Re: [Xotcl] nested objects in nx

From: Gustaf Neumann <neumann_at_wu-wien.ac.at>
Date: Fri, 29 Oct 2010 09:56:23 +0200

Dear victor,

There is a difference/asymmetry between
"namespace path" and "namespace import"

* "namespace import" creates cmd-stubs in the actual namespace
    (if issued on "::", in the top-level namespace). The
default rule
    for function resolving checks the contents of the top-level
    namespace as a final resort.

* "namespace path" adds a searchpath to the current namespace,
    but this is apparently not used as "final resort rule".

Look at the following test script, which is pure tcl:
  - the namespace ::tst contains two procs, f-1 is
     namespace-imported to top, f-2 not (just
     namespace-pathed).
   - Both are seen by a toplevel "info command",
     both can be executed on top.
   - in the ::app-namespace, we have no
     namespace path. We can call f-1, but not f-2

===================================
namespace eval ::tst {
   proc f-1 {} { return f-1 }
   proc f-2 {} { return f-2 }
   namespace export f-1 f-2
}

namespace path tst
namespace import tst::f-1
puts f-1=[namespace which f-1]
puts f-2=[namespace which f-2]
puts "we see: [info command f-*]"

namespace eval ::app {
   proc foo {} {
     puts [namespace current]//[namespace path]
     puts f-1=[namespace which f-1]
     puts f-2=[namespace which f-2]
     f-1
     f-2
   }
}

::app::foo
===================================

Exactly the same happens in "a::b tst", since "::a"
is an object with object-specific methods and
establishes a tcl namespace.

% Object create a
::a
% Object create a::b
::a::b
% a public method tst args {puts [self]};
::a::tst
% a::b public method tst args {puts [self]};
::a::b::tst
% a tst
::a
% a::b tst
::a::b
%

One could add a namespace path to "::a", but
an application writer does most probably not
like to do this. One could automatically mangle
the default namespace paths (or use special
resolvers) from nx/xotcl, but that could as well
lead to surprising behavior....

Hope, this explains the observed behavior...

-gustaf neumann
PS: namespace path came already with tcl 8.5