gcc与字符串类型不一致 [英] gcc inconsistent about string type

问题描述

我有以下测试程序：

#include <string>
#include <iostream>

int main()
{
    std::string s;
    std::string a = "sd";

    std::cout << a==s ? "y" : "n";

    return 0;
}

尝试使用 g ++ test.cpp 给出以下隐含错误：

Trying to compile this with g++ test.cpp gives the following cryptic error:

error: no match for 'operator==' (operand types are 'std::basic_ostream<char>' and 'std::string {aka std::basic_string<char>}')
  std::cout << a==s ? "y" : "n";
                ^

看起来 s 正在正确编译为 std :: string ，而 a 正在编译为 std :: basic_ostream< char> !?帮助!!

It seems that s is being correctly compiled as type std::string, while a is being compiled as std::basic_ostream<char>!? HELP!!

推荐答案

编译器将您的语句解析为（（std :: cout< a）== s）？ y：n; 因为运算符优先< a>：您需要括号。

The compiler parsed your statement as ((std::cout << a) == s) ? "y" : "n"; because of operators precedence : You need parentheses.

std::cout << (a==s ? "y" : "n");

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