What’s new and why we should care

1. C++ 11 Features
What’s new and why we should care
(slightly updated presentation)

2. (Very) brief history of C++
1979: Bjarne Stroustrup starts “C with
Classes”
Classes, few other things
1983: Renamed to C++
virtual functions, references, new/delete, ...
1998: ISO C++98
First ISO standard

3. (Very) brief history of C++
2003: C++03
“Bug fixes”
2011: C++11
In the works for almost 10 years
Lots of new language / standard library features
Most of it supported by all big compilers by now
(VS2012, g++4.8, clang 3.3, Intel 13.0)

4. (Very) brief future of C++
2014: C++14
“Bug fixes”
Small improvements
Starting to be picked up by compilers
2017: C++17
More functionality
Largely undefined

5. Right angle bracket
C++
std::map<std::string, std::vector<int> > map;
C++11
std::map<std::string, std::vector<int>> map;

6. auto
auto i = 42; // i is an int
auto l = 42LL; // l is an long long
auto p = new foo(); // p is a foo*

7. auto pointers?
int* foo();
// pointer picked up, can be added anyway
auto p_bar = foo(); // int*
auto *p_baz = foo(); // int*

8. auto references?
int& foo();
auto bar = foo(); // int& or int?

9. auto references?
int& foo();
auto bar = foo(); // int& or int?
// reference *not* picked up
auto bar = foo(); // int
auto& baz = foo(); // int&

10. auto constness?
const auto foo();
// constness *not* picked up
auto bar = foo(); // Abc
const auto baz = foo(); // const Abc

11. auto constness + reference?
const int& foo();
auto &bar = foo(); // int& ... ?
bar = 3; // Writing to const variable ... ?

12. auto constness + reference?
const int& foo();
auto &bar = foo(); // int& ... ?
bar = 3; // Writing to const variable ... ?
// Special case, const picked up when const + reference!
auto &bar = foo(); // const int&
bar = 3; // Compiler error!

13. auto, general rule:
Private, writable
auto foo = bar();
Private, not writable:
const auto foo = bar();
Shared, not writable:
const auto &foo = bar();
Shared, writable
auto &foo = bar();
if return value requires copy: same as private

14. auto
C++
std::map<std::string, std::vector<int>> map;
std::map<std::string, std::vector<int>>::iterator it = map.begin();
for(it; it != map.end(); ++it)
{
}
C++11
std::map<std::string, std::vector<int>> map;
auto it = map.begin();
for(it; it != map.end(); ++it)
{
}

15. Range-based for loops
C++
std::map<std::string, std::vector<int>> map;
std::map<std::string, std::vector<int>>::iterator it = map.begin();
for(it; it != map.end(); ++it)
{
}
C++11
// auto& or const auto& would be more efficient!
std::map<std::string, std::vector<int>> map;
for (auto element : map)
{
}

16. Range-based for loops
int my_array[5] = {1, 2, 3, 4, 5};
// double the value of each element in my_array:
for (int &x : my_array) {
x *= 2;
}
std::vector<int> foo;
for(int element : foo)
{
}

17. nullptr
void foo(int* p) {}
void bar(std::shared_ptr<int> p) {}
int* p1 = NULL;
int* p2 = nullptr;
if(p1 == p2)
{
}
foo(nullptr);
bar(nullptr);
bool f = nullptr;
int i = nullptr; // error: A native nullptr can only be converted
to bool or, using reinterpret_cast, to an integral type
void f(int); //#1
void f(char *);//#2
//C++03
f(0); //which f is called?
//C++11
f(nullptr) //unambiguous, calls #2

18. Override and final
class B
{
public:
virtual void f(short) {std::cout << "B::f" << std::endl;}
};
class D : public B
{
public:
virtual void f(int) {std::cout << "D::f" << std::endl;}
};

19. Override and final
class B
{
public:
virtual void f(int) const {std::cout << "B::f " << std::endl;}
};
class D : public B
{
public:
virtual void f(int) {std::cout << "D::f" << std::endl;}
};

20. Override and final
class B
{
public:
virtual void f(short) {std::cout << "B::f" << std::endl;}
};
class D : public B
{
public:
virtual void f(int) override {std::cout << "D::f" << std::endl;}
};

21. Override and final
class B
{
public:
virtual void f(short) {std::cout << "B::f" << std::endl;}
};
class D : public B
{
public:
virtual void f(int) final {std::cout << "D::f" << std::endl;}
};

22. Strongly-typed enums
enum class Options {None, One, All};
Options o = Options::All;
Type safe
int i = Options::All; // Compiler error!
Scoped
Options o = All; // Compiler error
User-specified underlying type
enum Enum3 : unsigned long {Val1 = 1, Val2};

23. Smart Pointers
boost::shared_ptr -> std::shared_ptr
boost::unique_ptr -> std::unique_ptr
boost::weak_ptr -> std::weak_ptr
Pretty much the same
Few new features in std pointers

24. Lambdas
“Inline functions”
[capture](parameters)->return-type {body}
Very nice for iteration over data structures

25. Lambdas
std::vector<int> v;
v.push_back(1);
v.push_back(2);
v.push_back(3);
std::for_each(std::begin(v), std::end(v), [](int n){std::cout << n << std::endl;});
auto isOdd = [](int n) {return n%2==1;};
auto pos = std::find_if(std::begin(v), std::end(v), isOdd);
if(pos != std::end(v))
{
std::cout << *pos << std::endl;
}

26. static_assert
Compile time checks
static_assert((GREEKPI > 3.14) && (GREEKPI < 3.15), "GREEKPI is inaccurate!");
template<class T>
struct Check {
static_assert(sizeof(int) <= sizeof(T), "T is not big enough!");
};
template<class Integral>
Integral foo(Integral x, Integral y) {
static_assert(std::is_integral<Integral>::value, "foo() parameter must be an integral type.");
}

27. Uniform Initialization Syntax
C++
std::string s("hello");
int m=int(); //default initialization
int arr[4]={0,1,2,3};
struct tm today={0};
struct S {
int x;
int a[4];
S(): x(-1) {
a[0] = 1;
a[1] = 2;
a[2] = 4;
a[3] = 8;
}
};
C++11
std::string s{"hello"};
int m{}; //default initialization
int arr[4]={0,1,2,3};
struct tm today={0};
struct S {
int x;
int a[4];
S(): x{-1}, a{1, 2, 4, 8}
{}
};

28. Uniform Initialization Syntax
C++
std::vector<int> vec;
vec.push_back(1);
vec.push_back(2);
vec.push_back(3);
std::map<std::string, int> intMap;
intMap["a"] = 1;
intMap["b"] = 2;
intMap["c"] = 3;
int* a = new int[3];
a[0] = 1;
a[1] = 2;
a[2] = 0;
C++11
std::vector<int> vec{1, 2, 3};
std::map<std::string, int> intMap{ {"a", 1}, {"b", 2},
{"c", 3} };
int* a = new int[3] { 1, 2, 0 };

29. Constructors
C++
class SomeType {
int number;
private:
void Construct(int new_number) { number = new_number; }
public:
SomeType(int new_number) { Construct(new_number); }
SomeType() { Construct(42); }
};
// Note: Default argument not nice
C++11
class SomeType {
int number;
public:
SomeType(int new_number) : number(new_number) {}
SomeType() : SomeType(42) {}
};

30. Constructors
C++
class Foo {
public:
Foo() : abc(0), x(0), y(0), initialized(false) {};
Foo(int value) : abc(0), x(0), y(0), initialized(false) {};
private:
int *abc;
int x;
int y;
bool initialized;
};
C++11
class Foo {
public:
Foo() {};
Foo(int value) {};
private:
int *abc = 0;
int x = 0;
int y = 0;
bool initialized = false;
};

31. Constructors
C++
class BaseClass {
public:
BaseClass() {};
BaseClass(int value) {};
};
class DerivedClass : public BaseClass {
public:
DerivedClass() : BaseClass() {}
DerivedClass(int value) : BaseClass(value) {}
};
C++11
class BaseClass {
public:
BaseClass() {};
BaseClass(int value) {};
};
class DerivedClass : public BaseClass {
public:
using BaseClass::BaseClass;
};

32. Default and Delete
C++
struct NoCopy
{
private:
NoCopy & operator =( const NoCopy & ) {};
NoCopy ( const NoCopy & ) {};
};
struct A
{
A() {}
virtual ~A() {};
};
C++11
struct NoCopy
{
NoCopy & operator =( const NoCopy & ) = delete;
NoCopy ( const NoCopy & ) = delete;
};
struct A
{
A()=default;
virtual ~A()=default;
};

33. Tuple
typedef std::tuple <int, double, long &, const char *> test_tuple;
long lengthy = 12;
test_tuple proof (18, 6.5, lengthy, "Ciao!");
lengthy = std::get<0>(proof); // Assign to 'lengthy' the value 18.
std::get<3>(proof) = " Beautiful!"; // Modify the tuple’s fourth element.

34. Threads
std::mutex
std::condition_variable
std::lock_guard
std::thread
std::async, std::future

35. A lot more
move semantics
regular expressions
new algorithms
constexpr
extern/alias templates
alternative function syntax
new string literals
...

36. Further Info
http://en.wikipedia.org/wiki/C%2B%2B11
http://blog.smartbear.com/c-plus-plus/the-biggest-changes-in-c11-and-why-
you-should-care/
http://www.codeproject.com/Articles/570638/Ten-Cplusplus-Features-Every-
Cplusplus-Developer#movesemantics
http://www.cprogramming.com/c++11/rvalue-references-and-move-semantics-
in-c++11.html