double(*pfunction)() = &function;

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

double function(double x){
  return (double)(pow(x,3) + x/2 + 1);
}

double calc(double a, double b){
  double ha, hb, result=0;
  int i;
  double(*pfunction)() = &function; 
  for(i=0; i<1000; i++){
    ha = (*pfunction)(a+i*(b-a)/1000.0);
    hb = (*pfunction)(a+(i+1)*(b-a)/1000.0);
    result += ((ha + hb)*(b-a)/1000.0)/2.0;
  }
  return result;
}

void main(){
  double a = 0, b = 10, result;
  result = calc(a, b);
  printf("%lf", result);
}

2535.002500