[closer-devel] LAYER-NAME vs LAYER in ADJOIN-LAYER/REMOVE-LAYER.

[Pascal Costanza]

Hi there,

Sorry for the late reply, we're pretty busy around here with some last  
project proposal writing before the summer holidays.

I understand your concern, and the suggested fix certainly makes it  
work. However, it's not so nice, because this will needlessly  
increases the cache sizes, because every named layer may end up twice  
in the caches, once based on the names, and once based on the  
metaobjects.

I see two ways out: Either I use the metaobjects everywhere, and use  
the names only for the user-level macros (which expand into code that  
converts the names into metaobjects as soon as possible.

Or I make sure that anonymous layers have unique names as well: At the  
moment, their names are 'nil, but I could use the metaobjects  
themselves as 'names'. (For example, (layer-name #<STANDARD-LAYER- 
CLASS NIL 21ECFE23>) => #<STANDARD-LAYER-CLASS NIL 21ECFE23>.

The first option may conceptually be cleaner, but requires more work  
and may potentially break some existing code (not sure about the last  
point, but my gut feeling tells me that there are some potentially  
problematic corner cases waiting for me if I go down that path).

The second option is relatively easy to do. It may still require a  
couple of changes here and there, but I don't expect any serious  
problems. Somehow, I prefer that you can use the layer names in the  
functional API (adjoin-layer, remove-layer, ensure-active-layer, and  
friends).

Does anybody have any strong opinions about this?

Anyway, thanks a lot for raising this issue, I wouldn't have noticed  
that problem otherwise. The ContextL MOP is the least polished part of  
ContextL, so such feedback is especially useful. May I ask what you  
are actually using this for? (I like abuses of language constructs,  
this usually gives hints for new ideas for missing features...)

Best,
Pascal

On 24 Jun 2009, at 18:06, Drew Crampsie wrote:

> Hello,
>
> I'm sure i'm abusing contextl in some way (anonymous layers that
> themselves are layered classes), but for my code to work the call to
> ADJOIN-LAYER in REMOVE-LAYER-USING-CLASS must pass the layer directly
> to ADJOIN-LAYER, not indirect through the layer name.
>
> In other words :
>
> hunk ./cx-layer.lisp 103
> -                                (layer-name active-layer)
> +                                active-layer
>
> This works for me and passes all the tests, but i'm not sure if it's
> the right thing to do... i'm likely abusing contextl in many ways ;).
>
> Cheers,
>
> drewc
>
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-- 
Pascal Costanza, mailto:pc at p-cos.net, http://p-cos.net
Vrije Universiteit Brussel
Software Languages Lab
Pleinlaan 2, B-1050 Brussel, Belgium