Question

我无法弄清楚如何在下面的代码中添加指针。我是结构新手，并没有太多接触它们。我需要能够通过引用将值传递给函数。我不一定需要代码只是一个关于我如何去做或指向正确方向的想法。感谢。

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

union Data1
{
    double x1;
};
union Data2
{
    double x2;
};
struct array
{
    int n[7];
    int sums[7];
    int sumt[7];
};

double f(double x);
double simp(int n, double x1, double x2);
double trap(int n, double x1, double x2);

int main()
{
    union Data1 data1;
    union Data2 data2;
    struct array array1;
    int i;
    FILE *f;

    f = fopen("data.dat", "a");

    data1.x1 = -INFINITY;
    data2.x2 = INFINITY;


    printf ("Both integration techniques will run for the following intervals: 1, 10, 25, 50, 100, 1000, 10000\n");
    array1.n[0] = 1;
    array1.n[1] = 10;
    array1.n[2] = 25;
    array1.n[3] = 50;
    array1.n[4] = 100;
    array1.n[5] = 1000;
    array1.n[6] = 10000;

    for(i=0;i<7;i++)
    {
    array1.sums[i] = simp(array1.n[i],data1.x1,data2.x2);
    array1.sumt[i] = trap(array1.n[i],data1.x1,data2.x2);
    }


    printf("For the trap rule:\n");
    printf("\t\tN\t\t\tSum\n");
    for(i=0;i<7;i++)
    {
       printf("\t\t%d\t\t\t%d\n",array1.n[i],array1.sumt[i]);
    }

    printf("For the simpson rule:\n");
    printf("\t\tN\t\t\tSum\n");
    for(i=0;i<7;i++)
    {
       printf("\t\t%d\t\t\t%d\n",array1.n[i],array1.sums[i]);
    }

    fprintf(f, "For the simpson rule:\n");
    fprintf(f,"\t\tN\t\t\tSum\n");
    for(i=0;i<7;i++)
    {
       fprintf(f,"\t\t%d\t\t\t%d\n",array1.n[i],array1.sums[i]);

    }
    fprintf(f,"For the trap rule:\n");
    fprintf(f,"\t\tN\t\t\tSum\n");
    for(i=0;i<7;i++)
    {
       fprintf(f,"\t\t%d\t\t\t%d\n",array1.n[i],array1.sumt[i]);
    }
    fclose(f);

    return 0;

}

double f(double x)
{
    double y;

    y = exp(-pow(x,2));

    return y;
}

double simp(int n, double a, double b)
{
    int i;
    double dx, x, sum;

    dx = (b-a)/n;
    sum = f(a)+ f(b);
    for(i=1;i<n;i++)
    {
        x = a + dx*i;
        sum += 2*(1+i%2)*f(x);
    }
    sum*=dx/3;
    return sum;
}

double trap(int n, double a, double b)
{
    int i;
    double dx, x, sum;

    dx=(b-a)/n;
    sum = f(a)+f(b);
    for(i=1;i<n;i++)
    {
        x = a + dx*i;
        sum += 2*f(x);
    }

    sum *= dx/2;
    return sum;
}

Answer 1

您尝试使用的语法是初始化。但是你没有初始化，你正在分配。初始化只能在定义变量时完成。

所以你需要这样做：

struct array array1 = {{1,10,25,50,100,1000,10000},{0},{0}};

这会将数组n初始化为所需的值，并将sums和sumt的所有值初始化为0.

Answer 2

要添加指向结构的指针，你可以这样做：

struct array* array1Pointer = &array1;

然后你可以将array1Pointer传递给你想要的函数。

或者你可以在开头声明一个指针，然后为它指向的对象赋值：

struct array* array1Pointer = malloc(sizeof(struct array));

array1Pointer->n[0] = 1;
array1Pointer->sums[i] = simp(array1Pointer->n[i], data1.x1, data2.x2);

带指针的结构问题

2 个答案: