Re: octave to matlab conversion

[Paul Kienzle]

On Oct 8, 2005, at 4:40 AM, A S Hodel wrote:

> On Oct 7, 2005, at 8:23 PM, Joe Koski wrote:
> > My opinion is that the perfect mat2oct or oct2mat converter (other 
> > than a
> > knowledgeable human) will never exist because of major differences 
> > between
> > the MATLAB toolboxes and octave-forge. There will never be a good 
> > one-to-one
> > equivalency. Both collections will continue to have their strengths 
> > and
> > weaknesses.
>
> I firmly agree with Joe here.  MATLAB and Octave are both moving 
> targets.  How many people have upgraded from Matlab 4 to 5, 5 to 6, 
> and 6 to 7, only to discover that some formerly functional m-files or 
> compiled mex-functions have to be rewritten?  Even in Octave, we see 
> changes from time to time (e.g., deprecation of gset).  If such a 
> converter were written, it would require regular maintenance as 
> features are added to the two systems.

Yes the 'moving target' problem is a pain.  The solution in Tcl/Tk is 
that "package require" can request a specific version.  So for example, 
if you have a script use system 5.0 function interfaces then you could 
"package require system 5.0".  A similar thing will be possible in 
octave if/when there is some sort of namespace support.  This won't 
protect against changes in syntax without cruft in the core.  Tricky 
issues are things such as the change over from indexing accepting real 
values to indexing requiring integers.

> I use Octave and MATLAB when teaching my classes in electrical 
> engineering.  With the aid of Octave-forge, I am able to write scripts 
> that will work in both systems.  Nevertheless, at some point in a 
> given project one may need to make a commitment to one or the other.  
> That's where the strengths and weaknesses discussed above come into 
> play.

When I wrote the converter (I needed my signal processing functions 
working with matlab) I included a simple macro processor which handled 
tags such as:

        title('hello');      %octave
        plot(1:10,1:10);
    %title('hello');     %matlab

When converting, the percent was removed from the beginnings of lines 
contain %matlab and added to the beginnings of lines containing 
%octave.  I don't remember the exact syntax.  I may have had some 
version numbering in there as well.

Together with %! test scripts to check that the conversion was 
successful, it was not a lot of work to support both systems 
simultaneously.

- Paul



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