CS253 IQ 11

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Which of these is a valid declaration?

1. template <int I, typename T = long double>
class Foo { };
2. template <class C, long L, bool B = false>
class Foo { };
3. template <int *IP> class Foo { };
4. All of the above
5. template <double D> class Foo { };

Everything but double D. You can pass double as a type, but not as a value.

Front/back

What will this code emit?

vector<int> v = {2,3,5,7};
for (auto it = v.front(); it != v.back(); ++it)
    cout << it;

23456

1. 235
2. 2357
3. 23456
4. 234567
5. None of the above

.front() and .back() return references to values, not iterators.

Subtraction

What will this code emit?

vector<int> v = {1,2,3};
cout << v.end() - v.begin() << endl;

3

1. 123
2. 2
3. 3
4. Depends on the size of an int.
5. It will not compile.

v.end() “points” one past the last element, not to last element.

Traversal #1

What will this code emit?

set<int> s = {2,4,1,3};
for (auto it = s.begin(); it < s.end(); ++it)
    cout << *it;

c.cc:2: error: no match for 'operator<' in 'it < s.std::set<int>::end()' 
   (operand types are 'std::_Rb_tree_const_iterator<int>' and 
   'std::set<int>::iterator' {aka 'std::_Rb_tree_const_iterator<int>'})

1. 2413
2. 1234
3. 123
4. It depends on where the tree nodes are allocated.
5. None of the above.

You can’t use < on a set::iterator

Traversal #2

What will this code emit?

set<int> s = {2,4,1,3};
for (auto it = s.begin(); it != s.end(); ++it)
    cout << *it;

1234

1. 2413
2. 1234
3. 123
4. It depends on where the tree nodes are allocated.
5. None of the above.

Sets are sorted.