Hi,

Can you give an example where this ordering would be useful?

Ivan 




> -----Original Message-----
> From: Richard A. O'Keefe [mailto:ok at cs.otago.ac.nz]
> Sent: Wednesday, March 13, 2002 8:03 PM
> To: squeak-dev at lists.squeakfoundation.org
> Subject: Re: A suggestion
> 
> 
> "Lex Spoon" <lex at cc.gatech.edu> wrote:
> 	> (There are other orders which are also compatible 
> with =, such as
> 	>  - first compare the lengths,
> 	>  - then compare the elements ONLY if the lengths are the same.
> 	>  This is almost always faster, and has some nice properties.
> 	
> 	Gee, yet another way to compare collections.  Note, 
> though, that this is
> 	not a total ordering, either -- arrays of different 
> lengths will be ~=
> 	but they will be neither #< nor #> .
> 	
> No, it's a total order.
> 	#(4) < #(1 2)		(length is less)
> 	#(1 2) < #(4 2)		(length =, first element <)
> 	#(1 2) < #(1 4)		(length =, last element <)
> 
> If two arrays have different lengths, then one of them is shorter,
> and that one is less.  If they have the same length, then either
> all elements are equal, so the arrays count as equal,
> or one position has unequal elements, and the first such position
> determines the order.  (Of course, taking the last position would
> also work.)
> 
> This order was used on strings in PL/CV,
> and it's _almost_ the order Prolog uses.
> (Prolog actually compares function symbols first, then arity,
>  and then elements.  So if you use f, f(X1), f(X1,X2), .. and so
>  on for sequences, you get this order.)
> 
> I'm not advocating that ordering; lexicographic has always suited me.
> I brought it up because that's the reason why I didn't just post an
> [ENH].
>