Octave 2.1.55: wrong type argument `matrix'

[Paul C. Leopardi]

Hi,
I'm porting a set of Matlab scripts to Octave 2.1.55, and have encountered the 
following error message:

error: octave_base_value::list_value(): wrong type argument `matrix'
error: evaluating assignment expression near line 22, column 15
error: evaluating if command near line 19, column 1

The offending code is in the file expand_region_for_diam.m

 1  function expanded_region = expand_region_for_diam(region)
15  fuzz = 100*eps;
16  dim = size(region,1);
17  s_top = region(dim,1);
18  s_bot = region(dim,2);
19  if dim > 1
20   region_1 = expand_region_for_diam(region(1:dim-1,:));
21   expanded_region = [append(region_1, s_top), append(region_1, s_bot)];
22  else
23   if s_bot == 0
24    s_bot = 2*pi;
25   end
26   if (mod(s_bot - s_top, 2*pi) < fuzz) || (mod(s_bot - s_top, 2*pi) > pi)
27    s_bot = s_top + pi;
28   end
29   expanded_region = [s_top, s_bot];
30  end

The function append is defined in append.m

function result = append(A,value)
result = [A; ones(1,size(A,2))*value];

1. What does the error message
"error: octave_base_value::list_value(): wrong type argument `matrix'"
mean?

2. What am I doing wrong and how do I fix it?

3. Have I found a bug in Octave?



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