Question

I have couple questions regarding some C++ rules.

1. Why am I able to call a function/method from outside the class in the namespace when I include the return type? (look at the namespace test2::testclass2 in the code below) i.e. this works:

   bool b = testclass1::foo<int>(2);
   

   whereas this doesn’t: – (it doesn’t even compile – compiler throws that this is function redeclaration)

   testclass1::foo<int>(2);
   

   C++ complains that it is a function redeclaration. Is that so?

2. This line:

   bool b = testclass1::foo<int>(2);
   

   gets called first before anything else. Is this because static methods get created always first before anything else in C++?

3. Where can I find those rules? I have a few C++ books at home, so if someone would be kind enough to either point out a book (and chapter or page) or direct me to a website I would greatly appreciate it.

Here below is the sample (partial) code that I tested at home with Visual Studio 2008:

class testclass1
    {
    public:
        testclass1(void);
        ~testclass1(void);

        template<class A> static bool foo(int i)
        {
            std::cout <<"in static foo";    
            return true;
        }
    };


namespace test2
{
    class testclass2
    {
    public:
        testclass2(void);
        ~testclass2(void);
    };

    bool b = testclass1::foo<int>(2);
}

EDIT:

A few people mentioned that I need to call this inside the function and this will work without any problem.
I understand that; the only reason I asked this question is because I saw this code somewhere (in someone’s elses project) and was wondering how and why this works. Since I never really seen anyone doing it before.

Also, this is used (in multiple places) as a way to call and instantiate a large number of classes like this via those function calls (that are outside). They get called first before anything else is instantiated.

Answer 1

C++ is not Python. You write statements in functions and execution starts from the main method. The reason bool b = ... happens to work is that it’s defining the global variable b and the function call is merely the initialization expression.

Definitions can exist outside functions while other statements can only exist inside a function body.