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- 字符串库
- std::basic_string
- std::basic_string<CharT,Traits,Allocator>::npos
- std::basic_string<CharT,Traits,Allocator>::at
- std::hash (std::string, std::wstring, std::u16string, std::u32string, std::pmr::string, std::pmr::wstring, std::pmr::u16string, std::pmr::u32string)
- std::basic_string<CharT,Traits,Allocator>::assign
- std::basic_string<CharT,Traits,Allocator>::get_allocator
- std::basic_string<CharT,Traits,Allocator>::substr
- std::basic_string<CharT,Traits,Allocator>::basic_string
- std::basic_string<CharT,Traits,Allocator>::operator=
- std::basic_string<CharT,Traits,Allocator>::operator[]
- std::basic_string<CharT,Traits,Allocator>::front
- std::basic_string<CharT,Traits,Allocator>::back
- std::basic_string<CharT,Traits,Allocator>::data
- std::basic_string<CharT,Traits,Allocator>::c_str
- std::basic_string<CharT,Traits,Allocator>::operator basic_string_view
- std::basic_string<CharT,Traits,Allocator>::begin, std::basic_string<CharT,Traits,Allocator>::cbegin
- std::basic_string<CharT,Traits,Allocator>::end, std::basic_string<CharT,Traits,Allocator>::cend
- std::basic_string<CharT,Traits,Allocator>::rbegin, std::basic_string<CharT,Traits,Allocator>::crbegin
- std::basic_string<CharT,Traits,Allocator>::rend, std::basic_string<CharT,Traits,Allocator>::crend
- std::basic_string<CharT,Traits,Allocator>::empty
- std::basic_string<CharT,Traits,Allocator>::size, std::basic_string<CharT,Traits,Allocator>::length
- std::basic_string<CharT,Traits,Allocator>::max_size
- std::basic_string<CharT,Traits,Allocator>::reserve
- std::basic_string<CharT,Traits,Allocator>::capacity
- std::basic_string<CharT,Traits,Allocator>::shrink_to_fit
- std::basic_string<CharT,Traits,Allocator>::clear
- std::basic_string<CharT,Traits,Allocator>::insert
- std::basic_string<CharT,Traits,Allocator>::erase
- std::basic_string<CharT,Traits,Allocator>::push_back
- std::basic_string<CharT,Traits,Allocator>::pop_back
- std::basic_string<CharT,Traits,Allocator>::append
- std::basic_string<CharT,Traits,Allocator>::operator+=
- std::basic_string<CharT,Traits,Allocator>::compare
- std::basic_string<CharT,Traits,Allocator>::starts_with
- std::basic_string<CharT,Traits,Allocator>::ends_with
- std::basic_string<CharT,Traits,Allocator>::replace
- std::basic_string<CharT,Traits,Allocator>::copy
- std::basic_string<CharT,Traits,Allocator>::resize
- std::basic_string<CharT,Traits,Allocator>::swap
- std::basic_string<CharT,Traits,Allocator>::find
- std::basic_string<CharT,Traits,Allocator>::rfind
- std::basic_string<CharT,Traits,Allocator>::find_first_of
- std::basic_string<CharT,Traits,Allocator>::find_first_not_of
- std::basic_string<CharT,Traits,Allocator>::find_last_of
- std::basic_string<CharT,Traits,Allocator>::find_last_not_of
- std::operator+(std::basic_string)
- std::swap(std::basic_string)
- std::literals::string_literals::operator""s
- std::erase, std::erase_if (std::basic_string)
- operator<<,>>(std::basic_string)
- std::getline
- operator==,!=,<,<=,>,>=,<=>(std::basic_string)
- std::stoi, std::stol, std::stoll
- std::stoul, std::stoull
- std::stof, std::stod, std::stold
- std::to_string
- std::to_wstring
- std::basic_string 的推导指引
- std::basic_string_view
- 空终止字节字符串
- 空终止多字节字符串
- 空终止宽字符串
- std::char_traits
- 注释
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- 实验性 C++ 特性
- 有用的资源
- 索引
- std 符号索引
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- C++ 关键词
位置：首页 > C++ 参考手册 >字符串库 >std::basic_string > std::basic_string<CharT,Traits,Allocator>::empty
std::basic_string<CharT,Traits,Allocator>::empty
| bool empty() const; |
(C++11 前) | |
| bool empty() const noexcept; |
(C++11 起) (C++20 前) |
|
| [[nodiscard]] constexpr bool empty() const noexcept; |
(C++20 起) | |
检查 string 是否无字符，即是否 begin() == end() 。
参数
（无）
返回值
若 string 为空则为 true ，否则为 false 。
复杂度
常数。
示例
运行此代码
#include <iostream> #include <string> int main() { std::string s; std::boolalpha(std::cout); std::cout << "s.empty():" << s.empty() << "\t s:'" << s << "'\n"; s = "Exemplar"; std::cout << "s.empty():" << s.empty() << "\t s:'" << s << "'\n"; s = ""; std::cout << "s.empty():" << s.empty() << "\t s:'" << s << "'\n"; }
输出：
s.empty():true s:'' s.empty():false s:'Exemplar' s.empty():true s:''
参阅
| 返回字符数 (公开成员函数) |