如果总是返回真

2021-12-12 00:00:00 if-statement c++

我只是用 C++ 做一些实验，但我不明白为什么两个 if 语句都返回 true:

I'm just experimenting a bit with C++ but I can't figure out why both if-statements return true:

#include <iostream>
#include <windows.h>
using namespace std;

int main()
{
    cout << "Language?" << endl;
    string lang;
    cin >> lang;
    if(lang == "Deutsch" || "deutsch")
    {
        cout << "Hallo Welt!";
    }
    else
    {
        return false;
    }
    if(lang == "English" || "english")
    {
        cout << "Hello World!";
    }
    else
    {
        return false;
    }
    return 0;
}

我对 C++ 和 stackoverflow 还是很陌生，所以如果这是一个愚蠢的或经常被问到的问题，我很抱歉，但我真的不知道更多.请帮忙！

I'm pretty new to C++ and stackoverflow so I'm sorry if that's an stupid or frequently asked question but I really don't know any further. Please help!

推荐答案

 lang == "Deutsch" || "deutsch"

错了

lang == "Deutsch" || lang == "deutsch"

是对的

deutsch"单独返回内存中字符串的地址.这是永远不等于零.这意味着正确.

"deutsch" alone returns the address of the string in memory. which is always not equal to zero. which means true.

a == "hello" || "bob"

意思

(a == "hello") || "bob"

不管 a == "hello" 结果是什么(真或假)，false ||"bob" 变成 false ||指向bob"的指针.所有非空指针都是true，所以这是false ||true 即 true.

regardless of what a == "hello" results in (true or false), false || "bob" becomes false || pointer to "bob". All non-null pointers are true, so this is false || true which is true.

#include <iostream>
#include <windows.h>
using namespace std;

int main()
{
    cout << "Language?" << endl;
    string lang;
    cin >> lang;
    if(lang == "Deutsch" || lang == "deutsch")
    {
        cout << "Hallo Welt!";
    }
    else
    {
        return false;
    }
    if(lang == "English" || lang == "english")
    {
        cout << "Hello World!";
    }
    else
    {
        return false;
    }
    return 0;
}

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