New in C++11

Trần Duy Quang – May 2014

Agenda

1. Automatic variables

2. Decltype

3. Rvalue reference

4. Lambda function

5. Variadic template

6. Concurrency library

2

Compiler support

3

VS 2010

Automatic variables

Decltype

Rvalue reference

Lambda function

VS 2012

Concurrency library

Memory model

VS 2013

Variadic template

Custom literal

Delegating constructor

VS 13: Some C++14 features!

auto Variables

Implicit variable declaration

Keyword: auto

4Note: cbegin to iterate constant, no change in content

Careful: auto default

By-value for references

Use auto& or decltype for desired result!

5

int f, not int& f!

More mindblow

int&: auto is int (only, no &)

But int*: auto is int* !

6

std::bind

Placeholder objects _1, _2, .., _N

C# alike

7

1. May cause runtime error, but when?

2. What about _10 rather than _2?

Range-based for loop

8

Better? auto&!

decltype

Query the type of an expression

Primary use in generic programming1

91Algorithms are written in terms of to-be-specified-later types that are then instantiated when needed for specific types provided as parameters

Why do we have to use auto & decltype here?

auto without decltype

Compile error

10

Why auto & decltype?

11

Parenthesized variable

Always a reference!

12

decltype vs auto

decltype of a variable

returns the type of that variable, including top-level

const and references

decltype depends on its form of variable

Parenthesis always yield a reference

13

C++ Primer 2014:

What do we have?

14

Type of xType of y

Why?decltype(x) y auto y = x

const int const int int Strips top-level cv-qualifiers

int[100] int[100] int* Performs array to pointer conversion

int f (int) int f (int) int (*) (int) Performs function to function pointer conversion

int& int& int Auto remove references

int&& int&& int

Don’t forget the reference with parenthesis from decltype! decltype( (x) )

auto vs decltype conclustion

auto

Everyday use

Assign the value of some expression to a new variable

decltype

Template & generic programming (library code)

a new variable with precisely the same type

15

More mindblow (again)

decltype(auto) f = expression; // C++14

C++17 will go further? No ideas!

16

Lambda function

17

Lambda function

[]: capture list

[] () -> return type

18

Lambda capture

Capture by value

42

Capture by reference

43

43

(Can be modify inside, but not affect outside)

19

Types of capture

[=]: automatic capture all by value

[&]: automatic capture all by reference

[this]: capture this pointer by value

[a, &b]: capture a by value and b by reference

20

Recursive lambda

21

Stateless lambda

Convertible to function pointer!

Used with C-style API (e.g. Win32)

22

High-order function

Takes one or more functions as an input

Outputs a function

23

Sắp xếp tăng dần

Generic lambda

Take a deep breath! (C++14 only)

We can write

auto auto (auto auto) { auto; };

Compiler infers the rest from the context

Actually, this is NOT a type deduction

This is a template!

24

Let’s see one generic lambda

25Did I tell you about functor?

Lambda physiology

For each lambda compiler generate a class

Specifying lambda instantiate an object

Invoking lambda call the object’s operator()

26

Rvalue reference

27

Rvalue definition

lvalue: can appear on the left and right

rvalue: can only appear on the right

28

Move semantics

What do we need from the last line?

Destruct the resource held by hello first

Clone resource from temp returned

Destruct temp & release its resources

29

More efficient?

Swap resources pointers

Let temp destructor destruct hello’s original resources

Obvious solution

Overload operator= ! (Copy assignment)

Right hand side should be passed by reference

rvalue references!

MyString&&: rvalue reference to MyString&

30

Function overload resolution

“Am I being called on an lvalue or rvalue?”

31

Achieving move semantics

Should occur only for copy constructor and

assignment operator!

32

Forcing move semantics

std::move help

Type with no move semantics implementation?

Swap like old times!

33

Funny jokes

34

Smart pointers

35

Three types of smart pointer

unique_ptr<T> - Single ownership

Deleted when pointer dies

shared_ptr<T> - Shared ownership

Reference pointer counting

weak_ptr<T> - Cycle breaking

auto_ptr deprecated!

36

Before we go on

Resource Acquisition Is Initialization (RAII)

37

RAII in C++ has been around for over a decade

C++11 encourages its use as default

Smart pointers help building RAII around legacy

interfaces

Move semantics makes passing resources around

cheap

38

unique_ptr

39

shared_ptr

Last pointer dies, object is deleted

40

weak_ptr

Does not affect reference count

Break cycles between shared_ptrs

41

Some other things

42

Threads & Async

43

Variadic template

44

Rules of expansion

45

Initializer list

46

using

47

Raw string literals

48

Other examples of raw string literals

49

Tuple

50

Default & delete

51

The last coffee drop

52

C++ Accelerated Massive

Parallelism

53

Simple example

54

Normal version AMP version

Basic elements of AMP

55

Code run on each thread

Thread id running the

lambda

Check if code can run with AMP / Direct3D

Reference 1

Slide C++11

Slide What’s new in C++11

Slide The future of C++

Slide The style of C++11

Slide C++11

Slide C++11 idioms

Slide What’s new in Visual C++11

Slide C++11 – Feel the new language

Slide C++11 Talk

56

Reference 2

Slide C++11 – A change in style

Slide New C++ Standard – C++11

Slide Advanced C++ runtime improvement

techniques

Slide Hot C+11 Rvalue references and Move

semantics

Slide C++ usage experience

57

Reference 3

Ebook C++11 for programmers 2014

Ebook C++ Primer 5th Edition 2013

Ebook C Primer Plus 2014

Ebook Effective C++ 3rd Ed 55 Specific Ways to

Improve Your Programs and Designs 2005

Ebook Effective C++ & More effective C++

58