gfrepcov.m

数字通信第四版原书的例程

function p2 = gfrepcov(p1)
%GFREPCOV Converts GF(2) polynomial representation format.
%       Q = GFREPCOV(P) converts the representation format in GF(2).
%       A GF(2) polynomial A can be written in a descending order form:
%       A(X) = a_0 + a_1 X + ... a_n X^n
%       In GF(2), a_i is either zero or one. P is a vector that lists
%       all exponential powers in which a_i is a non-zero number. For
%       example, P=[0 5] means P(X) = 1 + x^5. Q is a vector that lists
%       all coefficient of Q(X). For example, Q = [1 0 0 0 0 1] means
%       Q(X) = 1 + X^5.
%
%       This function is written for GF(2) only.
%       
%       See also GFPRETTY.

%       Wes Wang 6/17/94, 10/7/95
%       Copyright (c) 1995-96 by The MathWorks, Inc.
%       $Revision: 1.1 $  $Date: 1996/04/01 17:59:45 $

if length([find(p1 == 1), find(p1 == 0)]) ~= length(p1)
    if (min(p1) < 0) | (max(p1 - ceil(p1)) > 0)
        error('Elements in P1 must be positive integer')
    end;

    % convert the second representation format to be first one.
    p1 = fliplr(sort(p1)) + 1;
    p2 = zeros(1, p1(1));
    for i = p1,
     % the even time of the assignement will make the coeficient zero.
        if p2(i)
            p2(i) = 0;
        else
            p2(i) = 1;
        end;
    end;
else
    p2 = p1;
end;

%--end of GFREPCOV--