On 12 Aug 2014, at 08:29 , Simon Knapp <sleepingwell at gmail.com> wrote:
> Hi List,
>
> Is it possible to define how 'in' works for an object of a specific
class
> (to achieve a similar result to implementing the iterator protocol in a
> class Python)?
>
No, because 'in' doesn't really exist, it is "syntactic
sugar" to sweeten a call to the "for" function with its three
arguments. E.g.
> `for`(i,1:2,print(i))
[1] 1
[1] 2
So what you're really asking for is something like a `for` with class
dispatch or the two first arguments replaced by an iterator mechanism.
That's not in the cards, at least at the moment, but I suppose it isn't
completely out of the question either -- ideas of this sort get bandied around
occasionally. It would require changes to R's internals; it is not something
you can do in (say) a package.
> Cheers,
> Simon Knapp
>
> [[alternative HTML version deleted]]
>
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Peter Dalgaard, Professor,
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