Re: explanation what "error: can't redefine read-only symbol foo" means in detail

[John W. Eaton]

On  6-Mar-2007, Andreas Romeyke wrote:

| Hi,
| 
| David Bateman wrote:
| > So I don't see what the problem is. Can you give a full example...
| >   
| The problem is that the original function comes from Matlab and dies on
| Octave with error message above. I do not understand why this message is
| generated, because the function is large but not too complicated.
| 
| Therefore it would be helpful to have an example that generates  the
| message above. The function is from the EEGLab toolbox and is called
| eeg_checkset(). The m-file is attached, it dies on line 925.
| 
| Here the output:
| 
|     Extracting events...
|     Importing data events...
|     Removing event channel...
|     error: can't redefine read-only symbol `eeg_checkset'
|     error: `eeg_checkset' undefined near line 925 column 25
|     error: evaluating switch command near line 837, column 9
|     error: evaluating for command near line 836, column 5
|     error: evaluating if command near line 835, column 1
|     error: called from `eeg_checkset' in file
|     `/SCR/svn_work/eeglab-devel-5.03/eeglab5.03/functions/eeg_checkset.m'
|     error: evaluating assignment expression near line 234, column 9
|     error: evaluating if command near line 226, column 1
|     error: called from `pop_biosig' in file
|     `/SCR/svn_work/eeglab-devel-5.03/eeglab5.03/functions/pop_biosig.m'
|     error: evaluating assignment expression near line 10, column 5
| 
| Could it be that the problem depends on type of variable, because the
| EEG-variable is global by default (set in toolbox)?
| 
| Any hints?

I tried running your file and I see

  octave2.9:1> eeg_checkset
  error: `argn' undefined near line 0 column 10
  error: evaluating argument list element number 1
  error: evaluating assignment expression near line 13, column 5
  error: called from `inputname' in file 
`/usr/share/octave/2.9.9/m/miscellaneous/inputname.m'
  error: evaluating argument list element number 2
  error: evaluating assignment expression near line 742, column 5
  error: called from `eeg_checkset' in file `/tmp/eeg_checkset.m'

so it does not seem to be a complete example.  It looks like
eeg_checkset is intended to be called from another function in eeglab,
so calling it from the command line with no arguments fails.  How am I
supposed to call eeg_checkset so that I can reproduce the problem?  If
you send something that we can actually run then maybe we can help.
But please try to pare it down to a small example that demonstrates
the problem.

jwe