Sorry for not responding earlier, but I think your ``each2*`` is just:
``[ ] swap map-reduce``
On Wed, Jan 18, 2017 at 10:20 AM, Alexander Ilin <ajs...@yandex.ru> wrote:
> Hello!
>
> I've got a task where I need to process a sequence of elements pairwise,
> while collecting the (possibly mutated) elements into a new sequence.
>
> The neighboring elements may affect each other, hence the need for
> mutation.
>
> I searched through the help system looking for words similar to
> each-pair or each2, to no avail.
>
> Here's what I came up with:
>
> ```
> :: each2* ( seq quot: ( prev next -- next' ) -- )
> seq unclip-slice :> elt! quot '[ elt @ elt! ] each ; inline
> ```
>
> What I want to happen is this:
>
> ```
> { 1 2 3 } [ [ swap . . nl ] keep 10 + ] each2*
> 1
> 2
>
> 12
> 3
> ```
>
> So that the quotation passed to `each2*` would walk through all
> consecutive pairs of the elements in `seq`, but would also be able to
> mutate the `next` element for its next iteration.
>
> Now, I have no experience with functional languages (in fact, that's why
> I'm studying Factor, so feel free to correct me), but my suspicion is that
> I inadvertently created a closure over the `elt` variable, because instead
> of the expected output I get the following:
>
> ```
> { 1 2 3 } [ [ swap . . nl ] keep 10 + ] each2*
> 1
> 2
>
> 1
> 3
> ```
>
> By using the walker I see that the initial value of `elt` is curried to
> the quotation, so the subsequent `elt!` has no effect.
>
> Please, tell me: is this the intended interaction between the locals and
> the fry, or is it an optimization gone wrong?
>
> And how do I get the behavior that I want from the `each2*`? Is there a
> totally different approach that I missed? My intention is to use `each2*`
> inside the `make` call to construct the result I need.
>
> Thank you!
>
> ---=====---
> Александр
>
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