c - 宽度不为 1 时的梯形规则程序未完成 (C)

Question

通过(上限 - 下限)/n(所需的梯形数)找到宽度的方式，在我的代码中，当宽度为 1 时它可以工作，但是如果它不是 1，程序将无法自行完成，我怀疑问题是我如何在“func”的 for 循环中递增它

代码:

#include <stdio.h>
#include <stdlib.h>

double func(double x) {
return x * x;
}

double trap(double lower, double upper, int n) {
double width,area = 0;

width = (upper - lower) / n;
//printf("%lf\n",width);

int i;
for (i = lower; i < upper; i += width) {
    area += (func(i) + ((func(i + width)))) / 2 * width;
    //printf("%lf\n",area);
}
return area;
}

int main(void) {

double lower,upper,x;
int n;


while (1) {

    printf("lower limit: ");
    scanf("%lf",&lower);
    printf("upper limit (should be greater than %.2lf): ",lower);
    scanf("%lf",&upper);

    if (upper <= lower) {
        printf("[ERROR] the lower limit must be less"); 
        printf("than the upper limit: please try again\n");
        continue;   
    }

    printf("number of trapezoids: ");
    scanf("%d",&n); 

    if (n <= 0) {
        printf("[ERROR] the number of trapezoids must be");
        printf("greater than 0; please try again\n");
        continue;
    }
    break;
}

printf("%lf\n", trap(lower,upper,n));



return 0;

Answer 1

问题在于循环增量。将宽度从 double 转换为 int 时，double 的小数部分将被丢弃。这会导致(不包含)-1.0 和 1.0 之间的任何宽度值转换为 0。