用C语言写有理数的四则运算

### 回答1：
可以使用结构体来表示有理数，结构体包含分子和分母两个整数成员。四则运算可以通过分别对分子和分母进行加、减、乘、除的操作来实现。具体实现可以参考以下代码：

#include <stdio.h>

typedef struct {
    int numerator;  // 分子
    int denominator;  // 分母
} Rational;

// 求最大公约数
int gcd(int a, int b) {
    return b ==  ? a : gcd(b, a % b);
}

// 化简有理数
void simplify(Rational *r) {
    int g = gcd(r->numerator, r->denominator);
    r->numerator /= g;
    r->denominator /= g;
}

// 加法
Rational add(Rational r1, Rational r2) {
    Rational result;
    result.numerator = r1.numerator * r2.denominator + r2.numerator * r1.denominator;
    result.denominator = r1.denominator * r2.denominator;
    simplify(&result);
    return result;
}

// 减法
Rational subtract(Rational r1, Rational r2) {
    Rational result;
    result.numerator = r1.numerator * r2.denominator - r2.numerator * r1.denominator;
    result.denominator = r1.denominator * r2.denominator;
    simplify(&result);
    return result;
}

// 乘法
Rational multiply(Rational r1, Rational r2) {
    Rational result;
    result.numerator = r1.numerator * r2.numerator;
    result.denominator = r1.denominator * r2.denominator;
    simplify(&result);
    return result;
}

// 除法
Rational divide(Rational r1, Rational r2) {
    Rational result;
    result.numerator = r1.numerator * r2.denominator;
    result.denominator = r1.denominator * r2.numerator;
    simplify(&result);
    return result;
}

int main() {
    Rational r1 = {2, 3};
    Rational r2 = {3, 4};
    Rational r3 = add(r1, r2);
    printf("%d/%d + %d/%d = %d/%d\n", r1.numerator, r1.denominator, r2.numerator, r2.denominator, r3.numerator, r3.denominator);
    Rational r4 = subtract(r1, r2);
    printf("%d/%d - %d/%d = %d/%d\n", r1.numerator, r1.denominator, r2.numerator, r2.denominator, r4.numerator, r4.denominator);
    Rational r5 = multiply(r1, r2);
    printf("%d/%d * %d/%d = %d/%d\n", r1.numerator, r1.denominator, r2.numerator, r2.denominator, r5.numerator, r5.denominator);
    Rational r6 = divide(r1, r2);
    printf("%d/%d / %d/%d = %d/%d\n", r1.numerator, r1.denominator, r2.numerator, r2.denominator, r6.numerator, r6.denominator);
    return ;
}

### 回答2：
在C语言中，可以使用结构体来表示有理数，结构体包含两个整数成员numerator（分子）和denominator（分母）。

接下来，我们可以定义一些函数来实现有理数的四则运算：

1. 加法（addition）函数：

struct Rational add(struct Rational r1, struct Rational r2) {
    struct Rational result;
    result.numerator = r1.numerator * r2.denominator + r2.numerator * r1.denominator;
    result.denominator = r1.denominator * r2.denominator;
    return result;
}

2. 减法（subtraction）函数：

struct Rational subtract(struct Rational r1, struct Rational r2) {
    struct Rational result;
    result.numerator = r1.numerator * r2.denominator - r2.numerator * r1.denominator;
    result.denominator = r1.denominator * r2.denominator;
    return result;
}

3. 乘法（multiplication）函数：

struct Rational multiply(struct Rational r1, struct Rational r2) {
    struct Rational result;
    result.numerator = r1.numerator * r2.numerator;
    result.denominator = r1.denominator * r2.denominator;
    return result;
}

4. 除法（division）函数：

struct Rational divide(struct Rational r1, struct Rational r2) {
    struct Rational result;
    result.numerator = r1.numerator * r2.denominator;
    result.denominator = r1.denominator * r2.numerator;
    return result;
}

上述函数中，我们利用了分子和分母的性质，通过运算得到了结果的分子和分母，最后构造并返回了一个新的有理数结构体。

需要注意的是，使用这些函数之前需要先定义一个有理数的结构体类型struct Rational，并根据具体情况进行初始化。由于最后的结果可能需要进行约分，我们可以再编写一个约分（reduction）函数对结果进行化简。

### 回答3：
C语言可以通过定义结构体来实现有理数的四则运算。

首先，我们可以定义一个有理数的结构体，包含两个整数成员分子和分母：

typedef struct {
    int numerator;   // 分子
    int denominator; // 分母
} Rational;

接下来，可以实现有理数的加法、减法、乘法和除法运算函数：

Rational add(Rational num1, Rational num2) {
    Rational result;
    result.numerator = num1.numerator * num2.denominator + num2.numerator * num1.denominator;
    result.denominator = num1.denominator * num2.denominator;
    return result;
}

Rational subtract(Rational num1, Rational num2) {
    Rational result;
    result.numerator = num1.numerator * num2.denominator - num2.numerator * num1.denominator;
    result.denominator = num1.denominator * num2.denominator;
    return result;
}

Rational multiply(Rational num1, Rational num2) {
    Rational result;
    result.numerator = num1.numerator * num2.numerator;
    result.denominator = num1.denominator * num2.denominator;
    return result;
}

Rational divide(Rational num1, Rational num2) {
    Rational result;
    result.numerator = num1.numerator * num2.denominator;
    result.denominator = num1.denominator * num2.numerator;
    return result;
}

使用上述定义和函数，可以进行两个有理数的四则运算：

Rational num1 = {1, 2}; // 1/2
Rational num2 = {3, 4}; // 3/4

Rational sum = add(num1, num2); // 相加
Rational difference = subtract(num1, num2); // 相减
Rational product = multiply(num1, num2); // 相乘
Rational quotient = divide(num1, num2); // 相除

以上就是用C语言实现有理数的四则运算的简单示例，希望能对你有所帮助。