Linxutopia - Thinking in C++ - 4: Data Abstraction

Thinking in C++
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Global scope resolution

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The scope resolution operator gets you out of situations in which the name the compiler chooses by default (the “nearest” name) isn’t what you want. For example, suppose you have a structure with a local identifier a, and you want to select a global identifier a from inside a member function. The compiler would default to choosing the local one, so you must tell it to do otherwise. When you want to specify a global name using scope resolution, you use the operator with nothing in front of it. Here’s an example that shows global scope resolution for both a variable and a function:

//: C04:Scoperes.cpp
// Global scope resolution
int a;
void f() {}

struct S {
  int a;
  void f();
};

void S::f() {
  ::f();  // Would be recursive otherwise!
  ::a++;  // Select the global a
  a--;    // The a at struct scope
}
int main() { S s; f(); } ///:~

Without scope resolution in S::f( ), the compiler would default to selecting the member versions of f( ) and a.

Thinking in C++
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