namespace support revisited

[jaeandersson]

Hi,

I'd like to revisit the topic of namespace support, cf. the following thread
from early 2010:
http://octave.1599824.n4.nabble.com/namespace-support-td1638758.html

Has there been any progress on this since then? The proposed solution in
that thread is rather hacky and does not work if you try to alias a class
instead of a function. I think a proper "import.m" function can be
implemented much simpler than that, namely as follows:


function varargout = import(varargin)
  persistent imported;
  if ~iscell(imported)
    imported = cell(0, 1);
  end
  if nargin==0
     varargout{1} = imported;
  else
    for i=1:nargin
      imported{end+1} = varargin{i};
    end
  end
end


This would need to be coupled to some mechanism that calls "import" with no
arguments whenever a symbol is missing. But I don't know how such a
mechanism can be implemented. Or if it can be implemented at all without
changing the Octave source.


I also came up with a hacky solution that works when you want to issue a
command such as "import mypackage.*", which unlike the solution in the older
thread handles the wildcard chararcters and (sort of) works when the package
contains classdef classes:


function import(varargin)
 error(nargchk(1, inf, nargin, 'struct'));
 for i=1:nargin
   import1(varargin{i});
 end
end

function import1(pkgname)
  % Split up name into parts
  pkgname_parts = strsplit(pkgname, '.');
  % Fallback to system import command if not entire package (i.e. failure)
  if length(pkgname_parts)~= 2 || ~strcmp(pkgname_parts{end}, '*')
    error('Only the syntax ''import package_name.*'' is currently
supported')
  end
  % Get path for package
 pkgpath = locatepkg(pkgname_parts{1});
  % Add to path
  addpath(pkgpath);
end

function pkgpath = locatepkg(pkgname)
 pathdirs = strsplit(path, pathsep);
 for iPath=1:length(pathdirs)
   pkgpath = [pathdirs{iPath} filesep '+' pkgname];
   if exist(pkgpath, 'dir')
     return;
   end
 end
 error('Package ''%s'' cannot be located in the path', pkgname);
end

But again, this is a hacky solution. I think that a proper solution, that
works for "import mypackage.*" as well as "import mypackage.myclass" and
"import mypackage.myfunction", should look like the first snippet above,
coupled to some mechanism for alias lookup.

Best regards,
Joel



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