指向函数指针

//指向函数的指针 函数类型 (*指针变量名)(参数列表);
#include <stdio.h>
#include <math.h>

//integal(x^2)
double func1(double a, double b)
{
double sum = 0.0;
double length = 0.000001;
double x = a;
while ( x < b)
{
sum += x * x * 0.000001;
x += 0.000001;
}

return sum;
}
//integal(sinx)
double func2(double a, double b)
{
double sum = 0.0;
double length = 0.000001;
double x = a;
while ( x < b)
{
sum += sin(x) * 0.000001;
x += 0.000001;
}

return sum;
}
//integal(e^(x^-2)
double func3(double a, double b)
{
double sum = 0.0;
double length = 0.000001;
double x = a;
while ( x < b)
{
sum += exp(sqrt(x)) * 0.000001;
x += 0.000001;
}

return sum;
}
void integal(double a, double b, double (*fun)(double, double))
{
double result = 0.0;
result = (*fun)(a, b);
printf("%g/n", result);
}

void main()
{
printf("计算x^2在0~1上的定积分结果: ");
integal(0.0, 1.0, func1);
printf("计算sinx在0~π上的定积分结果: ");
integal(0.0, 3.141593, func2);
printf("计算e^(x^-2)在0~1上的定积分结果: ");
integal(0.0, 1.0, func3);
}