[Octave-bug-tracker] [bug #33876] textscan: resuming reading does not work

[Ben Abbott]

Follow-up Comment #5, bug #33876 (project octave):

Philip, thanks for the summary.

I thought I should mention that jwe plans to work on this part of the code,
But on a different problem. I think it is the same problem reported in the bug
here -> https://savannah.gnu.org/bugs/?33875

Oct 2010
Thread: advice / help needed for reading formatted text (textscan, strread, &
textread)
https://mailman.cae.wisc.edu/pipermail/octave-maintainers/2010-November/021513.html

I wrote another test script to help me understand how ML's implementation of
textscan() parses files. The isequal() checks each return true for ML.


filename = 'fubar.txt';
fid = fopen (filename, 'w');
for n = 1:2:20
  fprintf (fid, '%d %dn', n + [0 1])
endfor
fclose (fid);

fid = fopen (filename, 'r');
c1 = textscan (fid, '%d %d', 1);
c2 = textscan (fid, '%d %d', 2);
c3 = textscan (fid, '%d %d', 3);
fclose (fid);

isequal (c1, {[1] [2]})
isequal (c2, {[3; 5] [4; 6]})
isequal (c3, {[7; 9; 11] [8; 10; 12]})

fid = fopen (filename, 'r');
c1 = textscan (fid, '%d', 1);
c2 = textscan (fid, '%d %d', 3);
c3 = textscan (fid, '%d %d', 3);
fclose (fid);

isequal (c1, {1})
isequal (c2, {[2; 3; 5] [0; 4; 6]})
isequal (c3, {[7; 9; 11] [8; 10; 12]})

fid = fopen (filename, 'r');
c1 = textscan (fid, '%d', 5);
c2 = textscan (fid, '%d %d', 2);
c3 = textscan (fid, '%d %d %d', 3);
fclose (fid);

isequal (c1, {[1;2;3;4;5]})
isequal (c2, {[6;7], [0;8])
isequal (c3, {[9;11;13], [10;12;14], [0;0;0]})

delete (filename)


The patch I've attached (the 2nd one) functions correctly the first time the
file is read (the developers version does not).

The second and third examples have failures. In the second example, ML's
result reads "0" for c2{2}(1,1). Looking at the contents of fubar.txt ...


1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17 18
19 20


The "0"'s in both the 2nd and 3rd examples occur when textscan reads beyond an
EOL.


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