I wrote a class in C++. In it I wrote:
class Node{
private:
Node*m[200]=NULL;
};
(This is a part of the class) But I receive errors. What should I do for defining an array of pointers, NULL ?
3 Answers
To make all 200 pointers be null, write:
class Node
{
Node *m[200] = {};
};
This is only valid in C++11 and later.
13 Comments
M.M
Not sure if this was possible prior to C++11
Amir Havangi
2.cpp:6:14: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default] Node*m[200]={}; ^ 2.cpp:6:14: warning: extended initializer lists only available with -std=c++11 or -std=gnu++11 [enabled by default]
M.M
@AmirHavangi do as the error message says, and use
-std=c++11 or -std=gnu++11
flogram_dev
{ 0 } for pre-C++11.M.M
@Pradhan I'm pretty sure that all inline braced-initializers are invalid before C++11 (your clang may be implementing an extension); what I meant was that I can't think of an alternative means of achieving the same initialization
|
For completeness, if you don't have C++11 support, you can value initialize the array in a constructor. This has the effect of zero initializing the elements:
class Node
{
public:
Node() : m() {}
private:
Node* m[200];
};
Note also that value initializing instances of the original Node has the same effect WRT zero initializing the elements:
Node n = {}; // Node must be aggregate, as in original code.
Comments
Since you're writing C++, I'd recommend avoiding raw arrays and using std::vector instead (or std::array if you have C++11).
In pre-C++11 you need initialize your members in the constructor:
class Node
{
public:
Node() : m(200) {}
private:
std::vector<Node*> m;
};
This will initialize m to hold 200 null pointers when you construct a Node.
NULLis for pointers, not arrays. It makes no sense to initialize an array withNULL.Node* m[200]{};. But even better, usestd::vectorinstead.