initializer_list Class

  • Artigo

 

The latest version of this topic can be found at initializer_list Class.

Provides access to an array of elements in which each member is of the specified type.

Syntax

template <class Type>  
class initializer_list

Parameters

Parameter Description
_Elem The element data type to be stored in the initializer_list.
first The pointer to the first element of the initializer_list.
last The pointer to the last element of the initializer_list.

Remarks

An initializer_list can be constructed using a braced initializer list:

initializer_list<int> i1{ 1, 2, 3, 4 };

The compiler transforms braced initializer lists with homogeneous elements into an initializer_list whenever the function signature requires an initializer_list. For more details on using initializer_list, see Uniform Initialization and Delegating Constructors

Constructors

initializer_list Constructs an object of type initializer_list.

Typedefs

value_type The type of the elements in the initializer_list.
reference A type that provides a reference to an element in the initializer_list.
const_reference A type that provides a constant reference to an element in the initializer_list.
size_type A type that represents the number of elements in the initializer_list.
iterator A type that provides an iterator for the initializer_list.
const_iterator A type that provides a constant iterator for the initializer_list.

Member Functions

begin Returns a pointer to the first element in an initializer_list.
end Returns a pointer to one past the last element in an initializer_list.
size Returns the number of elements in the initializer_list.

Requirements

Header: <initializer_list>

Namespace: std

initializer_list::begin

Returns a pointer to the first element in an initializer_list.

constexpr const InputIterator* begin() const noexcept;

Return Value

A pointer to the first element of the initializer_list. If the list is empty, the pointer is the same for the beginning and end of the list.

Remarks

initializer_list::end

Returns a pointer to one past the last element in an initializer list.

constexpr const InputIterator* end() const noexcept;

Return Value

A pointer to one past the last element in the list. If the list is empty, this is the same as the pointer to the first element in the list.

initializer_list::initializer_list

Constructs an object of type initializer_list.

constexpr initializer_list() noexcept;initializer_list(const InputIterator First, const InputIterator Last);

Parameters

Parameter Description
First The position of the first element in the range of elements to be copied.
Last The position of the first element beyond the range of elements to be copied.

Remarks

An initializer_list is based on an array of objects of the specified type. Copying an initializer_list creates a second instance of a list pointing to the same objects; the underlying objects are not copied.

Example

// initializer_list_class.cpp  
// compile with: /EHsc  
#include <initializer_list>  
#include <iostream>  
  
int main()  
{  
    using namespace std;  
    // Create an empty initializer_list c0  
    initializer_list <int> c0;  
  
    // Create an initializer_list c1 with 1 element  
    initializer_list <int> c1{ 3 };  
  
    // Create an initializer_list c2 with 5 elements   
    initializer_list <int> c2{ 5, 4, 3, 2, 1 };  
  
    // Create a copy, initializer_list c3, of initializer_list c2  
    initializer_list <int> c3(c2);  
  
    // Create a initializer_list c4 by copying the range c3[ first,  last)  
    const int* c3_ptr = c3.begin();  
    c3_ptr++;  
    c3_ptr++;  
    initializer_list <int> c4(c3.begin(), c3_ptr);  
  
    // Move initializer_list c4 to initializer_list c5  
    initializer_list <int> c5(move(c4));  
  
    cout << "c1 =";  
    for (auto c : c1)  
        cout << " " << c;  
    cout << endl;  
  
    cout << "c2 =";  
    for (auto c : c2)  
        cout << " " << c;  
    cout << endl;  
  
    cout << "c3 =";  
    for (auto c : c3)  
        cout << " " << c;  
    cout << endl;  
  
    cout << "c4 =";  
    for (auto c : c4)  
        cout << " " << c;  
    cout << endl;  
  
    cout << "c5 =";  
    for (auto c : c5)  
        cout << " " << c;  
    cout << endl;  
}  

c1 = 3c2 = 5 4 3 2 1c3 = 5 4 3 2 1c4 = 5 4c5 = 5 4

initializer_list::size

Returns the number of elements in the list.

constexpr size_t size() const noexcept;

Return Value

The number of elements in the list.

Remarks

See Also

<forward_list>