| Re: XSTRETCH and Library Lessons [message #48531 is a reply to message #48472] |
Wed, 26 April 2006 06:34   |
mmiller3
Messages: 81
Registered: January 2002
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Member |
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>>>> > "JD" == JD Smith <jdsmith@as.arizona.edu> writes:
[much text snipped...]
> Another way of thinking about it... how would you recommend
> fixing the originally proposed XSTRETCH problem using !PATH
> alone? The solution has to allow me to run XSTRETCH, and
> the other random code which contain shadowing routines (by
> now quite obsolete and incompatible), all in the same
> session.
Hi JD,
I see your point. My recommendation was that the IDL_PATH needs
to be set "right," but that really boils down to "that's the only
way I know how to handle it with existing IDL."
The simplest way to handle fine tuning of paths, again with the
current IDL (and I encourage my colleagues to avoid this at all
costs!) is to explicitly .compile or .run files (not routines!)
with the full path specified. This makes code very unportable
though - and I've spent plenty of time frustrated about why my
changes don't seem to have any effect, only to find someone has
slipped an absolute path into some code somewhere.
If I had my choice, I'd go with versioned imports and flexible
name spaces, like you suggested, so I could do something like
"import AstroLib" to get the default versions of the whole
collection. Then I'd use elements of AstroLib with calls
something like x = AstroLib.calculate_x(). If I wanted Foo from
the default version, I'd have it. If I wanted Bar from another
version, I'd like to be able to add Bar to the AstroLib name
space (or replace it, if it is already there) with something like
"import AstroLib-other-version.Bar as AstroLib.Bar". Then calls
to AstroLib.Bar would not have to be changed in any code, but I
could get them from what ever version I want.
In the absence of a name space mechanism, maybe this could be
implemented by installing multiple versions of libraries in a
directory tree something like this:
IDL_lib_root -- AstroLib -+- default (link to latest/prefered version)
+- 1.0 (contains version 1.0 files)
+- 1.1 ...
...
\- 27.0 (contains latest and greatest...)
If I adhere to the name-files-so-IDL-can-automatically-find-
and-compile-routines rule, the initial import of AstroLib can be
done with
pro install_library, lib, version=version, root=root
if n_elements(root) ne 1 then root='/local/IDL/lib/install/dir/'
if n_elements(version) eq 1 then begin
!path = root + lib + '/' + version ':' + !path
endif else begin
!path = root + lib + '/default:' + !path
endelse
end
Replacing routines with other versions, could be done with
something like
pro replace_library_routine, lib, routine, version=version, _extra=extra_keywords
current_path = !path
if n_elements(version) ne 1 then version='default'
install_library, lib, version, _extra=extra_keywords
resolve_routine, routine
!path = current_path
end
From the command line, or start up script, or where ever, I can
do
IDL> install_library, 'AstroLib'
Now all the AstroLib routines are available to me by name.
Replacing Bar with version 1.0 and Foo with my local modification
(installed in a similar tree somewhere else...), could be done
with
IDL> replace_library_routine, 'AstroLib', 'Bar', version='1.0'
IDL> replace_library_routine, 'AstroLib', 'Foo', version='mine', $
root='/home/me/lib/IDL/AstroLib'
Later on, when I realize that my local changes are really not so
usefull, I can go back to the default version with
IDL> replace_library_routine, 'AstroLib', 'Foo'
I certainly haven't thought this out enough to see where it would
or would not work! (I'm still on my first bit of coffee for the
day :-)
Mike
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