Honerの方法

/* 
 * -----------------------------
 * Hornerの方法
 * -----------------------------
 */
#include <stdio.h>
double fn(double, double *, int);
void main(void){
    double a[] = {1, 2, 3, 4, 5};
    double x;

    for(x=1;x<=5;x++){
        printf("fn(%f)=%f¥n", x, fn(x, a, 4));
    }
}
double fn(double x, double a[], int n){
    double p;
    int i;

    p=a[n];
    for(i=n-1; i>=0; i--){
        p=p*x+a[i];
    }
    return p;
}