用c语言写一个简单的计算器 包括加减乘除和阶乘等运算 并且计算器中有菜单选项

在C语言中编写一个简单的命令行计算器，包括基本的四则运算以及阶乘功能，我们可以设计一个结构化的菜单驱动程序。下面是一个基础的示例：

#include <stdio.h>
#include <math.h>

// 定义计算函数
double add(double a, double b) {
    return a + b;
}
double subtract(double a, double b) {
    return a - b;
}
double multiply(double a, double b) {
    return a * b;
}
double divide(double a, double b) {
    if (b != 0)
        return a / b;
    else
        printf("Error: Division by zero is not allowed.\n");
    return 0;
}
double factorial(int n) {
    if (n == 0 || n == 1)
        return 1;
    else
        return n * factorial(n - 1);
}

// 主菜单函数
void menu() {
    int choice;
    printf("\nCalculator Menu:\n");
    printf("1. Addition\n");
    printf("2. Subtraction\n");
    printf("3. Multiplication\n");
    printf("4. Division\n");
    printf("5. Factorial\n");
    printf("6. Exit\n");
    scanf("%d", &choice);

    switch (choice) {
        case 1: // 加法
            double num1, num2;
            printf("Enter two numbers for addition: ");
            scanf("%lf %lf", &num1, &num2);
            printf("Result: %.2f\n", add(num1, num2));
            break;
        case 2: // 减法
            scanf("%lf %lf", &num1, &num2);
            printf("Result: %.2f\n", subtract(num1, num2));
            break;
        case 3: // 乘法
            scanf("%lf %lf", &num1, &num2);
            printf("Result: %.2f\n", multiply(num1, num2));
            break;
        case 4: // 除法
            scanf("%lf %lf", &num1, &num2);
            divide(num1, num2);
            break;
        case 5: // 阶乘
            int fact_num;
            printf("Enter an integer for factorial: ");
            scanf("%d", &fact_num);
            printf("Factorial: %d\n", factorial(fact_num));
            break;
        case 6: // 退出
            printf("Exiting calculator...\n");
            break;
        default:
            printf("Invalid choice. Please try again.\n");
            break;
    }
}

int main() {
    while (true) {
        menu();
    }
    return 0;
}