op_less.md

operator<

• string[meta header]
• std[meta namespace]
• function template[meta id-type]

namespace std {
  template <class CharT, class Traits, class Allocator>
  bool operator<(const basic_string<CharT, Traits, Allocator>& a,
                 const basic_string<CharT, Traits, Allocator>& b); // (1) C++03

  template <class CharT, class Traits, class Allocator>
  bool operator<(const basic_string<CharT, Traits, Allocator>& a,
                 const basic_string<CharT, Traits, Allocator>& b) noexcept; // (1) C++14

  template <class CharT, class Traits, class Allocator>
  bool operator<(const CharT* a,
                 const basic_string<CharT, Traits, Allocator>& b);          // (2)

  template <class CharT, class Traits, class Allocator>
  bool operator<(const basic_string<CharT, Traits, Allocator>& a,
                 const CharT* rhs) noexcept;                                // (3)
}

概要

basic_stringにおいて、左辺が右辺より小さいかの判定を行う。

戻り値

• (1) a.compare(b) < 0
• (2) b.compare(a) > 0
• (3) a.compare(b) < 0

例

#include <iostream>
#include <string>

int main()
{
  std::string a = "aaa";
  std::string b = "bbb";

  std::cout << std::boolalpha;
  std::cout << (a < b) << std::endl;
}

出力

true

参照

• LWG2064 - More noexcept issues in basic_string