Lets start with the 2 worst, irredeemable most useless, trains
C0 V1 C2 -> (u C0 v) V1 (u C2 v) fork result. duplicating input to both edge
conjunctions. Will never be used.
Alternative of (C0 V1) C2 turns this into A C train which has useful
interpretation. Avoids parentheses in one of the 2 natural (validating)
parenthesizings of this string.
C1 A2 -> u C1 (u A2) . A far less dumb alternative would be u C1 (v A2). At
least both AC and CA would be conjunctions.
I prefer (u C1 v) A2 out of consistency and coherence. While u C1 (v A2) may
have a use, its 50/50 which would be used/wanted more.
The next category is that of slightly longer combinations of A and C
(the words coherent and consistent refer to qualities that let you understand a
concept/execution train instead of memorizing incoherent and inconsistent
result tables. A highly valuable, if not priceless, aspect of a language.)
AAC not defined. bad syntax error. (AA)C is fine interpretation and already
defined sanely. AA -> (AA) is everywhere else in J.
ACA -> (u A) C (v A). Not useless, but not obviously more frequently wanted
than coherent ((u A) C v) A2
CAA -> coherent
CAC -> doesn't exist. syntax error. Can be ((u C v) A) C2. An adverb (or CA)
result.
ACC -> (u A) C1 (u C2 v) reuses u, making it useless. A perfectly coherent
result would be one equivalent to both (AC)C and A(CC). Associativity is
prizeable.
CCA -> (u C1 v) C (u A). same uselessness. (CC)A or C(CA) preferably
identical interpretations is obviously better.
CC not defined. Most important of all. -> ((u C1 v) C2) is an adverb. The
consistency with AC is that arguments are inserted with their natural
parenthesized order, and then consistent with V0 V1 C2 -> (V1 C2 V0) which
allows using conjunctions in strand/double adverb mode, which avoids the
frequent error of wishing the v argument to a conjunction referred to the full
verb phrase on the right.
First, it is more useful that definitions exist than not.
Two, definitions that reuse arguments for different modifiers have no
applicable use expectation.
Its one thing to defend the interpretations that are not useless, over a more
consistent approach. I could listen to such a defense. It's an other to
defend useless interpretations.
The next/last category are the ones that result in trains. Rather than itemize
each train, let me just go over one cool example that I can think of.
(] #~ ")
1 (= 2&|)(] #~ ")_1 i.5
1 3
its cool, except that for the " conjunction, the correct right argument is
always _1 . But there is a cooler adverb form:
(("_1) # ])
Noting that it's cool, might lose track that the purpose of the coolness is
that it can be assigned as an adverb. The power of J is in its higher order
functions that can be assigned. The alternative definition is:
select =: 1 : 'u"_1 # ]'
it is already very easy to make train results from adverbs. And an enhancement:
ns =: 2 : 'u"_1 v ]'
allows substitutes for # as v. Including i. or perhaps a compound verb that
dug through a boxed structure inside items. A super cool conjunction that was
extremely easy to write (the important value provided), and even cooler than
the train version. Cooler means harder to name.
The problem with inconsistent "non binding" of some arguments in modifier
trains is that I can write the following
(] #~ " _1) NB. parses just fine.
The intent is that if the rule of leftmost 3 parameters in a modifier train get
grouped together, and intent suggested by _1 indent, then perhaps this means
(] (#~) ")_1 NB. making an adverb out of original conjunction through binding
when it actually means:
1 (= 2&|)(] (#~ " _1)) i.5
0 0 0 0
1 0 0 0
0 0 0 0
1 1 1 0
0 0 0 0
It is a minority of J users that understand trains. Adding conjunctions and
adverbs into permissible train formation items just adds an exponential rate of
errors, and removes accessiblity even further for most J users. Sometimes the
modifiers are binding, sometimes they generate a modifier that results in a
train... increases reading taxation, that requires good memory of large
inconsistent result tables, and whether a pattern fits into one of the entries,
and loses the mental simplicity of following a train's dyadic/ambivalent terms
to understand it.
> If we change the old definitions that just means
we have even more work to do.
This can be done from the parsing table approach which may be manageable
> SHORT examples
+/ - @: -> +/ (-@:) -> -@:(+/) NB. gains strand notation for conjunctions.
Things consistently bind when you expect them to.
+ - * (@ @) -> + - (* @) @ -> + (*@-)@ -> *@-@+ NB. natural strand binding
order. Intuitively extendible to longer modifier train "saved name"
If the A V -> V A proposal is accepted then,
@ (+/) - -> -@(+/) NB. double left arguments also parse. This adds flexibility
to C C train for binding order:
* (@ @)- + -> * (@-)(@+) -> *@-@+ NB. same end result but with more partial
binding options. Can be good simplicity argument for + - left binding order
for same result.
Consistency with AC and CA means that binding any argument within the
conjunction train is easy
(@@+) -> (@(@+)), (@-@) -> ((@-)@), (*@@) -> (*@)@ are all partial bindings
that allow same end result with further conjunction or strand parameters...
when AC and CA are consistent.
part of the consistency importance is what happens when modifiers return
modifiers. Keep consuming right arguments is the "correct" behaviour. New
surprise incoherent trains are not welcome.
On Monday, September 27, 2021, 01:15:18 p.m. EDT, Henry Rich
<[email protected]> wrote:
The primary goal of reintroducing the old trains was to make the old
documents valid. Whether there is a better way to define the old trains
is not to the point. If we change the old definitions that just means
we have even more work to do.
You are not improving your credibility by asserting that 'all of the
train results... are at best marginally useful'. I used them quite a
bit and was sad to see them go. Indeed, I never had a case where I
wanted to write a modifier and found the trains wanting. I admit that I
was content with the structure of J as it is, not trying to create a
different approach to function definition.
You would have to actually demonstrate examples where an alternative
definition would enable some important new application. Then we could
judge whether the change is worth the large effort required. I would
add, we would need to do this before the beta period expires.
I have just now gone through some of your list of proposed changes and I
have yet to find one I agree with, but that's just my opinion. The
burden is on you to demonstrate the superiority of your proposal. Just
one SHORT example would be a good start, something important that the
old trains are lacking. With luck we might find that you are redefining
something so obscure that no one has ever used it, for which a change
would be easier.
In the meantime, adding parentheses to your bidents is harmless and
solves your problem.
It is gratifying to see the interest that this old code has ignited.
Henry Rich
On 9/27/2021 12:46 PM, 'Pascal Jasmin' via Programming wrote:
>> Since you can
> easily make your old code work by putting parentheses in +@/ to make
> (+@)/ and that preserves old documents, that would be the best solution.
>
> That J sometimes "does what I mean" is a mixed blessing. Great when it
> works, but relying on it means syntax errors due to its incompleteness in
> applying the intuitive concepts that could make writing modifiers easier.
>
> It all boils down to "could Ken have made a mistake"
>
> Modifier trains are an awesome idea, and it is great to have enhanced
> interpretations of code.
>
> Removing these interpretations for J6 were viewed as a better idea than these
> interpretations.
>
> The appeal of modifiers trains that return trains can seem less scary than
> modifiers that return modifiers. The latter though is part of the language
> since at least J6. Some of the "old trains" do the sane modifier
> autobinding, while others return trains.
>
> All of the train results, if not completely useless, are at best marginally
> useful. A good test would be for someone to come up with a single useful
> function in that form. Even if such a function exists, it can be
> easily/clearly written as a custom modifier in less time than it takes to
> research whether one of the train producing modifier trains provides a useful
> equivalent shortcut.
>
> CC CA AC CnvC provide tremendous benefit in having valid interpretations.
> Who wouldn't prefer more valid parsings and less syntax errors. But the
> benefit only exists when interpretations are coherent, useful, and
> consistent. That benefit only occurs if all of the modifier trains produce
> the natural modifier bindings that a fully bound in place expression would
> produce.
>
>
> That it might be scary to consider CC an adverb that produces a conjunction
> (u C1)C2 -> AC -> (uA)(Cv) or a conjunction that provides an adverb ((u C1
> v)C2) doesn't force you to use the scariness. It is consistent with the C C
> V train, and almost the V C C train. (the execution of v1 C v2 C V is (v1 C
> v2) C V, while V C C produces V C (v2 C v3)). While V C C can have useful
> applications, the "special" bracketing can be accomplished if CA had a sane
> interpretation (u C v)A. Then V C1 C2 to have current interpretation can be
> written as C2 (V C1).
>
> To Ken's credit, the dumb C A train can be avoided with C A 1 : 'u'. ie C A
> A is sane.
>
> C V C (and all duplicate u/v modifier trains) however are just mistakes and
> useless.
>
> Reintroducing these trains has great potential. But we need to fix the bad
> ones before code gets written using them, and irreparably breaks J's
> potential.
>
> It can also break complex embedded existing code. Techniques for
> strand/double adverb notation might rely on interpreter quirk, though are no
> longer needed with my proposal.
>
> + 1 : '@u/'
>
> (@+)/
>
> On Monday, September 27, 2021, 09:58:26 a.m. EDT, Henry Rich
> <[email protected]> wrote:
>
>
>
>
>
> The original parsing rules proved very useful. As you point out,
> reinstating them does change the meaning of some trains. Since you can
> easily make your old code work by putting parentheses in +@/ to make
> (+@)/ and that preserves old documents, that would be the best solution.
>
> If it would help you find what needs changing, I could type out a
> message when a modifier trident is parsed.
>
> Henry Rich
>
> On 9/27/2021 9:28 AM, 'Pascal Jasmin' via Programming wrote:
>> beta-r breaks the partial sane autoparenthesizing that existed for short
>> expressions
>>
>> in 9.02
>>
>> +@/
>>
>> (+@)/
>>
>> @+/
>>
>> (@+)/
>>
>>
>> it "breaks" when it gets too long
>>
>> @+@-
>> |syntax error
>>
>> But usually/always the intent when you write the above is (@+)(@-). The
>> syntax error is at least helpful that the parser is just incomplete in being
>> able to handle longer versions of its short parsing talent.
>>
>> with beta-r, your breaking valid sane code no one ever called a bug, and
>> replacing helpful syntax error with "mostly garbage" functional
>> interpretation
>>
>> Mostly garbage could be considered complete garbage. The case for "mostly"
>> is that some of the trains do the sane thing they should
>>
>> *(+@-@)
>> +@-@* NB. exactly sane result of autoparens.
>>
>> *(@-@+)
>>
>> *@+ - *@+ NB. complete useless garbage when you might have intended a sane
>> use but got the train rules mixed up, and in this case the parsing
>> greediness determines the sanity/insanity. (long trains group the leftmost
>> 3 terms)
>>
>> +@-@ is adverb (+@-)@ = sane
>>
>> @-@+ is (C V) ((@-@)+) where the conjunction part is a fork that is useless
>> because of duplicate arguments to the (C0 V1 C2) train.
>>
>>
>> beta-r is harmful because:
>>
>> 1. it breaks existing valid code.
>> 2. produces worse expressions than a syntax error.
>> 3. prevents the natural and useful enhancement of J's parsing by
>> interpreting garbage of no practical use.
>> 4. Modifier trains are an extremely useful addition to J, but only if they
>> have useful interpretations.
>>
>> (C V C) conj -> (u C V C v) ie. interpreted the same way as if terms had
>> been written inline is intuitive and powerful partial function enhancement
>>
>> .
>>
>> On Monday, September 27, 2021, 02:29:30 a.m. EDT, Raul Miller
>> <[email protected]> wrote:
>>
>>
>>
>>
>>
>> Parenthesization is basically talking about how the parser itself
>> functions. Every point where the parser combines tokens is a point
>> where you could place a parenthesis pair in the original text without
>> significantly altering the parsed meaning of that text.
>>
>> So proposals involving changing the parenthesis rules are proposals to
>> replace the parser itself.
>>
>> But changing the parser would invalidate quite a bit of existing
>> documentation on J, which would place a severe burden on the J
>> community.
>>
>> Take care,
>>
>>
>> --
>> Raul
>>
>> On Mon, Sep 27, 2021 at 12:42 AM 'Pascal Jasmin' via Programming
>> <[email protected]> wrote:
>>>> When you envision 'even longer modifier trains', you are implicitly
>>> requiring a stack of more than 4 words.
>>>
>>> which can be avoided by (auto)parenthesizing outer modifier train, such
>>> that there's always at most 4 tokens.
>>>
>>>
>>> Do I understand the following expression to mean that modifier trains group
>>> left to right (somehow)?
>>>
>>> @ @ + - @
>>>
>>> (@ @ +) - @
>>>
>>>
>>> @ @ + - @ /
>>>
>>> ((@ @ +) - @)/
>>>
>>>
>>>
>>> / @ @ + - @
>>>
>>> |syntax error
>>>
>>> | /@@ +-@
>>>
>>>
>>> / (@ @ + - @)
>>>
>>> /((@ @ +) - @)
>>>
>>>
>>> @ + @ - @
>>>
>>> (@ + @) - @
>>>
>>> shouldn't it group from the right?
>>>
>>>
>>> On Sunday, September 26, 2021, 10:46:13 p.m. EDT, Henry Rich
>>> <[email protected]> wrote:
>>>
>>>
>>>
>>>
>>>
>>> Since the goal was to make the old documents still usable, changes would
>>> require strong arguments demonstrating their superiority. You are
>>> pitting yourself against Ken Iverson: may the better man win.
>>>
>>> I can assure you that whatever is in your 'templating system' had zero
>>> influence on the design and implementation of {{ }} .
>>>
>>> When you envision 'even longer modifier trains', you are implicitly
>>> requiring a stack of more than 4 words.
>>>
>>> Henry Rich
>>>
>>> On 9/26/2021 10:34 PM, 'Pascal Jasmin' via Programming wrote:
>>>> I've been working on an autoparenthesizing of modifier trains, with
>>>> interpretations that would seem much more useful than the "old stuff". I
>>>> don't have a good interpretation for A V train, so I guess it could stay
>>>> as suggested. The following are what I'd prefer, added after -> ( = means
>>>> equivalent)
>>>>
>>>>
>>>> V0 V1 C2 conj V0 V1 (u C2 v) -> V0 (V1 C2) = V1 C2 V0
>>>> A0 V1 V2 adv (u A0) V1 V2
>>>> C0 V1 V2 conj (u C0 v) V1 V2 -> (C0 V1) V2 = A V2
>>>> C0 V1 C2 conj (u C0 v) V1 (u C2 v) -> u (C0 V1) (C2 v)
>>>> A0 A1 V2 conj (u A0) (v A1) V2 -> (u A1 A2) V2
>>>> N0 C1 A2 adv N0 C1 (u A2) -> u (N0 C1) A2
>>>> N0 C1 C2 conj N0 C1 (u C2 v) -> u (N0 C1) (C2 v) = ((N0 C1 u) C2 v)
>>>> = (v (u (N0 C1)) C2) parentheses not needed.
>>>> V0 C1 A2 adv V0 C1 (u A2) -> u (V0 C1) A2
>>>> V0 C1 C2 conj V0 C1 (u C2 v) -> same as N C C
>>>> A0 C1 N2 adv (u A0) C1 N2
>>>> A0 C1 V2 adv (u A0) C1 V2
>>>> A0 C1 A2 conj (u A0) C1 (v A2) -> u A0 (C1 v) A2
>>>> A0 C1 C2 conj (u A0) C1 (u C2 v) -> ((u (A0) (C1 v)) C2) = adverb
>>>> C0 C1 N2 conj (u C0 v) C1 N2 -> v (u C0)(C1 N2) = (u C0 v)(C1 N2)
>>>> C0 C1 V2 conj (u C0 v) C1 V2 -> same as above
>>>> C0 C1 A2 conj (u C0 v) C1 (v A2) -> ((u C0 v) C1) A2 = adverb
>>>> C0 C1 C2 conj (u C0 v) C1 (u C2 v) -> ((u C0 v) C1) C2 = conjunction
>>>> A C
>>>> A0 C1 adv (u A0) C1 u (adverbial hook) -> (u A0) C1 v
>>>>
>>>> The beauty of the suggested forms is that there is not much to remember,
>>>> and allows for parenthesless forms.
>>>>
>>>> V0 V1 C2 -> V0 (V1 C2) is just the only valid parenthesization of the left
>>>> expression.
>>>>
>>>> C0 vn C2... More modifiers -> (C0 vn) C2...M ie. when a nv term is between
>>>> 2 conjunctions it binds to the left one.
>>>>
>>>> Whenever C vn appears, (C vn) is bound is the only special rule. It binds
>>>> ahead of other modifiers to right.
>>>>
>>>> To permit even longer modifier trains, while keeping the 4 token stack:
>>>>
>>>> C0 C1 M2 M3 -> C0 C1 (M2 M3)
>>>>
>>>> Reusing parameters in multiple modifiers seems stranger than the still
>>>> strange inserting them seemingly arbitrarily within a modifier train. If
>>>> these are useful, they are best made into a purpose modifier rather than
>>>> as default parsing rules that will confuse.
>>>>
>>>> A cool enhancement would be multiple right bindings to modifier trains
>>>> that contain multiple conjunctions:
>>>>
>>>> (C0 C1 M) v -> (C0 v) C1 M ie. A conjunction modifier train binds v to the
>>>> leftmost (unbound) conjunction.
>>>> ((C0 v) C1 M) v2 -> (C0 v) (C1 v2) M = (C0 C1 M) v v2
>>>> u ((C0 v) C1 M) -> ((u C0 v) C1) M ie binding from left or right provides
>>>> options similar to "old stuff"
>>>>
>>>> templating system that may have formed basis for {{ }}, and allows for
>>>> rich custome modifier trains:
>>>> http://www.jsoftware.com/pipermail/programming/2020-September/056558.html
>>>>
>>>>
>>>> On Sunday, September 26, 2021, 12:01:45 p.m. EDT, Henry Rich
>>>> <[email protected]> wrote:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Nostalgic old-timers will be happy to see the return of Modifier Trains,
>>>> such as (@/), which were in early J but were deleted long ago. See
>>>> https://code.jsoftware.com/wiki/Vocabulary/fork#invisiblemodifiers .
>>>>
>>>> These trains were one of Ken Iverson's elegant brilliancies. Few used
>>>> them, and they are not needed, because anything they do can also be done
>>>> with explicit modifiers ({{ u @ v/ }} is equivalent to (@/)). No one
>>>> need rush out and look at them.
>>>>
>>>> We have brought them back because to do so was easier than updating all
>>>> the old J literature that refers to the forms. And because they're cool.
>>>>
>>>> Henry Rich
>>>>
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