arithcode.m

function enc = arithcode(inx, a)
    N = 22;
    P = 8;
    C = 0;
    A = 2^N;
    r = -1;
    b = 0;
    enc = [];
    
    pc= floor(a * 2^P);
    ps = floor((1-a) * 2^P);
    pre = inx(1);

    for xn = inx
        if xn ~= pre
            T = A * pc;
            C = C + 0;
        else
            T = A * ps;
            C = C + T;
        end
        if C >= 2^(N+P)
            C = mod(C, 2^(N+P));
            enc = [enc 1];
            if r > 0
                enc = [enc zeros(1,r-1)];
                r = 0;
            else
                r = -1;
            end
        end
    
        while T < 2^(N+P-1)
            b = b + 1;
            T = 2 * T;
            C = 2 * C;
            if C >= 2^(N+P)
                C = mod(C, 2^(N+P));
                if r < 0
                    enc = [enc 1];
                else
                    r = r + 1;
                end
            else
                if r >= 0
                    enc = [enc 0 ones(1,r)];
                end
                r = 0;
            end
        end
        A = floor(T / 2^P);
        pre = xn;
     end
    
    if r >= 0
        enc = [enc 0 ones(1,r)];
    end
    
    tc = dec2binvec(C);
    if length(tc) > (N + P)
        tc = tc(end-(N+P)+1:end); 
    else
          hl=N+P-length(tc);
          tc=[tc zeros(1,hl)];
    end

    enc = [enc tc]; 
end