std::basic_string<CharT,Traits,Allocator>:: size, std::basic_string<CharT,Traits,Allocator>:: length
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
size_type size
(
)
const
;
|
(1) |
(noexcept since C++11)
(constexpr since C++20) |
|
size_type length
(
)
const
;
|
(2) |
(noexcept since C++11)
(constexpr since C++20) |
Returns the number of
CharT
elements in the string, i.e.
std::
distance
(
begin
(
)
, end
(
)
)
.
Parameters
(none)
Return value
The number of
CharT
elements in the string.
Complexity
|
Unspecified |
(until C++11) |
|
Constant |
(since C++11) |
Notes
For std::string , the elements are bytes (objects of type char ), which are not the same as characters if a multibyte encoding such as UTF-8 is used.
Example
#include <cassert> #include <iterator> #include <string> int main() { std::string s("Exemplar"); assert(8 == s.size()); assert(s.size() == s.length()); assert(s.size() == static_cast<std::string::size_type>( std::distance(s.begin(), s.end()))); std::u32string a(U"ハロー・ワールド"); // 8 code points assert(8 == a.size()); // 8 code units in UTF-32 std::u16string b(u"ハロー・ワールド"); // 8 code points assert(8 == b.size()); // 8 code units in UTF-16 std::string c("ハロー・ワールド"); // 8 code points assert(24 == c.size()); // 24 code units in UTF-8 #if __cpp_lib_char8_t >= 201907L std::u8string d(u8"ハロー・ワールド"); // 8 code points assert(24 == d.size()); // 24 code units in UTF-8 #endif }
See also
|
checks whether the string is empty
(public member function) |
|
|
returns the maximum number of characters
(public member function) |
|
|
returns the number of characters
(public member function of
std::basic_string_view<CharT,Traits>
)
|