class A {
private:
  static const int a = 4;
  /*...*/
};

class A{
private:
 static const int a = 4; // valid
 static const std::string t ; // can't be initialized here
 ...
 ...
};


// in a cpp file where the static variable will exist
const std::string A::t = "this way it works";

class X
{
public:
      static int i;
};
int X::i = 0; // definition outside class declaration

class C {
      static int i;
      static int j;
      static int k;
      static int l;
      static int m;
      static int n;
      static int p;
      static int q;
      static int r;
      static int s;
      static int f() { return 0; }
      int a;
public:
      C() { a = 0; }
      };

C c;
int C::i = C::f();    // initialize with static member function
int C::j = C::i;      // initialize with another static data member
int C::k = c.f();     // initialize with member function from an object
int C::l = c.j;       // initialize with data member from an object
int C::s = c.a;       // initialize with nonstatic data member
int C::r = 1;         // initialize with a constant value

class Y : private C {} y;

int C::m = Y::f();
int C::n = Y::r;
int C::p = y.r;       // error
int C::q = y.f();     // error

#include <iostream>
using namespace std;

struct X {
  static const int a = 76;
};

const int X::a;

int main() {
  cout << X::a << endl;
}

template<class T> struct X{
   static T x;
};

template<class T> T X<T>::x = T();

int main(){
   X<int> x;
}

// .h
class A{
private:
 static const int a = 4;
 static const foo bar;
 ...
 ...
};

// .cpp
const foo A::bar = ...;

class Entry {
public:
   int x;
   Entry(v):x(v){}
}

struct Type {
   static constexpr Entry GetEntry() { return Entry(10); }
};