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Re: Boxes: halfway through the comment period and no comments



On 05/17/2013 11:09 AM, John Cowan wrote:
Can I assume that means everyone on this list is entirely happy with
them exactly as written?  Ghu knows, boxes are simple, which is why
I picked them as the first R7RS-large effort.  But a little feedback
wouldn't hurt either.

They're simple, but the interactions with other concepts aren't
completely obvious.

My first question is: what is the relationship between boxes and
promises?  Is a promise a kind of box?  I.e. a promise is a box
that can only be set once?  Are they both subtypes
of something else?  Would you use a box to implement a promise?
The "auto-boxing" section clearly has parallels with similar optional
features of promises, so there a clear connections.  It's surprising
they're not actually discussed.

See this discussion of "blank promises", which is even more of
a "set-once" box:
http://www.gnu.org/software/kawa/Lazy-evaluation.html#Blank-promises

Also, what about more general types of boxes.  For example
computed boxes, which are defined in terms of getter/setter functions.
Or being able to register a callback function ("listener"), which is
called when value the in box is changed.  In some models you can
register arbitrary numbers of listeners.
--
	--Per Bothner
per@xxxxxxxxxxx   http://per.bothner.com/