C++ Tutorial => Result of some pointer comparisons

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Example

If two pointers are compared using <, >, <=, or >=, the result is unspecified in the following cases:

The pointers point into different arrays. (A non-array object is considered an array of size 1.)

int x;
int y;
const bool b1 = &x < &y;            // unspecified
int a[10];
const bool b2 = &a[0] < &a[1];      // true
const bool b3 = &a[0] < &x;         // unspecified
const bool b4 = (a + 9) < (a + 10); // true
                                    // note: a+10 points past the end of the array

The pointers point into the same object, but to members with different access control.

class A {
  public:
    int x;
    int y;
    bool f1() { return &x < &y; } // true; x comes before y
    bool f2() { return &x < &z; } // unspecified
  private:
    int z;
};

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