/**
 * A class containing a method to calculate a root of a given function.
 *
 * @author Daniel Augurell och Viktor R�dmark
 * @group Labbgrupp 4
 * @assignement Lab 3 part 2
 * @date 2011-09-27
 *
 */
public class Secant {
    /**
     * Calculates a root of a given function between two given values.
     *
     * @param f The function
     * @param low The lower limit
     * @param high The higher limit
     * @param eps The accuracy of the calculation
     * @return The x value of the root
     */
    public static double secant(Function f, double low, double high, double eps) {
        double x = (high * f.f(low) - low * f.f(high)) / (f.f(low) - f.f(high));

        if (f.f(x + eps) * f.f(x - eps) > 0) {
            low = (f.f(x) < 0 ? x : low);
            high = (f.f(x) >= 0 ? x : high);
            x = secant(f, low, high, eps);
        }
        return x;
    }
}