Suppose the file data.txt contains the lines
Is there an expected output of the following script
fid = fopen('data.txt');
[v, n] = fscanf(fid, '%f');
ftell(fid)
fclose(fid);
? Obviously, the FSCANF call will fail to convert any floating point numbers upon encountering the '--' string whence isempty(v) and n==0. However, I'm currently most concerned about the FTELL call. In MATLABs 7.7 (R2008b) and 7.9 (R2009b), FTELL returns 1 while MATLABs 7.10 (R2010a) and 7.13 (R2011b) both return 0.
In other words, R2009b (and earlier editions) advances the file pointer one byte, presumably because '-' is a valid leading character sequence of a (negative) floating point number. Later M-editions do apparently not advance the file pointer however, presumably because '--' is not a valid leading character sequence of a floating point number.
So, to repeat my above question: is there any defined behaviour with respect to FTELL in case of FSCANF conversion failure and, if so, did this behaviour change between R2009b and later editions of MATLAB? I cannot find anything in doc fscanf, doc ftell or the release notes.
As far as I can tell, MathWorks Technical Solution ID 1-426ARH is related to this question, but does not appear to be exactly the same thing. Am I just misreading the information therein?
PS Before you ask: For various reasons (unrelated to this particular issue) I cannot simply use
textscan(fid, '%f', 'CommentStyle', '--')
in the general case I'm trying to solve.
