Why is the Scope Resolution Operator (::) Essential in C ?

Why Does C Utilize the Scope Resolution Operator (::)?

Unlike Java, C employs the scope resolution operator (::) as a distinct symbol. This operator serves a specific purpose in disambiguating code syntax.

Originally, the rationale behind :: stemmed from the need to accommodate code structures like:

struct foo
{
  int blah;
};

struct thingy
{
  int data;
};

struct bar : public foo
{
  thingy foo;
};

int main()
{
  bar test;
  test.foo.data = 5;
  test.foo::blah = 10;
  return 0;
}

In this example, the '.' operator would have caused ambiguity, as both "foo" represent different entities (a member variable and a derived class type). To address this, the use of :: for class access and '.' for member access was introduced.

By utilizing a distinct operator, C ensures that the compiler can unambiguously determine the context (object or typename/namespace) in which the identifier is used. This differentiation allows for syntax like the following:

foo::bar; // Class access
thing.baz; // Member access

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