c++ - 在 if 语句中比较结构内的值

Question

我正在用 C++ 编写分数简化器。我正在尝试比较结构中的两个值以查看哪个更大，以下均不起作用：

void simplify(struct Fraction* fraction) {
    if (fraction->numerator) > (fraction->denominator)
    {
        cout << "test";
    }
}

void simplify(struct Fraction* fraction) {
    if (fraction.numerator) > (fraction.denominator)
    {
        cout << "test";
    }
}

结构：

struct Fraction {
    int numerator;
    int denominator;
};

错误：

w2.cpp: In function void simplify(Fraction*):
w2.cpp:40:15: error: request for member numerator in fraction, which is of non-class type Fraction*
w2.cpp:40:26: error: expected primary-expression before > token
w2.cpp:40:38: error: request for member denominator in fraction, which is of non-class type Fraction*
w2.cpp:41:2: error: expected ; before { token

如何比较结构内的值？

Answer 1

你有指针，所以你需要取消引用它们。你也有括号问题：

void simplify(struct Fraction* fraction) {
    if (fraction->numerator > fraction->denominator)
    {
        cout << "test";
    }
}

您可以通过传递引用来避免所有这些指针取消引用的麻烦。另外，删除不必要struct的 s：

void simplify(const Fraction& fraction) {
    if (fraction.numerator > fraction.denominator) {
        cout << "test";
    }
}

Answer 2

您只是缺少一对括号：

void simplify(struct Fraction* fraction) {
    if ( (fraction->numerator) > (fraction->denominator) )
    {
        cout << "test";
    }
}