Re: [TCLCORE] Tcl Objects with value semantics

[Duquette, W. H (393K) <wil...@jp...>]

--
Will Duquette -- Wil...@jp...
Athena Development Lead -- Jet Propulsion Laboratory
"It's amazing what you can do with the right tools."





On 7/28/15 7:07 AM, "Donal K. Fellows" <don...@ma...>
wrote:

>On 28/07/2015 13:28, Cyan Ogilvie wrote:
>> I've used a variant on this approach for about 10 years and it's stood
>> up well in production environments, but something closer to actual value
>> semantics would be nice.  I've thought about implementing a custom
>> Tcl_Obj type, but that really feels like abuse, and it's tricky to
>> define a string rep that is efficient.
>
>I've been thinking about doing a garbage-collection scheme for TclOO, to
>be only turned on for objects created with the 'new' method. (I suppose
>it could even be put in a metaclass, so that existing objects wouldn't
>have the problem.) The idea would be to track when there cease to be any
>Tcl_Obj references to the object, and delete it when they're gone.
>Formally not great ‹ it's not how any ³proper² current value semantics
>work, though it is close to what JTcl and tcom do ‹ but would work in
>practice (and would support the ³use as a value² style quite naturally).

This would scratch part of my itch pretty well: it would be possible to
return objects with methods from a proc and not worry about having to
dispose of them.

Will

>
>Doing it would require some small core changes in the main command
>dispatch, as that currently forces values to be of a particular
>Tcl_ObjType that doesn't (so far as I know) support useful deletion
>callback semantics. Otherwise it would be pretty much self-contained.
>
>Alternatively, TOOT <URL:http://wiki.tcl.tk/11543> by Neil Madden.
>
>Donal.
>
>
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