LagrangeInterpolation.h

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#ifndef TIL_LAGRANGE_INTERPOLATION_H
#define TIL_LAGRANGE_INTERPOLATION_H

// includes from TIL library
#include "til/til_common.h"
#include "til/labels.h"

namespace til
{

  // NOTE: The templating has been done on the function members rather than on
  // the class itself, to make use of the automatic template deduction of functions.
  // It may be changed.
  template < typename T >
        class Lagrange4Interpolation
    : public Interpolator_label
        {
        public: // static members ---------------------------------------------------

                // NB: There is a priori no reason for f to be the same type as x.
                // However, forcing x and f to have the same type forces the
                // (necessary anyway) casting to be done once, before function
                // call.
                inline static T compute(
                T f1,   
                T f2,   
                T f3,   
                T f4,   
                T x             
                )
                {
                        return (((3*(f2-f3)+f4-f1)/6.0*x+((f1+f3)/2.0-f2))*x+(6*f3-2*f1-3*f2-f4)/6.0)*x+f2;
                }
        };

}

#endif