[xquery-talk] How much laziness is permitted?

Florent Georges lists at fgeorges.org
Wed Mar 11 17:34:39 PST 2009

John Snelson wrote:


> As it turns out, try/catch is actually a blocking operation
> on lazy evaluation. If a lazily evaluated expression inside
> a try/catch block returns (1, 2, 3) but then raises an
> error, the implementation effectively needs to
> "recall" the values (1, 2, 3) and instead return
> the value of the catch expression. Since most lazy
> implementations won't have the ability to
> "recall" values already returned, this means they
> can't return any values until expression evaluation has
> terminated - in other words, they need to evaluate eagerly.

  I have some difficulties understanding the problem.  Could you provide me with a little sample or pseudo code showing such a situation?


Florent Georges


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