gV0拜客生活常识网

20. 1 ModulesgV0拜客生活常识网

export and importgV0拜客生活常识网

20. 2 ConceptsgV0拜客生活常识网

template type requiresgV0拜客生活常识网

20. 3 Lambda TemplatesgV0拜客生活常识网

[]<>(){}gV0拜客生活常识网

20. 4 [likely] and [unlikely] AttributesgV0拜客生活常识网

if (choice) [[likely]]gV0拜客生活常识网

20. 5 RangesgV0拜客生活常识网

ranges::sort(vec);gV0拜客生活常识网

20. 6 CoroutinesgV0拜客生活常识网

co_awaitgV0拜客生活常识网

20. 7 std: : spangV0拜客生活常识网

span is = vec;gV0拜客生活常识网

20. 8 Mathematical ConstantsgV0拜客生活常识网

numbers::log2egV0拜客生活常识网

1 C++11

C++11 is an ISO C++ standard, published in 2011. To compile for this standard, add the -std=c++11 flag to a command-line compilation string if compiling with g++ or clang. If using Visual Studio, choose Project / Options / Configuration Properties / C/C++ / Language / C++ Language Standard and choose C++11. New Visual Studio versions already support this standard out of the box.gV0拜客生活常识网

11.1 Automatic Type Deduction

This standard introduces the auto keyword which deduces the type of the variable based on the variable’s initializer:gV0拜客生活常识网

int main()
{
    auto mychar = 'A';
    auto myint = 123 + 456;
    auto mydouble = 456.789;
}

11.2 Range-based Loops

The range-based loops allow us to iterate over the range, such as C++ standard-library containers:gV0拜客生活常识网

#include 
#include 
int main()
{
    std::vector v = { 10, 20, 40, 5, -20, 75 };
    for (auto el : v)
    {
        std::cout << el << '
';
    }
}

The range-based for loop is of the following form: for (type element : container). This is read as for each element in a container (do something).gV0拜客生活常识网

11.3 Initializer Lists

Initializer lists, represented by braces { } allow us to initialize objects in a uniform way. We can initialize single objects:gV0拜客生活常识网

int main()
{
    int x{ 123 };
    int y = { 456 };
    double d{ 3.14 };
}

And containers:gV0拜客生活常识网

#include 
int main()
{
    std::vector v = { 1, 2, 3, 4, 5 };
}

List initialization also prevents narrowing conversions. If we tried to initialize our integer object with a double value inside the initializer list, the compilation would fail:gV0拜客生活常识网

int main()
{
    int x = { 123.45 }; // Error, does not allowing narrowing
}

When initializing our objects, we should prefer initializer lists {} to old-style parentheses ().gV0拜客生活常识网

11.4 Move Semantics

C++ 11 standard introduces the move semantics for classes. We can initialize our objects by moving the data from other objects. This is achieved through move constructors and move assignment operators. Both accept the so-called rvalue reference as an argument. Lvalue is an expression that can be used on the left-hand side of the assignment operation. rvalues are expressions that can be used on the right-hand side of an assignment. The rvalue reference has the signature of some_type&&. To cast an expression to an rvalue reference, we use the std::move function. A simple move constructor and move assignment signature are:gV0拜客生活常识网

class MyClass
{
public:
    MyClass(MyClass&& otherobject) // move constructor
    {
        //implement the move logic here
    }
    MyClass& operator=(MyClass&& otherobject) // move assignment operator
    {
        // implement the copy logic here
        return *this;
    }
};