std::basic_string<CharT,Traits,Allocator>::size, (3) - Linux Manuals

std::basic_string<CharT,Traits,Allocator>::size,: std::basic_string<CharT,Traits,Allocator>::size,

NAME

std::basic_string<CharT,Traits,Allocator>::size, - std::basic_string<CharT,Traits,Allocator>::size,

Synopsis

size_type size() const;             (until C++11)
size_type size() const noexcept;    (since C++11)
size_type length() const;           (until C++11)
size_type length() const noexcept;  (since C++11)

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

// Run this code

 #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(u8"ハロー・ワールド"); // 8 code points
  assert(24 == c.size()); // 24 code units in UTF-8
 }