Exceptional C++ Style 40 New Engineering Puzzles, Programming Problems, and Solutions

Chapter 1. Uses and Abuses of vector

Difficulty: 4

Almost everybody uses std::vector, and that's good. Unfortunately, many people misunderstand some of its semantics and end up unwittingly using it in surprising and dangerous ways. How many of the subtle problems illustrated in this Item might be lurking in your current program?

JG Question

1. Given a vector<int> v, what is the difference between the lines marked A and B?

   void f(vector<int>& v) {
    v[0];       // A
    v.at(0);    // B
   }
   

Guru Question

1. Consider the following code:

    vector<int> v; v.reserve(2); assert(v.capacity() == 2); v[0] = 1; v[1] = 2; for(vector<int>::iterator i = v.begin(); i < v.end(); i++) { cout << *i << endl; } cout << v[0]; v.reserve(100); assert(v.capacity() == 100); cout << v[0]; v[2] = ...