[wishlist] pkg require

[Francesco Potorti`]

>> Since, at least in 3.0, 'pg load' is so slow, even if the package is
>> already loaded, would it make sense to allow for loading a package if
>> not already loaded?
>>
>> Solution 1: 'pkg load' should only load a package if not already loaded,
>> unless an option -force is given that reloads the package.
>>
>> Solution 2: 'pkg load' accept a -require option which loads the package
>> only if not already loaded.
>>
>> Solution 3: 'pkg require' loads a package only if not already loaded.
>>
>Its not that simple.. "pkg load <package>" doesn't reload a package (ie 
>install on the path) if it is already installed. However, what it does 
>do is recursive check all of the dependencies of <package> to see if 
>they are loaded, and is very careful of the order in which packages are 
>placed on the path to handle the case that two packages install a 
>function with the same name or that the newly loaded package uses the 
>dependent package in its PKG_ADD file..

I see.  In my experience, that work takes time.  I still propose to add
a way to save that time.  From your description, it looks unsafe to do
it by default.  So I would retire my proposal #1 above, and keep #2 and
#3,  Maybe in #2, the option should be named -nocheck, or -quick rather
than -require.

Just as an example, I personally use this, which speeds things up a lot:

===File ~/math/octavelib/utils/pkgrequire.m=================
function pkgrequire (varargin)
  try pkglist = pkg("list");
  catch error("This is not Octave 3");
  end_try_catch

  for i = 1:nargin
    pkgname = varargin{i};
    found = false;
    for p = [pkglist]
      if (strcmp (pkgname, p{1}.name))
	found = true;
	if (!p{1}.loaded)
	  pkg ("load", pkgname)
	endif
	break;
      endif
    endfor
    if (!found)
      warning ("pkg_not_found", "Package %s not found", pkgname)
    endif
  endfor
endfunction
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Francesco Potortì (ricercatore)        Voice: +39 050 315 3058 (op.2111)
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