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#include <matrix/math.hpp>

#ifndef EKF_UTILS_HPP
#define EKF_UTILS_HPP

// Use Kahan summation algorithm to get the sum of "sum_previous" and "input".
// This function relies on the caller to be responsible for keeping a copy of
// "accumulator" and passing this value at the next iteration.
// Ref: https://en.wikipedia.org/wiki/Kahan_summation_algorithm
inline float kahanSummation(float sum_previous, float input, float &accumulator)
{
	const float y = input - accumulator;
	const float t = sum_previous + y;
	accumulator = (t - sum_previous) - y;
	return t;
}

namespace ecl
{
inline float powf(float x, int exp)
{
	float ret;

	if (exp > 0) {
		ret = x;

		for (int count = 1; count < exp; count++) {
			ret *= x;
		}

		return ret;

	} else if (exp < 0) {
		return 1.0f / ecl::powf(x, -exp);
	}

	return 1.0f;
}

} // namespace ecl

#endif // EKF_UTILS_HPP