creating methods that doesn't depend on a object
//functions.h

namespace MyFunctions
{
   void foo();
   void goo();
}

//functions.cpp

namespace MyFunctions
{
   void foo() {}
   void goo() {}
}

//functions.h
inline void foo() {
    //..
}
inline void goo() {
    //..
}

//fileThatUsesFunctions.cpp

namespace
{
    void foo() {}
    void goo() {}
}

namespace Utils
{
   void myMethod();
}

namespace Utils
{
  void myMethod()
  {
    //Implementation
  }
}

namespace Foo
{
    publicFunction1();
    publicFunction2();

    namespace
    {
        privateFunction1();
        std::vector<Bar> privateData;
    }
}

// MyFile.h
int some_function();

// MyFile.cpp

int some_function() {
  return 42;
}

// MyFile.h
namespace MyNamespace {
  int some_function();
}

// MyFile.cpp
using MyNamespace;
int some_function() {
  return 42;
}