c - 只是想知道我的代码 C 编程到底出了什么问题

Question

我不知道我的代码出了什么问题，我正在使用 Visual Studio，它说我没有标识符，我不能 100% 确定这意味着什么，我基本上必须为 pow 编写一个新函数，我不太明白太多了，但是如果有人可以看看我的代码，那将会非常有帮助，谢谢

// Programmer:     Your Name
// Date:           Date
// Program Name:   The name of the program
// Chapter:        Chapter # - Chapter name
// Description:    2 complete English sentences describing what the  program does,
//                 algorithm used, etc.
#define _CRT_SECURE_NO_WARNINGS // Disable warnings (and errors) when using non-secure versions of printf, scanf, strcpy, etc.
#include <stdio.h> // Needed for working with printf and scanf
#include <math.h>
#include <string.h>

int main(void)
{
    // Constant and Variable Declarations
    double power(double num, int power) {
        double result = 1;
        if (power > 0) {
            int i = 0;
            for (i = 0; i < power; i++) {
                result *= num;
            }
            return result;
        }
        else {
            if (power < 0) {
                power *= -1;
                int i = 0;
                for (i = 0; i < power; i++) {
                    result *= num;
                }
            }
            return 1 / result;
        }
    }
    int main(void)
    {
        double number;
        int p;
        printf("Enter a number to raise to a power : ");
        scanf("%lf", &number);
        printf("Enter the power to raise %.2lf to : ", number);
        scanf("%d", &p);
        printf("%.2f raised to the power of %d is : ", p);
        double result = power(number, p);
        double mathPow = pow(number, p);
        printf("\n%-20s%-20s\n", "My Function", "Pow() Function");
        printf("%-20.2f%-20.2f\n", result, mathPow);
        return 0;
    }
    // *** Your program goes here ***
    return 0;
} // end main()

Answer 1

您不能(或者至少不应该)在 C 语言的函数内定义函数。

cc -Wall -Wshadow -Wwrite-strings -Wextra -Wconversion -std=c99 -pedantic -g `pkg-config --cflags glib-2.0`   -c -o test.o test.c
test.c:15:41: error: function definition is not allowed here
    double power(double num, int power) {
                                        ^
test.c:36:5: error: function definition is not allowed here
    {
    ^

并且您有两个 main 函数。 main 是程序运行时由操作系统运行的函数。您只需要一个。

还有一些其他问题...

test.c:41:52: warning: format specifies type 'double' but the argument has type 'int' [-Wformat]
    printf("%.2f raised to the power of %d is : ", p);
            ~~~~                                   ^
            %.2d
test.c:41:42: warning: more '%' conversions than data arguments [-Wformat]
    printf("%.2f raised to the power of %d is : ", p);

那个printf缺少参数。应该是...

printf("%.2f raised to the power of %d is : ", number, p);

通过这些修复，它可以正常工作。

<小时/>

您可以DRY通过定义仅用于正数的第二个函数来提高功率。

double power_positive(double num, int power) {
    int i = 0;
    double result = 1;
    for (i = 0; i < power; i++) {
        result *= num;
    }
    return result;
}

double power(double num, int power) {
    if (power < 0) {
        return 1 / power_positive(num, -power);
    }
    else {
        return power_positive(num, power);
    }
}