std:: data
From cppreference.com
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Defined in header
<array>
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Defined in header
<deque>
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Defined in header
<flat_map>
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Defined in header
<flat_set>
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Defined in header
<forward_list>
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Defined in header
<inplace_vector>
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Defined in header
<iterator>
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Defined in header
<list>
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Defined in header
<map>
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Defined in header
<regex>
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Defined in header
<set>
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Defined in header
<span>
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Defined in header
<string>
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Defined in header
<string_view>
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Defined in header
<unordered_map>
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Defined in header
<unordered_set>
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Defined in header
<vector>
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template
<
class
C
>
constexpr auto data ( C & c ) - > decltype ( c. data ( ) ) ; |
(1) | (since C++17) |
|
template
<
class
C
>
constexpr auto data ( const C & c ) - > decltype ( c. data ( ) ) ; |
(2) | (since C++17) |
|
template
<
class
T,
std::
size_t
N
>
constexpr T * data ( T ( & array ) [ N ] ) noexcept ; |
(3) | (since C++17) |
|
template
<
class
E
>
constexpr const E * data ( std:: initializer_list < E > il ) noexcept ; |
(4) | (since C++17) |
Returns a pointer to the block of memory containing the elements of the range.
1,2)
Returns
c.
data
(
)
.
3)
Returns
array
.
4)
Returns
il.
begin
(
)
.
Parameters
| c | - | a container or view with a data ( ) member function |
| array | - | an array of arbitrary type |
| il | - | an std::initializer_list |
Return value
1,2)
c.
data
(
)
3)
array
4)
il.
begin
(
)
Exceptions
1)
May throw implementation-defined exceptions.
Notes
The overload for
std::initializer_list
is necessary because it does not have a member function
data
.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_nonmember_container_access
|
201411L | (C++17) |
std::size()
,
std::data()
, and
std::empty()
|
Possible implementation
| First version |
|---|
template<class C> constexpr auto data(C& c) -> decltype(c.data()) { return c.data(); } |
| Second version |
template<class C> constexpr auto data(const C& c) -> decltype(c.data()) { return c.data(); } |
| Third version |
template<class T, std::size_t N> constexpr T* data(T (&array)[N]) noexcept { return array; } |
| Fourth version |
template<class E> constexpr const E* data(std::initializer_list<E> il) noexcept { return il.begin(); } |
Example
Run this code
#include <cstring> #include <iostream> #include <string> int main() { std::string s{"Hello world!\n"}; char a[20]; // storage for a C-style string std::strcpy(a, std::data(s)); // [s.data(), s.data() + s.size()] is guaranteed to be an NTBS since C++11 std::cout << a; }
Output:
Hello world!
See also
|
(C++20)
|
obtains a pointer to the beginning of a contiguous range
(customization point object) |
|
(C++20)
|
obtains a pointer to the beginning of a read-only contiguous range
(customization point object) |