结构C ++表示卡住

Question

This is really question on C++ language, what does SNeuron(int NumInputs); mean inside the structure? I'm not c++ programer and this construction inside structure looks strange to me. Can anybody explain it what it could be for? I already tried google.

 struct SNeuron
    {
       //the number of inputs into the neuron
       int m_NumInputs;

       //the weights for each input
       vector<double> m_vecWeight;

       //ctor
       SNeuron(int NumInputs);
    };

Answer 1

A struct in C++ is exactly the same as a class, except that all members of a struct are public by default.

So what you are seeing here is simply a constructor declaration for the struct.

The reason, I believe, is to make interoperability with C easier.

Answer 2

It's simply declaring a constructor for the struct SNeuron. This is called a prototype method, and won't wok unless it's implemented later on. It could be implemented inside the class by saying

SNeuron(int NumInputs) {
    // Constructor code
}

or outside like this:

SNeuron::SNeuron(int NumInputs) {
    // Constructor code
}

The main use of this would be to initialize the fields m_NumInputs and m_vecWeight.

Answer 3

When an instance of the structure is created, it need to be "constructed" (ie initialized), that is done by having constructor functions, which are automatically called by the compiler when an instance is created.

For example, in the following declaration and definition of a variable using the structure, the constructor will be called:

SNeuron myNeuron(5);  // Creates the instance and calls the constructor function

Answer 4

That is simply a constructor. A constructor is basically a mechanism by which you initialize all the data members of a class when an object of that class type is created.

You can write constructors for both struct and class. But that constructor which you declared in your code is not the default constructor because a default constructor is that constructor which takes no arguments.