function [ x, dp2, p1 ] = gen_laguerre_ss_root ( x, order, alpha, b, c ) %*****************************************************************************80 % %% GEN_LAGUERRE_SS_ROOT improves an approximate root of a generalized Laguerre polynomial. % % Licensing: % % This code is distributed under the GNU LGPL license. % % Modified: % % 20 February 2008 % % Author: % % Original FORTRAN77 version by Arthur Stroud, Don Secrest. % MATLAB version by John Burkardt. % % Reference: % % Arthur Stroud, Don Secrest, % Gaussian Quadrature Formulas, % Prentice Hall, 1966, % LC: QA299.4G3S7. % % Parameters: % % Input, real X, the approximate root, which % should be improved on output. % % Input, integer ORDER, the order of the polynomial to be computed. % % Input, real ALPHA, the exponent of the X factor. % % Input, real B(ORDER), C(ORDER), the recursion coefficients. % % Output, real X, the approximate root, which % should be improved on output. % % Output, real DP2, the value of L'(ORDER)(X). % % Output, real P1, the value of L(ORDER-1)(X). % maxstep = 10; eps = r8_epsilon ( ); for i = 1 : maxstep [ p2, dp2, p1 ] = gen_laguerre_ss_recur ( x, order, alpha, b, c ); d = p2 / dp2; x = x - d; if ( abs ( d ) <= eps * ( abs ( x ) + 1.0 ) ) return; end end return end