[Octave-bug-tracker] [bug #54622] test importdata fails in dev octave with windows

[Rik]

Follow-up Comment #61, bug #54622 (project octave):

The parser has its own rules.  See this ancient bug report from 2010
(https://savannah.gnu.org/bugs/?31974).  There has been no resolution there.

isalpha is better than tolower because it is checking for a positive
assertion.  The default, when given bizarre input such as EOF, will be return
false.

You are correct that '1+j' does not read correctly.  The issue is in dlmread
in the final else clause


else
{
  double y = octave_read_double (tmp_stream);

  if (! iscmplx && y != 0.)
    {
      iscmplx = true;
      cdata = ComplexMatrix (rdata);
    }

  if (iscmplx)
    cdata(i,j++) = Complex (x, y);
  else
    rdata(i,j++) = x;
}


For a construct like '1+2j' we have already read '1', and determined that the
next character ('+') is not a complex number indicator [iIjJ].  We have also
determined that it is not an alpha character and hence a corrupt text such as
"InfX".  So we pass the result to octave_read_double which would read "+2j"
and return 2.  That gets made in to a Complex value with the original number
in x and stored.  However, for '1+j', octave_read_double() returns 0 (default)
because there is no number in '+j'. 

This is definitely a corner case.  If there is an easy way to fix it we
should.  Otherwise, I wouldn't spend to much time on it.  Matlab's dlmread
function is very specific about the format it accepts for complex numbers


dlmread imports any complex number as a whole into a complex numeric field.
This table shows valid forms for a complex number.

Form                 Example

±<real>±<imag>i|j    5.7-3.1i

±<imag>i|j           -7j

Embedded white space in a complex number is invalid and dlmread regards it as
a field delimiter.


Octave can at least handle whitespace like "1 + 2j".

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