Changing } to a conjunction would break just about every J codebase in
existence, so I can't jump on that bandwagon.
Moving item amend to }:: would conflict with the interpretation of LHAs to {::
, which }:: will and should share when it is available (ie the obstacles to
implementation are worked out [Roger, what are those?]). Since I see native
tree-processing as an important progression of the J language, I can't see my
way to this suggestion either.
Of course, we could "move" item amend somewhere else, but at that point I'd
rather just have it in user space (the standard library, so everyone would
still at least have access to that).
But before we get there, I'd still like to see a better candidate for the
interpretation of the monadic verb m} with a comparison of benefits and
drawbacks, or a really strong argument for why m}y should be changed to an
error. Any change at all (redefinition or "de"-definition) would have to be
worth breaking backwards compatibility - especially with my code! :)
-Dan
> On Mar 30, 2014, at 5:46 PM, Pascal Jasmin <[email protected]> wrote:
>
> I realize there would be a loss in flexibility from changing the v0`v1`v2 }
> form, and so good reason to keep it.
>
> For item amend, putting it on }:: would place it "out of the way". With it
> out of the way, } can make more sense as a conjunction than an adverb, and
> not have the decision clouded with Item amend using the same symbol.
>
> A natural definition for monad } would be "item delete" ie. amend with fill
> if a full item is not amended, or otherwise remove if a full item.
>
>
> My definition for the amend conjunction is extremely useful, and might form a
> better 2 gerund version of }
>
> so +:` 1: } i. 3 3 would be the same as my amend conjunction
>
> +: amend 1 i. 3 3
>
> It would apply to both monad and dyad } the definition again:
>
> amend_z_ =: 2 : 0
> s=. v"_ y
> (u"_ (s{y)) (s}) y
> :
> s=. v"_ y
> (x u"_ (s{y)) (s}) y
> )
>
>
>
>
> The proposal to completely replace } with my amend conjunction instead of an
> adverb, could work. Its still possible to apply ranked } as:
>
> 5 (0)}"1 i. 3 3
> 5 1 2
> 5 4 5
> 5 7 8
>
> 5 amend 0"1 i. 3 3
> 5 1 2
> 5 4 5
> 5 7 8
>
>
> The existing 2 gerund } seems pretty useless (minimal benefit from x v2 y not
> repeating x to the right of }... Not much expectation that the same x would
> be useful to v2 as it is to v0,v1). Though a gerund version of the amend
> conjunction would be a bit harder to use (than conjunction) if there were a
> performance benefit from being built in, it might still be.
>
>
> ----- Original Message -----
> From: Dan Bron <[email protected]>
> To: "[email protected]" <[email protected]>
> Cc:
> Sent: Sunday, March 30, 2014 3:28:58 PM
> Subject: Re: [Jprogramming] Item amend ~: index error.
>
> Pascal wrote:
>> There is no good reason for item amend to be an adverb.
>
> Except that } , is an adverb (and there's a very good reason for that: to use
> it for "regular amend" requires 3 distinct arguments, and verbs can't have
> more than 2). That is, there's no way for the } in x } y to be a verb and yet
> still have x idx} y work (because that requires } to be an adverb, not a
> verb. The same symbol can't be an adverb sometimes and a verb other times).
>
> If you're instead saying that there's no reason for J to offer the
> functionality of "item amend", or anyway it shouldn't be advertised in such a
> prominent location as
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