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48 lines
1.4 KiB
C++
48 lines
1.4 KiB
C++
/* Boost example/horner.cpp
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* example of unprotecting rounding for a whole function computation
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*
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* Copyright Guillaume Melquiond 2002-2003
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* Permission to use, copy, modify, sell, and distribute this software
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* is hereby granted without fee provided that the above copyright notice
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* appears in all copies and that both that copyright notice and this
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* permission notice appear in supporting documentation.
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*
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* None of the above authors nor Polytechnic University make any
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* representation about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied warranty.
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*
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* $Id$
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*/
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#include <boost/numeric/interval.hpp>
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#include <boost/numeric/interval/io.hpp>
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#include <iostream>
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// I is an interval class, the polynom is a simple array
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template<class I>
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I horner(const I& x, const I p[], int n) {
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// initialize and restore the rounding mode
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typename I::traits_type::rounding rnd;
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// define the unprotected version of the interval type
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typedef typename boost::numeric::interval_lib::unprotect<I>::type R;
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const R& a = x;
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R y = p[n - 1];
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for(int i = n - 2; i >= 0; i--) {
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y = y * a + (const R&)(p[i]);
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}
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return y;
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// restore the rounding mode with the destruction of rnd
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}
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int main() {
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typedef boost::numeric::interval<double> I;
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I p[3] = { -1.0, 0, 1.0 };
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I x = 1.0;
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std::cout << horner(x, p, 3) << std::endl;
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return 0;
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}
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