为什么我的函数不修改 C 结构体中变量的值? [英] Why does my function not modify the value of variable in a struct in C?

问题描述

这是我的意见.我必须写一个函数，它给我减去 Zesp.Im

struct Zesp { double Re;双我;};struct Zesp z1 = { .Re = 5.323 ,.Im= 3.321};typedef struct Zesp zesp;zesp spZ(zesp z){z.Im = -(z.Im);返回 z;}int主(){spZ(z1);printf("%.2f, %.2f\n", z1.Re, z1.Im);返回0；}

我不知道为什么我得到的是 3.321 而不是 -3.321?

我编辑了我的程序，我的老师说我不能修改函数 spZ 的参数.

出现分段错误

<预><代码>#include struct Zesp { double Re;双我;};struct Zesp z1 = { .Re = 5.323 ,.Im= 3.321};typedef struct Zesp zesp;zesp spZ(zesp z){z.Im = -(z.Im);z = spZ(z);返回 z;}int主(){spZ(z1);printf("%.2f, %.2f\n", z1.Re, z1.Im);返回0；}

解决方案

您正在将结构的副本传递给函数.它返回一个副本，但您没有使用结果.

您需要将函数的结果赋给变量.

z1 = spZ(z1);

This is my input. I must write a function, which give me minus Zesp.Im

struct Zesp { double Re; 
                    double Im; 
                };
struct Zesp z1 = { .Re = 5.323 ,.Im= 3.321};
typedef struct Zesp zesp;

zesp spZ(zesp z)
{
    z.Im = -(z.Im);
    
    return z;
}

int main ()
{
    spZ(z1);
    printf("%.2f, %.2f\n", z1.Re, z1.Im);
    return 0;
}

I don't know why I get 3.321 instead of -3.321?

I edit my program, my teacher said that I can't modify argument of a function spZ.

I get a segmentation fault

#include <stdio.h>

struct Zesp { double Re; 
                    double Im; 
                };
struct Zesp z1 = { .Re = 5.323 ,.Im= 3.321};
typedef struct Zesp zesp;

zesp spZ(zesp z)
{
    z.Im = -(z.Im);
    z = spZ(z);

    return z;
}

int main ()
{
    spZ(z1);
    printf("%.2f, %.2f\n", z1.Re, z1.Im);
    return 0;
}

解决方案

You're passing a copy of the structure to the function. It returns a copy, but you're not using the result.

You need to assign the result of the function to the variable.

z1 = spZ(z1);

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