Re: [Xotcl] xotcl namespace auto-import

From: Gustaf Neumann <neumann_at_wu-wien.ac.at>
Date: Tue, 25 May 2004 10:43:07 +0200

On Monday 24 May 2004 22:57, Neil Madden wrote:
> Hello all,
>
> Small feature request: could XOTcl be made to automatically [namespace
> import] the ::xotcl::* commands into every object it creates?
> ...
> 1) Fully qualify everything - lots of xotcl::my, xotcl::self etc
> everywhere
> 2) Import xotcl namespace manually into each object namespace.
>

 or 3) do a gobal namespace import.

> 2 is better than 1, but is still a bit of a pain to remember to do, and
> I seem to remember trying it and it not always working (I could be
> wrong about that).

 (2) does not help too much, since xotcl is "namespace transparent",
 which means that it simply keeps the current namespace.
 This means that if you do a "namespace eval xxx {o m}"
 the method is evaled in the namespace xxx (and not o}.

 As a sidenote: not every xotcl obj creates a namespace, since
 tcl namspaces are quite large in memory. Namespaces are
 only created when an object has child objects or procs. You
 can measure the difference on your system (the following works
 for linux, ps might be different on other OSes)

==============================================
::xotcl::Class Mem -instproc init {} {
  set r [exec ps -xv | fgrep [pid]]
  ::xotcl::my set m [lindex $r 6]
}

set n 1000
Mem m1

set ts [time {for {set i 0} {$i<$n} {incr i} {
  ::xotcl::Object create a$i}}]
Mem m2
set mem1 [expr {([m2 set m]-[m1 set m])*1024/$n}]

set ts [time {for {set i 0} {$i<$n} {incr i} {
  ::xotcl::Object create b$i -requireNamespace}}]
Mem m3
set mem2 [expr {([m3 set m]-[m2 set m])*1024/$n}]

puts "consumption/obj without ns: $mem1, with ns: $mem2"
==============================================

> So, my feature request would be that all Objects [namespace import] the
> xotcl namespace automatically.[1]

 we had something like this in earlier versions of xotcl, but it was quite
 a pain, where it was quite easy to run into inifine loops, since
 procs of objects were resolved without the object name. To be on
 the safe side, every reference to a gobal tcl command had to be
 prefixed by a :: (eg: ::set x 1), otherwise an "obj proc set .."
 was overruling the tcl command. Note that we have multiple
 command sets in xotcl, not only in the procs, but in the instprocs
 of classes (superclasses, mixins) as well.

 you can do the following as other alternatives:
 a) you can import the xotcl commands into your
     components workspace, and do a namespace eval
     there
 b) you can eval the object in the ::xotcl namespace
 
 here are such code snipplets:
==================================
namespace eval myns {
  namespace import ::xotcl::*

  Class MyClass
  MyClass instproc test {} {
    puts stderr "in [xotcl::self] current namespace [namespace current]"
    puts "unprefixed: [self] [self class]"
  }
  MyClass o

}

puts =========
namespace eval myns { o test }

puts =========
namespace eval xotcl {myns::o test}
puts =========

==================================

 if you have a component with a slim interface, you can
 simply do a namespace eval once on the top calling level, this
 does not cost much performance.

 ... and, you can write a global unknown handler, but that is not
 better than importing xotcl (or at least self+my) globally, what
 still looks like the best option to me.

-gustaf

-- 
Univ.Prof. Dr.Gustaf Neumann
Abteilung für Wirtschaftsinformatik
WU-Wien, Augasse 2-6, 1090 Wien