#include"stdio.h"#include"math.h"int main(){float integral(float(*)(float),float,float,int); //声明一个float的指针函数返回值是float，2个float参数，1个int参数的函数。float fsin(float);float fcos(float);float fexp(float);float a1,b1,a2,b2,a3,b3,c,(*p)(float); //定义一个float类型的指针。int n=20;printf("enter a1,b1: "); //输入积分上下限。scanf("%f %f",&a1,&b1);printf("enter a2,b2: ");scanf("%f %f",&a2,&b2);printf("enter a3,b3: ");scanf("%f %f",&a3,&b3);p=fsin; //是float型指针变量指向fsin函数。c=integral(p,a1,b1,n);printf("sin(x)=%f\n",c);p=fcos;c=integral(p,a2,b2,n);printf("cos(x)=%f\n",c);p=fexp;c=integral(p,a3,b3,n);printf("exp(x)=%f\n",c);return 0;}float integral(float(*p)(float),float a,float b,int n){int i;float x,h,s; h=(b-a)/n;//把积分区间分成n段，每段等长。x=a;s=0;for(i=0;i<n;i++){x=x+h;s=s+(*p)(x)*h; //积分值等于20个矩形区间面积的和}return (s);}float fsin(float x){return sin(x);}float fcos(float x){return cos(x);}float fexp(float x){return exp(x);}
