C++ Primer, Fifth Edition

4.6. The Member Access Operators

The dot (§ 1.5.2, p. 23) and arrow (§ 3.4.1, p. 110) operators provide for member access. The dot operator fetches a member from an object of class type; arrow is defined so that ptr->mem is a synonym for (*ptr).mem:

string s1 = "a string", *p = &s1;auto n = s1.size(); // run the size member of the string s1n = (*p).size();    // run size on the object to which p pointsn = p->size();      // equivalent to (*p).size()

Because dereference has a lower precedence than dot, we must parenthesize the dereference subexpression. If we omit the parentheses, this code means something quite different:

// run the size member of p, then dereference the result!*p.size();    // error: p is a pointer and has no member named