比较 std::string 和 C 风格的字符串文字

Question

假设我有以下代码：

#include <iostream>
#include <string>
#include <iomanip>
using namespace std; // or std::

int main()
{
    string s1{ "Apple" };
    cout << boolalpha;
    cout << (s1 == "Apple") << endl; //true
}

我的问题是：系统如何检查这两者？ s1 是一个对象，而 "Apple" 是一个 C 风格的字符串 文字。

据我所知，不同的数据类型是不能比较的。我在这里错过了什么？

Answer 1

是因为下面的compare operator defined for std::string

template< class CharT, class Traits, class Alloc >
bool operator==( const basic_string<CharT,Traits,Alloc>& lhs, const CharT* rhs );  // Overload (7)

这允许在 std::string 和 const char* 之间进行比较。这就是魔法！

窃取 @Pete Becker 的评论：

"For completeness, if this overload did not exist, the comparison would still work; The compiler would construct a temporary object of type std::string from the C-style string and compare the two std::string objects, using the first overload of operator==
template< class CharT, class Traits, class Alloc >
bool operator==( const basic_string<CharT,Traits,Alloc>& lhs,
                 const basic_string<CharT,Traits,Alloc>& rhs );   // Overload (1)
Which is why this operator(i.e. overload 7) is there: it eliminates the need for that temporary object and the overhead involved in creating and destroying it."

比较 std::string 和 C 风格的字符串文字

Comparing std::string and C-style string literals

c++

comparison

c-strings

stdstring

c++-standard-library