为什么我需要左值作为赋值的左操作数？ [关闭]

Question

简单的石头、剪刀、纸程序。
我收到错误消息：[Error] lvalue required as left operand of assignment. 我不知道出了什么问题，因为我是 C++ 编程新手，为什么它不接受 if 语句？

// Globale variabler
int PC, User; // For å sammenligne input
int Uavgjort = 0;
int user_score = 0;
int pc_score = 0;

int RandRange( int low, int high );
void Compare_values();



int main()
{
    srand( time( NULL ) );

    cout << "Valg:" << '\n';
    cout << "1. Stein" << '\n'
         << "2. Saks" << '\n'
         << "3. Papir" << '\n' << endl;

    while ( cin >> User )
    {
        RandRange( 1, 3 );
        Compare_values(); // sammenligner brukers verdi og random verdi
        if ( user_score >= 10 || pc_score >= 10 )
            break;
    } // while slutter her

    cout << "Game over!" << "\n\n";
    cout << "Score: \n" 
         << "PC Wins: " << pc_score << " times" << '\n'
         << "You won: " << user_score << " times" << '\n' << endl;

    cin.get();
}

int RandRange( int low, int high )
{
    PC = rand() % ( high - low + 1 ) + low;

    return PC;
}

void Compare_values()
{
        if ( User == 1 && PC == 1 )
        {
            cout << "Stein vs. Stein" << '\n';
            cout << "Uavgjort!" << '\n';
            ++Uavgjort;
        }
        else if ( User == 1 && PC == 2 )
        {
            cout << "Stein vs. Saks" << '\n';
            cout << "Du vant!" << '\n';
            ++user_score;
        }
        else if ( User == 1 && PC == 3 )
        {
            cout << "Stein vs. Papir" << '\n';
            cout << "Dessverre, du tapte." << '\n';
            ++pc_score;
        }
        else if ( User == 2 && PC = 1 )
        {
            cout << "Saks vs. Stein" << '\n';
            cout << "Dessverre, du tapte." << '\n';
            ++pc_score;
        }
        else if ( User == 2 && PC == 2 )
        {
            cout << "Saks vs. Saks" << '\n';
            cout << "Uavgjort!" << '\n';
            ++Uavgjort;
        }
        else if ( User == 2 && PC == 3 )
        {
            cout << "Saks vs. Papir" << '\n';
            cout << "Du vant!" << '\n';
            ++user_score;
        }
        else if ( User == 3 && PC == 1 )
        {
            cout << "Papir vs. Stein" << '\n';
            cout << "Du vant!" << '\n';
            ++user_score;
        }
        else if ( User == 3 && PC == 2 )
        {
            cout << "Papir vs. Saks" << '\n';
            cout << "Dessverre, du tapte." << '\n';
            ++pc_score;
        }
        else if ( User == 3 && PC == 3 )
        {
            cout << "Papir vs. Papir" << '\n';
            cout << "Uavgjort!" << '\n';
            ++Uavgjort;
        }
        else 
        {
            cout << "Jeg tror du har tastet feil verdi.." << '\n';
        }       
}           

Answer 1

你的错误在这一行

else if ( User == 2 && PC = 1 )

你可能是说

else if ( User == 2 && PC == 1 )
                       // ^^ 

否则，由于运算符优先级（其中 expression 不是适当的 lvalue），您会尝试将 1 分配给表达式 (User == 2 && PC)。 p>

请仔细阅读编译器错误消息，并检查它们告诉出现的行！