long term because of accumulation of non-tritium forms of radioactivity," he says. That could ultimately hurt fisheries in the area.

And Buesseler worries about the message sent to other nations that may be eager to dispose of nuclear waste at sea.

How are other nations responding to Japan's decision?

Other nations have expressed concern over Japan's plan. South Korea has seen mounting public protests over the decision.

Buesseler consults for the Pacific Islands Forum , a coalition of nations including the Marshall Islands and Tahiti that are also apprehensive about Japan's decision. He notes that many of these countries were subjected to high levels of radioactive fallout as a result of atmospheric nuclear tests during the Cold War. "There are islands they can't return to...because of legacy contamination," Buesseler says.

Moreover, "they're suffering in many ways from climate change and sea level rise more than the rest of the world," he says. From their perspective, Japan's release into the Pacific "is just one insult, environmentally, among others."

  • fukushima daiichi
  • nuclear waste
  • Pacific Ocean
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how can we solve diamond problem in c

The Diamond Problem can arise in C++ when you use multiple inheritance. Here's what it is, how to spot it, and how to fix it. Readers like you help support MUO. When you make a purchase using links on our site, we may earn an affiliate commission. Read More.

diamond-problem-solution. Published June 12, 2019 at 3000 × 1948 in diamond-problem-solution. ← Previous Next →.

To solve the famous diamond problem, we have interfaces. Like (I am using C#) public interface IAInterface { void aMethod (); } public interface IBInterface { void aMethod (); } Now public class aClass : IAInterface, IBInterface { public void aMethod () { } }

Diamond problem occurs when we use multiple inheritance in programming languages like C++ or Java. Let's understand this with one example. Diamond Problem in Inheritance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 class A { void display() { } } class B : public A{ void display() { } }

What is the Diamond Inheritance Problem in C++? The following image illustrates the situation under which the Diamond problem occurs. The Class A, is inherited by both Class B and C. Then Class D performs multiple inheritance by inheriting both B and C. Now why does this cause a problem?

by Onur Tuna Multiple Inheritance in C++ and the Diamond Problem Unlike many other object-oriented programming languages, C++ allows multiple inheritance. Multiple inheritance allows a child class to inherit from more than one parent class. At the outset, it seems like a very useful feature. But a user needs to

Solving the Diamond Problem with Virtual Inheritance By Andrei Milea Multiple inheritance in C++ is a powerful, but tricky tool, that often leads to problems if not used carefully. This article will teach you how to use virtual inheritance to solve some of these common problems programmers run into.

Summary: In this tutorial, we will learn what the diamond problem is, when it happens and how we can solve it using virtual inheritance in C++. What is the Diamond Problem?

Any solution to this? c++ inheritance name-collision Share Improve this question Follow edited Jul 26, 2017 at 7:38 Jarod42 202k 14 178 299 asked Jul 26, 2017 at 6:25 BSalunke 11.5k 8 34 68 11 There's no diamond here. You just have a name clash from two unrelated base classes, and virtual inheritance cannot do anything about that.

Yeah, that is one of the most popular and efficient solutions to the diamond problem. class base { -- }; class der1:public base { -- }; class der2:public base { -- } class sub_der:public der1, der2 { -- } Soo, now sub_der would have 2 copies of base, one from der1's side and the other from der2's side. To prevent this we can have the base class ...

What is the Diamond Problem: The "diamond problem" is an ambiguity that arises when two classes B and C inherit from A, and class D inherits from both B and C. If there is a method in A that B and C have overridden, and D does not override it, then which class of the method does D inherit: that of B, or that of C?

FAQ Welcome to our diamond problem calculator, also known as a diamond problem solver. This intuitive tool allows you to enter any two numbers and the two others will appear. We've also prepared a compendium that answers all your burning questions about this topic.

Home » C programming » C programs » C program to print diamond pattern. C program to print diamond pattern. The diamond pattern in C language: This code prints a diamond pattern of stars. The diamond shape is as follows: * *** ***** *** * Diamond pattern program in C. #include <stdio.h> int main

1 Assuming the dozen compile-time errors in this code will take care of themselves? - WhozCraig Apr 12, 2022 at 5:10 A book will not be enough... he also needs a compiler. As we see the code, it was never tried to compile it. - Klaus Apr 12, 2022 at 6:15 Solve what exactly? What is the problem? - n. m. could be an AI Apr 12, 2022 at 6:16

Here, you can see that the superclass is called two times because of the diamond problem. Solution of the Diamond Problem: The solution is to use the keyword virtual on the two parent classes, ClassA and ClassB.Two-parent classes with a common base class will now inherit the base class virtually and avoid the occurrence of copies of the base class in the child class (ClassC here).

When employing numerous inheritances, a diamond problem can arise in computer languages, particularly in C++. When the code is exceedingly long, many inheritances in C++ are frequently utilized as a technique. So, in order to organize the program and the source code, we utilize classes. However, if they are not handled appropriately, multiple ...

1. Take the number of rows as input and store in the variable number. 2. The function diamondPattern prints the diamond pattern. 3. In the function diamondPattern, until the number of stars is less than equal to the argument a while loop executes which prints the spaces and stars according to the regular format. 4.

If you make a Hybrid class object in the main, you see that the Car Constructor is called two times. This is because of the diamond problem. The Hybrid class object has two copies of the Car class for each of its parents, respectively. This might not appear to be a big issue. For larger programs, however, in which the grandparent also contains ...

We can resolve the diamond problem by creating a virtual function in the base class. This function will be overridden in the derived classes, and the derived class that is called will be the one that is executed. What Is Diamond Problem And Explain With An Example? Image by: tutorialandexample.com

13 Google tells me it'susually known as the "Diamond Problem", except in the Java community, where the more drastic term is used to justify why Java "solves" the problem by disallowing it. - wolfgang Dec 15, 2011 at 9:55

What is Diamond Problem in Java In Java, the diamond problem is related to multiple inheritance. Sometimes it is also known as the deadly diamond problem or deadly diamond of death. In this section, we will learn what is the demand problem in Java and what is the solution to the diamond problem.

Philip Fong/AFP via Getty Images. Workers in Japan have started releasing treated radioactive water from the Fukushima Daiichi nuclear power plant into the Pacific Ocean. The plant was destroyed ...

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Drones and Missiles Can’t Solve America’s Drug Problem

Three decades ago, Mexican farmers could sell their corn at about $415 per ton, on average, in today’s dollars. It didn’t make for much of a living. Roughly 4 in 10 agricultural workers at the time made less than the minimum wage, equivalent to $1.40 an hour in 2023 dollars. Corn growers — just shy of a third of the total — were near the bottom of that pile.

Then Nafta came about. Over the next 15 years, Mexican tariffs on corn imported from the US came down to zero. Government price supports were withdrawn and the wholesale price of corn fell by more than half over the ensuing decade, in real terms. And what did farmers do?  Being rational agents in a market economy, many switched to more promising crops: cannabis and opium.

“The historical abandonment of the poorest farmers pushed many to plant drug crops,” said Omar García Ponce, a political scientist at George Washington University. Here’s hoping that the Republican Party comes to understand just how stupid it is to propose that the best way to interrupt the drug epidemic is to bomb them.

Lea la nota en español.

Research by García Ponce with economists Oeindrila Dube from the University of Chicago and Kevin Thom from the University of Wisconsin Milwaukee concluded that the 59% drop in the wholesale price of corn between 1990 and 2005 reduced the income of rural households in prime corn-growing municipalities by 19%.

Direct data on illegal drug production doesn’t exist. But according to the authors, the drop in corn prices led to an 8% increase in marijuana eradication and a 5% jump in opium poppy eradication in prime corn-growing areas, alongside a 16.4% increase in raw marijuana seizures and an 80% increase in the presence of drug trafficking cartels.

There is a vintage feel to these events, reminiscent of the good old days when illegal drugs didn’t kill at the first try. Yet this long ago chain of circumstances highlights the variety and complexity of the forces that shape the narcotics economy to this day, when Americans’ predilections have turned to methamphetamine and fentanyl.

Nafta’s impact on Mexican corn is hardly the only stimulant of Mexico’s emergence as a  drug-exporting powerhouse. The so-called “China Shock” that pummeled US manufacturing workers over the last quarter century or so also edged Mexican manufacturers out of the US market — encouraging Mexican workers into alternative, sometimes illicit occupations.

Economists Melissa Dell, Benjamin Feigenberg and Kensuke Teshima found that Mexican municipalities whose workers were exposed to growing competition with Chinese products in the US market between 2007 and 2010 experienced significant increases in drug-related homicides, especially if a large drug cartel was present in the area. Municipalities with cartels also experienced significant increases in cocaine seizures.

“We hypothesize,” they wrote, “that when changes in local labor market conditions make it more lucrative to transport drugs through a location by lowering the opportunity cost of criminal employment, drug trafficking organizations fight to gain control.”

The ecosystem of illicit narcotics in North America has reached another inflection point. These days it looks very little like it did in the era of “Narcos Mexico.”  The illegal marijuana trade is no longer a thing, following the legalization of weed across much of the US.

From 2009 to 2020, border seizures of marijuana fell from nearly 1,500 metric tons to around 230 tons. Between 2015 and 2020 the wholesale price of Mexican marijuana in the US dropped from about $10,000 to about $2,000 per kilo. In 2020, the Drug Enforcement Administration reported that “Mexican marijuana has largely been supplanted by domestic-produced marijuana.”

Observers report farmers in Mexico have been switching away from the crop in large numbers. Some are trying their chances in the emerging legal markets for cannabis products in Mexico. Others are leaving farming altogether and moving to cities. But most seem to be trying their luck with other cash crops, like tomatoes and chillies.

Meantime drug trafficking organizations have been moving out of marijuana and on to more lucrative and harmful synthetic drugs like methamphetamine and fentanyl. While the growth in fentanyl — ingested in many forms, often surreptitiously mixed into other drugs — is hard to estimate, the RAND corporation calculated that Americans spent about $27 billion in methamphetamine in 2016, up from $15 billion five years earlier.

It’s not clear where this will lead. But the shift to synthetics is reverberating south of the border. Rising use of meth in the US may be pinching demand for cocaine, for which it is often a subsitute. RAND’s best estimate suggests Americans spent only $24 billion on cocaine in 2016, down from $29 billion in 2011 and $58 billion in 2006.

Shifts in US consumption and policy are reorganizing the entire narcotics supply chain.  The Mexican economist Fernanda Sobrino, for instance, figured out that the 2010 reformulation of OxyContin, which made it harder to crush and dissolve the pills to release the active agent oxycodone, encouraged users in the US to shift to heroin, the illegal substitute. Heroin prices in the US increased and, surprise, heroin production in Mexico rose too.

The percentage of heroin of Mexican origin seized by the DEA increased from less than 5% in 2003 to around 90% by 2015. And, of course, violence spiked in Mexican municipalities suited to grow opium poppies as cartels moved in to take advantage of the market opportunity.

Now the force of consumer demand is pushing in the opposite direction. Americans’ embrace of fentanyl has clobbered demand for Mexican heroin. One study estimated that many farmers in Mexico’s state of Guerrero have dropped opium poppy cultivation and left rural areas, after the price of raw opium fell to some $315-$415 dollars per kilo, from over $1,000 dollars in 2017.

Some of these changes offer strands of hope. Already, violence seems to be abating in the state of Sinaloa, a narco hotspot where drug traffickers would fight over control of cannabis and poppy plantations. Human rights abuses by Mexican security forces involved in marijuana eradication are also down.

“We used to live in fear of the Army. Their eradication campaigns were brutal, and they would attack anyone near marijuana or poppy plantations,” recalled one farmer who spoke to InSight Crime for a report on the decline of Mexico’s illegal marijuana industry. “Today, our relationship with them has improved considerably.”

As traffickers drop opium and marijuana to specialize in synthetic drugs like fentanyl, their symbiotic relationship with farmer communities in rural Mexico might weaken, opening opportunities to dislodge them.

The deflation of some drug markets may make it easier to offer economic alternatives to farmers and the low-skilled men who dominate the cartels’ lower ranks — be it in the form of subsidies for alternative crops, urban employment programs or new legal avenues like, say, growing opium for the pharmaceutical industry.

Who knows how effective these efforts might be, especially as drug cartels branch out into other businesses, including human trafficking and legal crops like avocados. García Ponce notes that these sorts of interventions must be done when the drug industry is just starting. “Once criminal organizations become established it’s impossible to get them out,” he said.

What the evolution of the narcotics economy makes clear is that sending a drone with a missile across the border to blast the bad guys does nothing to alter the economic dynamics that have been driving the drug trade for half a century.

It bears remembering that the first battles of the War On Drugs were over marijuana, starting with President Richard Nixon’s order to shut down the Mexican border to dent the flow of weed in 1969. That didn’t work either. Funny how history repeats itself.

Elsewhere in Bloomberg Opinion:

• Fentanyl and Politics Are Toxic 2024 Mix for US and Mexico: Eduardo Porter

• America’s Export of Gun Violence Is a Bipartisan Outrage: Michael R. Bloomberg

• Mexico’s Democracy Is Crumbling Under AMLO: Shannon O’Neil

For more Bloomberg Opinion, subscribe to our newsletter.

(Corrects affiliation of Omar García Ponce in third paragraph.)

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Eduardo Porter is a Bloomberg Opinion columnist covering Latin America, US economic policy and immigration. He is the author of “American Poison: How Racial Hostility Destroyed Our Promise” and “The Price of Everything: Finding Method in the Madness of What Things Cost.”

More stories like this are available on bloomberg.com/opinion

©2023 Bloomberg L.P.

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International Edition

Diamond Problem in C++ Programming

The Diamond Problem is a multiple inheritance When we inherit more than one base class in the same derived class and all these base classes also inherit another but same single class (super parent), multiple references of the super parent class become available to the derived class. So, it becomes unclear to the derived class, which version of the super parent class it should refer to.

The given program demonstrates the concept of the "diamond problem" in C++ programming using multiple inheritance and virtual base class. Let's understand it step by step:

  • First, we define a class A with a public member function display() that simply prints the message "Display Method in A" to the console.
  • Next, we define a class B that is derived from class A using virtual inheritance. Class B has a public member function show() that simply prints the message "Show Method in B" to the console.
  • Then, we define a class C that is also derived from class A using virtual inheritance.
  • Finally, we define a class D that is derived from both classes B and C . Class D does not have any additional members or methods.
  • In the main function, we create an object of class D and call the display() method of class A using the object. Since class B and class C both virtually inherit from class A , the display() method of class A is only included once in the inheritance hierarchy, even though it is inherited by both class B and class C .
  • Thus, the output of the program will be "Display Method in A" when we call the display() method of class A using the D object o .

Source Code

Program list.

  • C++ Introduction
  • Hello World In C++
  • Why we using namespace std in C++
  • Getting Inputs in C++
  • std::string class in C++
  • if Statement in C++
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  • else if Statement in C++
  • Nested if Statement in C++
  • Switch Statement in C++
  • Group Switch Statement in C++
  • Salary Calculation using IF Statement in C++
  • Insurance Eligibility Status using C++
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  • do While Loop in C++
  • For Loop in C++
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  • Sum of N Numbers in C++
  • Factors of a Given Number using C++
  • Armstrong Number using C++
  • Prime Number using C++
  • Arrays in C++
  • Search an Element in an array in C++
  • Sum of Elements in an array in C++
  • Greatest Elements in an array in C++
  • Sort Elements in an array in C++
  • Function In C++
  • Function Overloading In C++
  • Default Argument Function In C++
  • Template In C++
  • Enum In C++
  • Class in C++
  • What is Public Access Specifier in C++
  • What is Private Access Specifier in C++
  • Scope Resolution :: Operator in C++
  • Default Constructor in C++
  • Parametrized Constructor in C++
  • Copy Constructor in C++
  • Constructor Overloading in C++
  • Destructor Overloading in C++
  • Single Inheritance in C++
  • Multiple Inheritance in C++
  • Multilevel Inheritance in C++
  • Hybrid Inheritance in C++
  • Hierarchical Inheritance in C++
  • Diamond Problem in C++
  • Diamond Problem using Constructor in C++
  • Bank Management System using Class & inheritance in C++
  • What is Protected Access Specifier in C++
  • Function Overriding in C++
  • Operator Overloading in C++
  • Unary Operator Overloading in C++
  • Base Class Pointer derived Class Object in C++
  • Virtual Function in C++
  • Sample Virtual Function in C++
  • Pure Virtual Function & Abstract Class in C++
  • What is Abstraction in C++
  • Getter & Setter , this Keyword in C++
  • Static variables and Static Function in C++
  • Friend Function in C++
  • Friend Class in C++
  • Change Private Values Using Friend Class in C++
  • Single Value Member Initializer List in C++
  • Multiple Value Member Initializer List in C++
  • Add value to Base Class Constructor Using Member Initializer List in C++
  • Initialized Const variable using Member Initializer List in C++
  • Constructor’s parameter name is same as data member using Member Initializer List in C++
  • Narrowing conversion Problem in Member Initializer in C++
  • inline Function in C++
  • Lambda Expressions/Functions in C++
  • Preprocessor Directive in C++
  • Character Classification Functions in C++
  • rand() in C++
  • Exception Handling in C++
  • Write a File using C++ fstream
  • Read a File using C++ fstream
  • STL-Array in C++
  • STL-Vector in C++
  • STL-deque in C++
  • STL-List in C++
  • STL-Stack in C++

Flow Control

  • Hello World
  • Input From User in C++
  • Arithmetic Operators in C++
  • Assignment Operators in C++
  • Comparison Operators in C++
  • Logical Operators in C++
  • Math Functions in C++

IF Statement Examples

  • If Statement in C++
  • If-Else Statement in C++
  • If-Else-If Statement in C++

Switch Case

  • Basic Switch Case Example
  • Calculator using Switch Case
  • Present Elevator Position in C++
  • Hotel Management in C++
  • Display Month in C++
  • Find Vowels in C++
  • Find Weekend in C++
  • Find Weekdays in C++

Goto Statement

  • Factorial using Goto in C++
  • Printing Even Numbers using Goto
  • Printing Given Word using Goto
  • Printing Numbers using Goto
  • Printing Odd Numbers using Goto
  • Sum of Numbers using Goto
  • Print Tables using Goto
  • Print Reverse Tables using Goto

Break and Continue

  • Printing Numbers in C++
  • Printing Continues Numbers in C++
  • Armstrong Number using While Loop
  • Decimal to Binary in C++
  • Printing Even & Odd Numbers
  • Printing Positive & Negative Numbers
  • Prime between two Numbers
  • Find Prime or Composite
  • Tables using While Loop
  • Reverse Tables using While Loop

Do While Loop

  • Printing Array using Do While Loop
  • Printing given Word
  • Printing Numbers using Do While Loop
  • Sum of Numbers using For Loop
  • Sum of Two Square using For Loop
  • Alphabet Diamond Pattern
  • Armstrong number using For Loop
  • Cubic Numbers using For Loop
  • Divisible by 7 using For Loop
  • Fibonacci series using For Loop
  • Formula Examples using For Loop
  • Reverse Number Pattern
  • Number Patterns using For Loop
  • Odd & Even Numbers using For Loop
  • Printing Star Diamond Pattern in C++
  • Printing Flag Pattern in C++
  • Printing Pyramid Pattern in C++
  • Printing Boat Pattern in C++
  • Diamond Pattern Outline in C++
  • Square Pattern Outline in C++
  • Triangle Pattern Outline in C++
  • Printing Tables using For Loop
  • Reverse table using For Loop
  • Sum of Even & Odd using For Loop
  • Squaring Numbers using For Loop
  • Reverse Printing Number using in C++
  • Prime or Composite using For Loop
  • Common Patten Examples in C++
  • Basic Friend Function Example
  • Addition using Friend Function
  • Character Integer using Friend Function
  • Find Distance using Friend Function
  • Length of Box using Friend Function
  • Private & Protected Example in C++

String Examples

  • Basic Example of String in C++
  • Addition using String
  • String Append in C++
  • String Capacity Function in C++
  • String Character Change in C++
  • String Concatenation in C++
  • String Input Getline in C++
  • String Length in C++
  • String Palindrome in C++
  • Remove Duplicate String in C++
  • String Resize in C++
  • String Reverse without using Function
  • Sentence Case Example using String
  • Swapping String in C++

Array Examples

  • Display Marks using Array
  • Find Largest Number using Array
  • Find Second Largest Number using Array
  • Find Second Smallest Number using Array
  • Find Smallest Number using Array
  • Print Values using Array
  • Print Array Values using While Loop
  • Sum of Array Average using Array
  • Transpose Matrix using Array
  • Two Dimensional Array Addition
  • Array Addition using Class Function
  • Two Dimensional Array Subtraction
  • Three Dimensional Array Example

Structure Examples

  • Area of Rectangle using Structure
  • Book Information using Structure
  • Person Information using Structure
  • Student Information using Structure

Structure & Pointer Examples

  • Basic Example of Structure & Pointer
  • Show Book Details in C++
  • Find Length in C++

Structure & Functions Examples

  • Area of Rectangle in C++
  • Show Book Information in C++
  • Show Person Information in C++

Enumeration Examples

  • Direction Example in C++
  • Week Days Example in C++

Template Examples

  • Addition using Template
  • Data Types Example using Template
  • Hello World using Function
  • Call by Value & Reference in C++
  • Function Overloading in C++
  • Function Parameter Examples in C++
  • Function Recursion Example in C++
  • Arithmetic Operators using Function in C++
  • Sum of two Numbers in C++
  • Difference between two Numbers in C++
  • Division of two Numbers in C++
  • Product of two Numbers in C++
  • Check Prime Number using Function
  • Tables using Function in C++
  • Update Function in C++
  • Display Marksheet using Function in C++
  • Function with Argument Examples in C++

Inheritance Examples

Hierarchical inheritance.

  • Basic Example of Hierarchical
  • Area of Rectangle Example

Hybrid Inheritance

  • Multiplication using Hybrid Inheritance

Multilevel Inheritance

  • Basic Example of Multilevel Inheritance
  • Eat Sleep Code Example

Multiple Inheritance

  • Basic Example of Multiple Inheritance
  • Addition using Multiple Inheritance

Single Level Inheritance

  • Basic Example of Single Level Inheritance
  • Eating Coding Program
  • Print Salary Bonus Example in C++
  • Multiplication using Single Level Inheritance

Class and Objects

  • Find Box Volume using Objects
  • Class and Object Example in C++
  • Object Creation Example in C++
  • Basic Example of Multiple Objects

Constructor Example

  • Area of Rectangle using Constructor
  • Constructor Overloading Example
  • Constructor Invoking Example
  • Constructor Deep Copy Example
  • Copy Constructor Basic Example
  • Copy Constructor Shallow Copy
  • Parameterized Constructor Example

Destructor Example

  • Destructor Example in C++
  • Operator Overloading Example
  • Assignment Operator Overloading Example
  • Binary Operator Example
  • Increment & Decrement Example
  • Input & Output Example
  • Relational Operator Distance Example
  • Distance Measuring using Unary Operator

Operator and Function Example

  • Display Values using Friend Function

List of Programs

  • Classes Example in C++
  • Pointer to Classes in C++
  • Data Hiding in C++
  • Constructor Example in C++
  • Scope Example in C++
  • Inline Function in C++
  • Struct vs Class in C++
  • Insertion Overload in C++
  • Inheritance Example in C++
  • Access Specifier in C++
  • Runtime Polymorphism in C++
  • Abstract Class in C++
  • Static Member in C++
  • Static Member Function in C++
  • Nested or InnerClass in C++
  • Dynamic Heap in C++
  • Try Catch in C++
  • Try Catch Function in C++
  • More About Catch in C++
  • Template in C++
  • Template Class in C++

Pointer Examples

  • Basic Example of Pointer in C++
  • This Pointer Example in C++
  • Null Pointer Example in C++

Memory Management Examples

  • Dynamic Memory Allocation Example
  • Creation & Deletion Array Example

Pointers and Arrays

  • Basic Example of Pointer & Array
  • Print Character using Pointer & Array
  • Print Floating Values Example in C++
  • Print Array Values Example in C++

Virtual Function Examples

  • Basic Example of Virtual Function
  • Load Features Example in C++

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  1. What is Diamond Problem in C# ~ Programming With Shri

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  2. C++ Diamond problem in OOPS, Solution using Virtual Inheritance with Example

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  3. Multiple Inheritance in C++

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  4. What is Diamond Problem in C# ~ Programming With Shri

    solve diamond problem in c

  5. What is Diamond Problem in C# ~ Programming With Shri

    solve diamond problem in c

  6. Diamond Problem In C++

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VIDEO

  1. hybrid Inheritance using c++|hybrid Inheritance using java|#coding #c #shorts |what is Inheritance

  2. C++ leetcode 32. Longest Valid Parentheses

  3. Diamond Problem

  4. half 💪diamond 🔥shape pattern in c 💯 #programming #coding #coder

  5. Diamond Problem and its Solution in C++?

  6. Diamond pattern in c++ #shorts #coding #cprogramming #computerprogramming #computerscience #coder

COMMENTS

  1. What Is the Diamond Problem in C++? How to Spot It and How to Fix It

    Published Aug 25, 2021 The Diamond Problem can arise in C++ when you use multiple inheritance. Here's what it is, how to spot it, and how to fix it. Readers like you help support MUO. When you make a purchase using links on our site, we may earn an affiliate commission. Read More.

  2. oop

    19.9k 19 58 71 what language are you asking about? - anon Jan 14, 2010 at 14:49 10 @Neil Butterworth language should not matter in this as this is more a concept issue. Languages like C++ allow this but Java and C# does not. - Vincent Ramdhanie Jan 14, 2010 at 14:50 And this is why "multiple inheritance" is a dirty word... - Danail

  3. Diamond Problem in C++

    What is the Diamond Inheritance Problem in C++? The following image illustrates the situation under which the Diamond problem occurs. The Class A, is inherited by both Class B and C. Then Class D performs multiple inheritance by inheriting both B and C. Now why does this cause a problem?

  4. Virtual Inheritance in C++, and solving the diamond problem

    Solving the Diamond Problem with Virtual Inheritance By Andrei Milea Multiple inheritance in C++ is a powerful, but tricky tool, that often leads to problems if not used carefully. This article will teach you how to use virtual inheritance to solve some of these common problems programmers run into.

  5. Multiple Inheritance in C++ and the Diamond Problem

    What if Reptile class overrides the breathe () method? The Snake class would not know which breathe () method to call. This is the "Diamond Problem". Diamond Problem Look at the code below. It is like the code in the example above, except that we have overridden the breathe () method in the Reptile class. If you try compiling the program, it won't.

  6. Multiple Inheritance in C++

    Practice Video Multiple Inheritance is a feature of C++ where a class can inherit from more than one classes. The constructors of inherited classes are called in the same order in which they are inherited. For example, in the following program, B's constructor is called before A's constructor. A class can be derived from more than one base class.

  7. How does the compiler internally solve the diamond problem in C++?

    How does the compiler internally solve the diamond problem in C++? Ask Question Asked 11 years, 11 months ago Modified 11 months ago Viewed 3k times 11 We know that we can solve the diamond problem using virtual inheritance. For example:

  8. How to solve diamond issue in C++?

    Any solution to this? c++ inheritance name-collision Share Improve this question Follow edited Jul 26, 2017 at 7:38 Jarod42 202k 14 178 299 asked Jul 26, 2017 at 6:25 BSalunke 11.5k 8 34 68 11 There's no diamond here. You just have a name clash from two unrelated base classes, and virtual inheritance cannot do anything about that.

  9. C++: Diamond Problem and Virtual Inheritance

    What is the Diamond Problem? When we inherit more than one base class in the same derived class and all these base classes also inherit another but same single class (super parent), multiple references of the super parent class become available to the derived class.

  10. C++ Solving Diamond Inheritance Without Virtual Inheritance

    47 1 13 I only get a warning not an error. Can you give us the actual compiler error you are getting or post code that reproduces the problem. BTW it isn't a diamond if you don't use virtual inheritance. Virtual inheritance is what merges the two bases into one creating the diamond shape if you draw it in a diagram. - Eelke Jul 6, 2017 at 6:13

  11. Multiple Inheritance in C++

    Multiple Inheritance is the concept of inheritance in C++ by which we can inherit data members and member functions from multiple (more than one) base/parent class (es) so that the derived class can have properties from more than one parent class.

  12. What Is the Diamond Problem in C++? How to Spot It and How to Fix It

    There are several ways to fix the diamond problem in C++. One solution is to use virtual inheritance, which ensures that only one instance of the base class is created in the derived class hierarchy. This eliminates the ambiguity and conflicts that arise in the diamond problem.

  13. Diamond Problem in C++

    The Diamond Problem: When two super classes of a class share a base class, the diamond issue arises. For instance, in the diagram below, the TA class receives two copies of every attribute from the Person class, which results in ambiguities. Think about the following program, for instance. # include < iostream >.

  14. c++

    1 Assuming the dozen compile-time errors in this code will take care of themselves? - WhozCraig Apr 12, 2022 at 5:10 A book will not be enough... he also needs a compiler. As we see the code, it was never tried to compile it. - Klaus Apr 12, 2022 at 6:15 Solve what exactly? What is the problem? - n. m. could be an AI Apr 12, 2022 at 6:16

  15. how can we solve diamond problem in c

    The six steps of problem solving involve problem definition, problem analysis, developing possible solutions, selecting a solution, implementing the solution and evaluating the outcome. Problem solving models are used to address issues that..... Maytag washers are reliable and durable machines, but like any appliance, they can experience problems from time to time.

  16. Diamond Problem In C++

    JOIN MEYouTube 🎬 https://www.youtube.com/channel/UCs6sf4iRhhE875T1QjG3wPQ/joinPatreon 🚀 https://www.patreon.com/cppnutsIn this video we will see very fam...

  17. C++ Diamond problem in OOPS, Solution using Virtual ...

    In this c++ OOPS Video tutorial for Beginners, you will learn about the diamond problem and discusses how to solve that problem using virtual inheritance.Vis...

  18. Hybrid inheritance in C++

    Hybrid inheritance is a combination of multiple inheritance and multilevel inheritance. A class is derived from two classes as in multiple inheritance. Howev...

  19. Diamond Problem using Constructor in C++ Programming

    Let's understand it step by step: First, we define a class A with a public integer variable x and a constructor that prints the message "Constructing A" to the console when an object of class A is created. Next, we define a class B that is derived from class A using virtual inheritance. Class B has a constructor that prints the message ...

  20. The Diamond Problem In Computer Programming

    November 27, 2022 by July. In computer programming, the diamond problem is an inheritance ambiguity that can arise when two classes B and C inherit from a superclass A, and class D inherits from both B and C. If there is a method in A that B and C have overridden, and D does not override it, then which version of the method does D inherit: that ...

  21. Drones and Missiles Can't Solve America's Drug Problem

    September 12, 2023 at 7:37 a.m. EDT. Three decades ago, Mexican farmers could sell their corn at about $415 per ton, on average, in today's dollars. It didn't make for much of a living ...

  22. How to solve your million pound pension problem

    In the March Budget, chancellor Jeremy Hunt made the surprise move to scrap the LTA — then set at £1,073,100 — in a bid to stop highly paid NHS doctors taking early retirement to avoid tax ...

  23. Diamond Problem in C++ Programming

    Diamond Problem in C++ Programming. The Diamond Problem is a multiple inheritance When we inherit more than one base class in the same derived class and all these base classes also inherit another but same single class (super parent), multiple references of the super parent class become available to the derived class.