[xquery-talk] Fold-right

W.S. Hager wshager at gmail.com
Thu Jan 12 09:10:14 PST 2017

Can we please agree to add a footnote to the fold-right example that says
something along the lines of "this example algorithm may be optimized using
lazy evaluation in the interpreter"? I don't see how that is biasing the
spec toward a specific implementation...

2017-01-12 17:27 GMT+01:00 Michael Kay <mike at saxonica.com>:

> >
> > Agreed, but that wasn't my point. You may have the opinion that it
> wasn't important, but I'm curious to know where anything tangible on
> laziness is mentioned.
> It isn't - deliberately. We leave "quality of implementation" issues
> entirely to the implementor. There are many implementation techniques
> available, including ones that may not have been invented yet, and there
> are different trade-offs between time and memory, and the spec quite
> deliberately doesn't get involved in such matters. The spec tells you what
> result to expect, it doesn't tell you when to expect it.
> Michael Kay
> Saxonica
> > As you say, not having any won't be very efficient, so you may as well
> be explicit about it, right? I don't really understand why it's preferable
> to have a syntax without an implementation, and I simply pointed out that
> in the case of the fold-right example that becomes slightly odd...


W.S. Hager
Lagua Web Solutions
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