You can do it the hard way:
Open the file prefdir\matlab.prf. Search for the variable "Editor.Language.MATLAB.Extensions" and append 'xtn'.
Ext = 'xtn';
PrefFile = fullfile(prefdir, 'matlab.prf');
copyfile(PrefFile, [PrefFile, '.bak']); % To be secure
fid = fopen(PrefFile, 'r');
if fid == -1
error('Cannot open file for reading: %s', PrefFile);
end
C = textscan(fid, '%s', 'Delimiter', '\n');
Data = C{1};
fclose(fid);
key = 'Editor.Language.MATLAB.Extensions';
index = strncmp(Data, key, length(key));
if sum(index) ~= 1
error('Cannot identify key line.');
end
keyLine = Data{index};
keyData = keyLine(length(key) + 3:end); % <key>=S...
keyValue = regexp(keyData, ';', 'split');
if ~any(strcmpi(keyValue, Ext))
keyData = [keyData, ';', Ext];
end
Data{index} = [key, '=S', keyData];
% Save the file:
fid = fopen(PrefFile, 'w');
if fid == -1
error('Cannot open file for writing: %s', PrefFile);
end
fprintf(fid, '%s\n', Data{:});
fclose(fid);
Afterwards restart Matlab:
!matlab
quit
Or you use the smart, but undocumented methods:
key = 'Editor.Language.MATLAB.Extensions';
keyData = com.mathworks.services.Prefs.getPref(key);
keyValue = regexp(keyData, ';', 'split');
if ~any(strcmpi(keyValue, Ext))
keyData = [keyData, ';', Ext];
com.mathworks.services.Prefs.setStringPref(key, keyData);
end
This worked 2007 (see http://mathworks.com/matlabcentral/newsreader/view_thread/154608) and in R2011b. But as all undocumented methods this might change in the future.
Finally, let me mention, that this does not look like a useful method to me. I guess that it is easier to change the file extension from the concerned files.
