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/* Boost example/horner.cpp
* example of unprotecting rounding for a whole function computation
*
* Copyright 2002-2003 Guillaume Melquiond
*
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or
* copy at http://www.boost.org/LICENSE_1_0.txt)
*/
#include <boost/numeric/interval.hpp>
#include <iostream>
// I is an interval class, the polynom is a simple array
template<class I>
I horner(const I& x, const I p[], int n) {
// initialize and restore the rounding mode
typename I::traits_type::rounding rnd;
// define the unprotected version of the interval type
typedef typename boost::numeric::interval_lib::unprotect<I>::type R;
const R& a = x;
R y = p[n - 1];
for(int i = n - 2; i >= 0; i--) {
y = y * a + (const R&)(p[i]);
}
return y;
// restore the rounding mode with the destruction of rnd
}
template<class T, class Policies>
std::ostream &operator<<(std::ostream &os,
const boost::numeric::interval<T, Policies> &x) {
os << "[" << x.lower() << ", " << x.upper() << "]";
return os;
}
int main() {
typedef boost::numeric::interval<double> I;
I p[3] = { -1.0, 0, 1.0 };
I x = 1.0;
std::cout << horner(x, p, 3) << std::endl;
return 0;
}
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