horner.cpp

datastucutre and algorithms, application, in C

// evaluate a polynomial using Horner's rule

#include <iostream>
#include <algorithm> // has copy

using namespace std;


template<class T>
T horner(T coeff[], int n, const T& x)
{// Evaluate the degree n polynomial with
 // coefficients coeff[0:n] at the point x.
   T value = coeff[n];
   for (int i = 1; i <= n; i++)
      value = value * x + coeff[n - i];
   return value;
}

int main()
{
   int a[6] = {1, 2, 3, 4, 5, 6};

   // output the coefficients
   cout << "The coefficients a[0:5] are ";
   copy(a, a+6, ostream_iterator<int>(cout, " "));
   cout << endl;

   cout << "The value at 2 is " << horner(a,5,2) << endl;
   cout << "The value at 1 is " << horner(a,5,1) << endl;
   cout << "The value at 0 is " << horner(a,5,0) << endl;
   return 0;
}