用c语言完善简单科学计算器程序，要求尽可能利用所学过的分支判断结构语句，循环控制语句，函数和递归函数尽可能多的实现除了单项简单加减乘除之外的：复合四则运算，累加，累乘，平方，开方等运算。

在C语言中，我们可以创建一个完善的科学计算器程序，它不仅包含基本的加、减、乘、除运算，还包含了复合四则运算、累加、累乘、平方和开方等高级功能。这里是一个简单的示例：

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

// 单项运算函数
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; // 返回0避免悬空指针
}

// 复合运算函数（如：a*(b+c)）
double compound_operation(double a, double b, char op1, char op2) {
    double intermediate = 0;
    switch (op1) {
        case '+':
            intermediate = add(a, b);
            break;
        case '-':
            intermediate = subtract(a, b);
            break;
        default:
            printf("Invalid operation.\n");
            return 0;
    }
    switch (op2) {
        case '*':
            return multiply(intermediate, b);
        case '/':
            return divide(intermediate, b);
        case '^': // 幂运算
            return pow(intermediate, b); // 注意：实际项目需要处理负数开方
        default:
            printf("Invalid operation.\n");
            return 0;
    }
}

// 累加和累乘
double sum(int n, double arr[]) {
    double total = 0;
    for (int i = 0; i < n; i++) {
        total += arr[i];
    }
    return total;
}

double product(int n, double arr[]) {
    double result = 1;
    for (int i = 0; i < n; i++) {
        result *= arr[i];
    }
    return result;
}

// 平方和开方（使用数学库函数）
double square(double num) {
    return pow(num, 2);
}

double sqrt(double num) {
    if (num >= 0)
        return sqrt(num);
    else
        printf("Error: Square root of negative number is not defined.\n");
    return 0;
}

int main() {
    double a, b;
    char op1, op2;

    printf("Enter two numbers and an operator (+, -, *, /, ^): ");
    scanf("%lf %lf %c %c", &a, &b, &op1, &op2);

    // 根据用户输入调用相应的计算函数
    switch (op1) {
        case '+':
            printf("Result: %.2f\n", add(a, b));
            break;
        case '-':
            printf("Result: %.2f\n", subtract(a, b));
            break;
        case '*':
            printf("Result: %.2f\n", multiply(a, b));
            break;
        case '/':
            printf("Result: %.2f\n", divide(a, b));
            break;
        case '^':
            printf("Result: %.2f\n", compound_operation(a, b, op1, op2));
            break;
    }

    int n;
    printf("Enter the number of elements in array for sum or product: ");
    scanf("%d", &n);
    double arr[n];
    printf("Enter array elements: ");
    for (int i = 0; i < n; i++) {
        scanf("%lf", &arr[i]);
    }
    printf("Sum: %.2f, Product: %.2f\n", sum(n, arr), product(n, arr));

    printf("Square of %.2f: %.2f\n", b, square(b));
    printf("Square root of %.2f: %.2f\n", b, sqrt(b));

    return 0;
}