[om] semantics of structure sharing

[jhd at cs.bath.ac.uk]

On Thu, 11 Apr 2002, Richard Fateman wrote:
> I don't understand this OMA(choice... ) business, but frankly
> any time an OM utterance evaluates ANYTHING, it seems to me
> to be overstepping its bounds.
No - it's merely overstepping the bounds of what OM per se prescribes. 
Many OM systems will evaluate, but may attach different meanings to this 
evaluation. 
> Somehow requiring OM to evaluate random()  more than once
> goes much further.
> 
> OM can presumably convey two messages from point A to point B.
> in lisp...
> 
> (f (+ (random 10)(random 10))
> 
> 
> or
>    ((lambda(x)(f (+ x x))) (random 10))
> 
Agreed.
> It cannot in either case say what (random 10) means.  only
> the recipient can do that.
It can say something (though might well not in the case of random!) about 
what it means (as opposed to what the recipient does with it!).
> And frankly, the recipient can evaluate these in any of several
> ways, including a way that maps the second utterance to the
> first, probably doing an injustice to the system uttering
> the lambda.   (But ONLY in the case that random is not a function.
> If random is a function, the Church-Rosser theorem says they
> are equivalent if they both terminate.)
I would argue that this is non-compliance, since the OM clearly stated 
that there was onlyone use of random.
> Perhaps it would help if OM people were more conversant with
> functional programming.  Apologies for repeating myself..
Quite a few of us do, Richard.
James
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