class RootFinder:
    # This class provides methods for solving one-dimensional problems 
    # of the kind: find a root x of f(x) = 0.
    def __init__(self,kernel,algorithm):
        self.kernel = kernel
        self.algo   = algorithm

    def setKernel(self,kernel):
        self.kernel = kernel

    def solveFor0(self,accuracy):
        if self.algo=='NR':
            return self.NewtonRaphson(accuracy);
        print 'Cannot solve for kernel = 0 in algorithm ',self.algo,';'
        print 'algorithm is not implemented.'
        return None

    def NewtonRaphson(self,accuracy):
        # An implementation of the Newton-Raphson method to
        # solve f(x) = 0.
        # Trial solutions are produced with help of the function
        # and its first derivative.  The iterative procedure should
        # stop if |x_{i+1}-x_i|/|x_{i+1}+x_i| < 2 accuracy
        # Fix this.
        return 0.