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Re: Fundamental design flaws



On Thu, Oct 30, 2003 at 12:40:17PM -0800, bear wrote:
> 
> 
> On Thu, 30 Oct 2003 scgmille@xxxxxxxxxxxxxxxxxx wrote:
> 
> >On Thu, Oct 30, 2003 at 11:45:26AM -0800, bear wrote:
> 
> >> On Thu, 30 Oct 2003 scgmille@xxxxxxxxxxxxxxxxxx wrote:
> 
> >> >But they cannot be defined if they don't apply to the general class of
> >> >collections.  They need to be defined for those concrete classes or a
> >> >more specific general one (like ordered tree).
> >>
> >> Of course they can be defined for generic collections.  You can get
> >> the last element of a list; it's just the worst possible structure
> >> for that operation to be efficient.  Similarly, you can get a range
> >> of keys from an unordered alist, or any of the other "shortcut"
> >> operations.
> >
> >But what about a dictionary with no ordering at all?
> 
> In that case you just get whichever N elements are most efficient
> to get.  Or maybe you call the error continuation and make the
> user replace them with a call that makes it *explicit* that he's
> not interested in orderedness anymore -- but that's self-evident
> if he's using an unordered collection type, so it seems needlessly
> pedantic to me.

Why?  You've defined a function called get-n-from-range or what have 
you, and it does nothing of the sort.  Its even worse for other 
functions where you can't just hand out n values from anywhere.  
This is the *fundamental* flaw with having a kitchen sink of operators 
which are efficient for collections you're thinking of.

	Scott

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