// TODO: Add licence
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL:$
// $Id:$
// 
//
// Author(s)     : 
// 
// ============================================================================

#ifndef CGAL_POLYNOMIAL_IPOWER_H
#define CGAL_POLYNOMIAL_IPOWER_H

CGAL_BEGIN_NAMESPACE

template <typename NT>
inline
NT ipower(const NT& base, int expn) {
    // compute base^expn using square-and-multiply
    CGAL_precondition(expn >= 0);
    
    // handle trivial cases efficiently
    if (expn == 0) return NT(1);
    if (expn == 1) return base;
    
    // find the most significant non-zero bit of expn
    int e = expn, msb = 0;
    while (e >>= 1) msb++;
    
    // computing base^expn by square-and-multiply
    NT res = base;
    int b = 1<<msb;
    while (b >>= 1) { // is there another bit right of what we saw so far?
        res *= res;
        if (expn & b) res *= base;
    }
    return res;
}


CGAL_END_NAMESPACE

#endif // CGAL_POLYNOMIAL_IPOWER_H