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Postings from December 2008
On 2008-Dec-6, at 7:37 am, Aristotle Pagaltzis wrote:
> Funnily enough, I think you’re onto something here that you didn’t
> even notice: [...]
> if we had a NOTFIRST (which would run before ENTER just as FIRST
> does, but on *every* iteration *except* the first), then we could
> trivially attain the correct semantics and achieve all desired
> results:
>
> repeat {
> @stuff = grep { !.valid }, @stuff };
> NOTFIRST {
> .do_something( ++$i ) for @stuff;
> }
> } while @stuff;
>
> The really nice thing about this is that the blocks are nested, so
> that any variable in scope for the invariant enforcement will also
> be in scope in the NOTFIRST block without the user ever having to
> arrange another enclosing scope.
Oh, yes! So what if we had "LOOP $n {}" that executed on the nth
iteration? "LOOP 0 {}" at the beginning would be like FIRST {}, "LOOP
* {}" at the end would be like LAST {}, and "LOOP 1..* {}" would give
us the NOTFIRST block. Presumably you could have multiple LOOP blocks
too.
(Actually, you couldn't quite do FIRST/LAST using LOOP $n, because
FIRST/LAST occur outside ENTER/LEAVE, whereas LOOP would occur
inside. But perhaps you could have LOOP blocks inside ENTER/LEAVE
blocks?)
-David
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