[Omake] allowing for lazy extends?

[Erick Tryzelaar]

Aleksey Nogin wrote:
>> Without it, I run into all sorts of issues because "extends" forces 
>> evaluation, even if it's a lazy variable. So I have to do all sorts 
>> of hacks in order to avoid extending things until the last possible 
>> moment.
>
> Note that you can implement lazy extension yourself:

Thanks for that! That does exactly what I want. I did notice that it 
does add some extra things (name, var, val) to my object, which I'm not 
sure is on purpose:

% EXECUTABLE +=
EXECUTAB> EXECUTABLE +=
EXECUTAB>    .
.
- : class Object
       object-length = <fun 0>
       object-map = <fun 1>
       object-mem = <fun 1>
       com = <fun 2>
       exe = <sequence> : Sequence
       flags = <sequence> : Sequence
       make-rule = <fun 2>
       object-find = <fun 1>
       object-add = <fun 2>
       comflags = <fun 2>
       object-foreach = <fun 3>
% C. =
C>        C. =
C>           lazy_extend(C)
C>           .
.
- : class Object
       object-length = <fun 0>
       object-map = <fun 1>
       object-mem = <fun 1>
       com = $(apply global.obj-find $(apply global.getvar "C" : 
Sequence) "com" : Sequence)
       name = $(apply global.obj-find $(apply global.getvar "C" : 
Sequence) "name" : Sequence)
       exe = $(apply global.obj-find
                $(apply global.getvar $(apply global.obj-find $(apply 
global.getvar "C" : Sequence) "name" : Sequence))
                "exe" : Sequence)
       flags = $(apply global.obj-find
                  $(apply global.getvar $(apply global.obj-find $(apply 
global.getvar "C" : Sequence) "name" : Sequence))
                  "flags" : Sequence)
       make-rule = $(apply global.obj-find
                      $(apply global.getvar $(apply global.obj-find 
$(apply global.getvar "C" : Sequence) "name" : Sequence))
                      "make-rule" : Sequence)
       object-find = <fun 1>
       val = <fun 3>
       var = "object-foreach" : Sequence
       object-add = <fun 2>
       comflags = $(apply global.obj-find
                     $(apply global.getvar $(apply global.obj-find 
$(apply global.getvar "C" : Sequence) "name" : Sequence))
                     "comflags" : Sequence)
       object-foreach = <fun 3>


> P.S. On one hand, I would prefer not to make any significant semantic 
> changes in 0.9.8 - finishing the work on scalable variable scoping and 
> reuniting the two branches has priority.
>
> On the other hand, we do need to take a systematic look at how the 
> laziness is implemented and probably come up with a more flexible and 
> consistent approach - see the discussion at 
> http://bugzilla.metaprl.org/show_bug.cgi?id=628

I'm fine with using this for now. It'll be nice to have this integrated, 
but now it's no longer a showstopper :)

-e