Re: [Jprogramming] Closures; WAS: Verbs returning verbs

[Elijah Stone]

(To be clear, closures are orthogonal, from a language perspective, to 
syntactically first-class functions.  But they often appear together, and I 
think the former more important, which is why I took the opportunity to bring 
it up.)

On Tue, 17 Jan 2023, Henry Rich wrote:
I don't follow any of this thread, because I don't understand what is 
missing from standard J.  I find J adequate for everything I want to 
do.  What am I missing?

I can see that if you want to write all-tacit code you have trouble if 
you need to feed a verb result into a modifier.

Suppose though that I am content with writing explicit definitions.  
What do I need beyond the standard language, and for what use case?

Henry Rich

On 1/17/2023 9:23 PM, Elijah Stone wrote:
(Curried modifiers, as you say, are a solution, but, again, another 
half-solution.)

On Tue, 17 Jan 2023, Raul Miller wrote:

Here, I suspect that you're only getting noun values in your closure
-- you'll have to sprinkle those noun references with something like
`:6 if you want anything else. That's probably not a huge problem.

But, thinking about this, personally I'm not seeing a lot of
motivation for this approach, either. (What problems would this solve?
I'm sure there are some great motivating examples out there. And
closures certainly have a lot of popularity. But... position in a list
can be thought of as being conceptually analogous to a variable, so it
should be apparent that we already have some support for the
algorithmic role of closures.)

(I should perhaps also note, here, that conjunctions and adverbs which
have verb results are self-currying.)

Anyways... I'm not thinking particularly deep thoughts here -- I'm
just reflexively reaching for motivating examples (which might assist
in forming some of those sorts of thoughts).

Thanks,

--
Raul


On Tue, Jan 17, 2023 at 7:01 PM Elijah Stone <elro...@elronnd.net> 
wrote:

I suggest:

[x] u &:: (k;v;k;v...) y

Will evaluate u with bindings kvkv... (raveled) active. Should work 
for both
explicit and tacit.  Implementation is allowed to coalesce; e.g., u 
&:: (k;v)
&:: (k;v) `'' may be rendered u &:: (k;v;k;v), deduplicated, &c.
Substitution also ok; eg (f%#) &:: ('f';+/`'') becomes +/%#.

I would like for verbs defined inside of explicit verbs to be 
implicitly
closed; this is obviously a compat break, but.

On Tue, 17 Jan 2023, Elijah Stone wrote:

> I don't love the proposal, as I think a conception of verbs as 
first class
> should involve _less_ hackery with representations, not more.  But 
I don't
> feel that strongly either way.
>
> More fruitful, IMO, would be to work out how to add closures, as I 
think
> there
> is a more urgent need for that (u./v. is a band-aid). Perhaps taking
> inspiration from kernel (but skipping the mutation!).
>
> On Mon, 16 Jan 2023, Henry Rich wrote:
>
>> I have never understood the zeal for having verbs return verbs, 
but it
>> must be real if some are willing to use dangerous backdoor hacks 
into JE
>> to achieve it.  ARs make it possible to pass verbs around, but 
executing
>> them requires dropping into explicit code.  To remedy this, I 
offer a
>> proposal, backward compatible with older J:
>>
>> 1. (". y) and Apply (x 128!:2 y) to be modified so that if the 
result of
>> execution is not a noun, it is replaced by its AR (instead of '' as
>> previously).
>>
>> 2. (". y) and Apply to be modified so that if y (for ".) or x (for
>> Apply) is boxed, the sentence is executed as usual except that 
each box
>> is converted using (box 5!:0) before being put onto the execution 
stack.
>>
>> The idea is that you can execute (".
>> expr-producing-AR,exp-producing-AR,...) without having to get any
>> modifiers involved.
>>
>> Sentence execution can produce ARs, and can take ARs created by 
verbs to
>> represent verbs and modifiers.  That sounds pretty classy to me, 
but I
>> don't know whether it's first-class.
>>
>> Henry Rich
>>
>>
>>
>> 
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