一个求函数的积分的程序执行问题

Question

#define _CRT_SECURE_NO_DEPRECATE

#include

double integrate(double, double, int);

double equa(double); /*函数说明，背积函数，具体函数可替换*/

float a, b, c;

void main() {

double  leftlimit, rightlimit;/*积分上限，下限*/

int  n;/*梯形划分数*/  

printf("请输入被积分函数的系数：a,b,c:\n");

scanf("%f%f%f", &a, &b, &c);

printf("请输入被积分函数的上限及下限：\n");

do {

    scanf("%lf%lf", &leftlimit, &rightlimit);

    if (leftlimit > rightlimit)  printf("积分下限应该小于上限，请重新输入：");


} while (leftlimit < rightlimit);

printf("请输入被积分函数的划分数（要求正整数）：\n");


getchar();
scanf("%d", &n);

if (n < 0)  n = -n;/*对用户输入的负整数进行取正*/

printf("积分结果为=%.2f\n", integrate(leftlimit, rightlimit,n));


system("pause");

}
/*积分求解函数*/

double integrate(double lower, double upper, int n) {

double  h, si, area = 0;

int  i;

h = (upper - lower) / n;

for (i = 0;i < n;i++) {

    si = h*(equa(lower + i*h) + equa(lower + (i + 1)*h)) / 2;

    area = si + area;


}

return  area;

}

/*被积函数*/

double equa(double xi) {

return   a*xi*xi + b*xi + c;

}

Answer 1

这段函数写的有问题

  do
    {

        scanf("%lf%lf", &leftlimit, &rightlimit);

        if (leftlimit > rightlimit)  printf("积分下限应该小于上限，请重新输入：");


    }
    while (leftlimit < rightlimit);