C++ random question

test

RandomNumberGenerator rng;
cout << rng() << endl;

header

class RandomNumberGenerator {
public:
    unsigned long operator()(); 
};

cpp

unsigned long operator()() {   // HERE IS ERROR
srand(time(NULL));
unsigned long r = rand();
return r;
}

basically im trying to do a random number generator. but getting an error :

开发者_如何学PythonC:\CodeBlocks\kool\praks3\src\myfunctors.cpp|5|error: 'long unsigned int operator()()' must be a nonstatic member function|

---

You need to tell the compiler that the operator()() belongs in the RandomNumberGenerator class by using :::

unsigned long RandomNumberGenerator::operator()()
{
    srand(time(NULL));
    unsigned long r = rand();
    return r;
}

The compiler says that it "must be a nonstatic member function" because operator()() is required to be a member of a class and not a global function. And without the scoping operator the compiler thinks that the operator()() is a global function and thus not a member of RandomNumberGenerator, which is the source of the error.

Don't forget to include the header for the RandomNumberGenerator class into the source file!

---

Outside the class, this is how you've to define the operator():

unsigned long RandomNumberGenerator::operator()() {
  //note this ^^^^^^^^^^^^^^^^^^^^^^^
   srand(time(NULL));
   unsigned long r = rand();
   return r;
}

The part RandomNumberGenerator:: tells the compiler that operator() belongs to the class RandomNumberGenerator.

---

You are not scoping your operator.

Try this:

unsigned long RandomNumberGenerator::operator()() {
    srand(time(NULL));
    unsigned long r = rand();
    return r;
}

Regards,
Dennis M.

---

You forgot to specify the scope, try unsigned long RandomNumberGenerator :: operator()() The point is, how should the compiler otherwise know to which class your operator() belongs to?