J has gotten some powerful tools in 903 for making compound modifiers
(modifiers that return other modifiers) and some interesting parentheses
eliminations
The following 6 modifiers create forks. The 3 Fm ones are adverbs that return
conjunction when n indicates the fork tine that is fixed by the adverb. The
Fmn ones are conjunctions that fix positions m and n to return an adverb that
will fill the remaining position.
cocurrent 'z'
F0 =: 1 : 'u ` ` `: 6'
F1 =: 1 : '[. u ].'
F2 =: 1 : '` ` u `: 6'
F01 =: ((` (2 : '`')))(`:6)
F02 =: 2 : '(u`)(`v)(`:6)'
F02 =: ( ([.(2 : '`')) (2 : '`' ].) ) (`:6)
F12 =: (2 : '`' `) `: 6
The conjunction forms can all be made tacit other than the (2 :'`') bits that are used to
"fool" CC trains into forming adverbs. I withdraw my criticism of CC, because
the trick of 2 :'C' in place of a conjunction is a very flexible short and readable way
of making CC (and other modifier trains) return compound modifiers.
The facit version of F02 is ((CC)(CC))A -> CA -> (AA)A
F1 and F12, and F0 and F02 have same binding order with 3 parameters. (and F2
would match a swapped F12, named F21 but not provided above)
These compound modifiers reduce parentheses use, while permitting more flexible
composition.
In terms of choosing an F shadow name, F1 or F12 seem like the best choices,
because they both keep the same fork order.
+/ %F1 #
+/ % #
F1 has the advantage of binding any single adjacent parameter while keeping
order of remaining parameters, and can also do this:
#(+/ %F1)
+/ % #
+/ % (F1 #) NB. A V form
F12 has less binding flexibility, but because it is an "original" conjunction,
it binds its right parameter, and so the whole fork becomes a parameter to any other
modifiers
+/ % F12 # "1
(+/ % #)"1
+/ % F1 # "1
+/ % #"1 NB. since F1 is adverb, w u F1 v (AA)CvAAAA -> w (u F1) ((((v (AA)Cv)A)A)A)A).
ie. v will bind with expression to its right "normally" as if it were a u parameter.
F =: F12 NB. instead of F =: F1 is chosen for composability, saving 2 chars
instead of 1. F1 still very useful.
compositions with F1 can choose which adverbs/modifiers operate on the v
parameter and which operate on full fork
+/ % (F1 (<.@:)) #"1
<.@:(+/ % #"1)
#"1(+/ % F1) (<.@:)
<.@:(+/ % #"1)
#(+/ % F1) (<.@:)"1
<.@:(+/ % #)"1
+/ % F # (<.@) = F] # F] (#@) NB. count of items that are equal to floor of
average
#@((<.@(+/ % #) = ]) # ]) NB. much easier to type out/read. Parenthesized
expressions are short
] +/ %(<.@) F # = F] (F2 (#@)) #~ NB. same expression but swapped term
positions, and adverb move
#@(] #~ (+/ <.@% #) = ])#@(] #~ <.@(+/ % #) = ]) NB. minimal edit effort.
A guideline for which of the 6 fork generators to use is to leave the most
complicated term of the fork as the leftmost parameter. Though there is much
more flexibility than in previous J versions
] = F1 +/ % F # NB. using F1 allows for "complicated" right part
] +/ % F # (F2"1) = NB. complex part in u (of F2)
(] = +/ % #)"1
] +/ % F # F01 = "1 NB. similar but may have reading preference. (F01"1) also
legal
((+/ % #) = ])"1
On Tuesday, December 14, 2021, 12:53:38 p.m. EST, 'Pascal Jasmin' via Programming
<[email protected]> wrote:
Making an ammend conjunction patterned around the u`v`]} form but where u is a
function of the selected (v) items of y
version 1
13 - ((2 : '[ u v { ]' ` ].) (`])}) 1: i.5
0 12 2 3 4
There appears to be a rule that modifier trains that are longer than 3 "tines"
will be grouped from left to right in 3s
above is (C C C) A A . This allows fewer parentheses since they will be auto
added
2 : '[ u v { ]' ` ]. (`])}
(2 : '[ u v { ]' ` ].) (`]) (} )
and even
2 : '[ u v { ]' ` ]. `]} NB. C C C C V A -> ((C C C) C V) A -> CA =
rational pre-903 modifier trains.
((2 : '[ u v { ]' ` ].) ` ])(} )
version 2: enhance the ammend conjunction to work monadically. u dyadic
function called monadically has access to both selected items and whole list as
right arg.
extending to right end without parens works (adding ~ reflect, and switching
some internal [ ])
2 : '] u v { [' ` ]. `] }~ NB. CAA
((2 : '] u v { [' ` ].) ` ]) (} ) ~
but this lack of parentheses elegance is only due to CCV -> CA
if instead, this is written as CAAA, it becomes (CAA)A, and still works
2 : '] u v { [' ` ]. (`[) }~
((2 : '] u v { [' ` ].) (`[) (} ))~
13 -(2 : '] u v { [' ` ]. (`[) }~) 1: i.5
0 12 2 3 4
ABER = Always be extending right. You can parentheslessly extend a modifier to
the right with A or C (u = v or n)
version 3: allow v (selection verb) to be a noun by adding "_ modifier to "selection
tine" of }
our versions so far are in C C C C V A A format, and we need to modify the 3rd
C from left. This won't work
2 : '] u v { [' ` ]. "_
because that is (C C C) C N which applies "_ to whole expression instead of just
middle tine of } gerund. so C C (C "_) is what we are looking for
2 : '] u v { [' ` (]."_) (`[) }~
((2 : '] u v { [' ` (]. " _)) (`[) (} ))~
13 -(2 : '] u v { [' ` (]."_) (`[) }~) 1 i.5
0 12 2 3 4
version 4: replace the explicit conjunction left part with a tacit one
sketching it out before worrying about "AC problems" or parenthesing,
[` ` `{`[
(([ ` `) ` ({ )) ` [
appears correct because UCC does what AC "should" do. There is a bug with our version 3
enhancement. A noun argument will blow up the "` trains"
-(]` ` `{`[ `: 6) 1:
] - 1: { [
ar =: 1 : '5!:1 <''u'''
and CCA can replace our dangling ` (C)
-(]` ([. ` ar) `{`[ `: 6) 1
] - 1 { [
amend =: ]` ([. ` ar) `{`[ `: 6 ` (]."_) `[ }~
13 - amend 1 i.5
0 12 2 3 4
This seems very clean only because uCC behaves as the rational AC. If you make
the mistake of parenthesing the initial (]`) then transforming to ACA format is
only manageably dirtier because the starting state is clean
- ((]`) ([. ` ar) ]. `{`[ `: 6 ` (]."_) `[ }~) 1
(] - 1 { [)`(1"_)`[} ~
On Sunday, December 12, 2021, 02:15:03 p.m. EST, 'Pascal Jasmin' via Programming
<[email protected]> wrote:
I'd like the following changes to new modifier trains in priority order:
AC -> uACv
CC -> (uC1v)C2
u`n and m`v producing gerunds instead of errors when n or m is unboxed and not
''
J is a powerful language in large part due to its existing modifier support.
It allows easy composition of functions and modifiers. The new trains,
especially ACA and CA are a significant enhancement of that composition power.
These new/old trains also make writting compound modifiers much easier.
Thank you to J team for reviving the old trains.
With J's strong capabilities for composition, the primary purpose of writing a
modifier is an expectation for general (re)use. And the value of the whole
system is in the ease of composition and editability.
If you want to create the (current) behaviour of AC, you can easily write 1 :
'uACu' or tacitly, ((A C [.)a:) . And this, likely very rare use case, is
then available for full composability by you and users.
Composability means 2 things. Easy function composition, but also, an easily
editable writing process.
+(``:6)#
+ #
The current way to extend this CA (CCV -: CA) with adding say a / modifier to u
is to shoehorn the expression into ACC format: (AC].)
+ (/(``:6)].)#
+/ #
That extra ]. all the way at the "other end (right)" of the C part in AC is a needless
"nightmare"/composability obstrction in comparison to "forcing extra steps" for the less
useful current AC definition.
One improvement would be to define AAC (currently undefined) as u(AA)(Cv) and AAAC
as (AA)AC because then composing an adverb to left of modifier train would only
require an extra annotation (A ]: C) that does not require cursoring over and may
also not require an abundance of parens. There is a readability problem as well
when the }bookkeeping annotation" ]: or ]. is not next to the leftmost modifier
Reading a modifier must be done left to right. The right parts compose on the
results of the left parts. Calculating the order (number of parameters) of a
modifier both mentally and mechanically is easier when most, and the simplest
(AC CC ACA and CA) are all conjunctions until observed verb/nouns bind them.
When encountering left to right AC, having to mentally or mechanically
compute/find whether there is a ]. in appropriately parenthesized location is
taxing and distracting.
CC as a hook generator is marginally useful. (``:6) would do the same, and if ` produced
gerunds with m`v and u`n for unboxed and non empty m and n, then producing (u n) from CC
"replacement" is also easy. A user defined conjunction ti can replace `, but
it requires explicit code that pollutes display on partial bindings.
+`(1 ar)`] creates a display ugliness that +`1`] would not.
it might also be worth enhancing } such that
+`(1 ar)`]}
|domain error
didn't happen, and +`1`]} would be legal and would display as written. }(amend)
is a critical language function that could be easier to use. v0`v1`v2 could
also be a monadic version of amend.
The proposal for CC -> ((u C1 v)C2) supports the need for a modifier/modifier
train to have more than 2 parameters. Proposed CC would have order of 3.
A current workaround for achieving the desirable behaviour is to create a CA
train with the compound modifier
CasA =: 1 : ' 1 : ('' u '' , m ) '
# +/( ` ('`'CasA)) %
┌───────┬─┬─┐
│┌─┬───┐│%│#│
││/│┌─┐││ │ │
││ ││+│││ │ │
││ │└─┘││ │ │
│└─┴───┘│ │ │
└───────┴─┴─┘
to make a train out of the gerund (`:6) the "easiest" solution is to modify the CA train to CAA,
but the "most appropriate"/extensible solution is to treat (`:6) as an "optional"/end
transformation function to be tacked on or removed for debugging or inserting further modifiers in between
# +/( ` ('`'CasA(`:6))) % NB. easy less extendible way
+/ % #
# +/(( ` ('`'CasA))(`:6)) % NB. extensible but requires extra parentheses with
cursoring around to envelop previous expression
+/ % #
extending the function using current AC workaround to put the / adverb inside
the modifier instead of the caller's responsibility:
# +(( (/ ` ]:) ('`'CasA))(`:6)) %
+/ % #
as proposed for CC this core would become (` `) and the alternative for train
formation ((` `)`:6) is much neater starting point from which to insert
additional expansions/modifiers. The enhanced modifier above becomes
(((/`)`)`:6)
Making general modifier composability "the bias" is a worthwhile focus of the
language. Shortening the space between parentheses and reducing the total number means
improvements in writability and readability, and extending the expression complexity that
is mentally manageable.
On Tuesday, October 5, 2021, 12:24:44 p.m. EDT, Pascal Jasmin
<[email protected]> wrote:
HR: I found the production (A C)->((x A) C x) useful enough in my work
that I gave it a name, the adverbial hook.
One way to keep this production, which I still fail to see as "useful enough",
while enhancing composability of modifier trains is defining
AAC -> u AA(Cv)
implying that
AAAC -> (AA)AC and A(AAC) -> (AA)AC
Parenthesized (AC) can retain your quirky production.
if you have an A and a C that you wish to "compose intuitively", ]:AC has
better future composability than the ACA transformation of AC]: due to parentheses
explosion described below.
A yet to mention advantage of composability is the ability to test individual
modifier trains before combining them simply. The AAC and ]:AC proposals would
do this, in a way that shoehorning a modifier into ACA form does not. ie.
composing a modifier train to the left of ACA requires a new shoehorning into a
new ACA structure.
Assuming the above is sensible, and in the spirit that more trains are good, there are a
couple of other "smelly" current train defintions. Smelly for reusing
arguments:
ACC -> uA C (u C v)
CCA -> (u C v) C (vA)
it is worth noting that current AC could also be written as ((AC[.)a:)
but some productions that are missing that would include a CC component in a
train are
(uC)(vC)
(Cu)(Cv)
(uC)(Cv)
(Cu)(vC)
ACC and CCA could cover 2 of them. CAC could cover a 3rd.
On Monday, October 4, 2021, 08:44:11 p.m. EDT, 'Pascal Jasmin' via Programming
<[email protected]> wrote:
I have to be repetitive in first part of response because it seems to have been
missed in later discussion
``:6 is all that is needed to produce a hook.
a replacement to ` that forms gerunds out of m`n or m`v or u`n is needed. I call that
replacement "ti".
That is needed for the u n execution example of your CC. The only reason you
would ever need a modifier to execute u n (or y) is if u returns a string that
needs to be processed by another modifier (such as 1 : or 3 : ) in order to
produce a function.
Therefore all uses of implemented CC are served by ti(`:6)(optional extra
Adverb to process a noun result)
USE CASE (as requested)
All 902 modifier trains are composable by simple juxtaposition. AAA and A
compose with whichever is positioned on the left will send its result to the
one on the right. Composability is high value awesomeness!
My CC proposal keeps that composability for the new enhanced modifier trains
that include CA and ACA (both conjunctions)
forcing (AC[:) as a replacement for what should just be AC harms composability
as well:
A (AC[:) has to be written as A (AC[:) [: . Adding a further A to left means
(A (A (AC[:) [:) [:) if as an example all of the As and ACAs were named, and
you couldn't just go inside the ACA to do ((AAA)C[:)
I don't believe conjunction reflexitivity is worth the composability nightmares.
Reducing parentheses is not a laudable goal; in fact, I see it as the
opposite. The train A A C should, if possible, mean something different
from (A A) C because Why have two ways to say the same thing?
AAC is not defined, btw, but if it were I would strongly hope that it were
(AA)C]: ie what (AA)C and AC should be.
It is a respectable philosophy to have unique trains that force explicit
parentheses. I would prefer fewer parsing rules with auto pairing of
parameters for the pure blissful cleanliness of it all (but not insisting on
the full purity extreme). Your view forces a lot of memorization that might
have been an important factor in the original decommissioning.
On Monday, October 4, 2021, 06:05:47 p.m. EDT, Henry Rich
<[email protected]> wrote:
The discussion is moving toward the polemic and unhelpful. I write to
try to suppress suggestions that have no hope of being implemented soon.
1. Reducing parentheses is not a laudable goal; in fact, I see it as the
opposite. The train A A C should, if possible, mean something different
from (A A) C because Why have two ways to say the same thing? We are
trying to define a grammar with NO reserved words except parentheses;
perhaps only Ken could have attempted it; there are just a handful of
productions to define; they should be as powerful as possible, with as
little duplication as possible.
2. I found the production (A C)->((x A) C x) useful enough in my work
that I gave it a name, the adverbial hook.
3. (C C) -> ((u C v) C) is a drastic change to the language. It consumes
two words and creates something that consumes one or two more words. Is
it brilliant? Is it the camel's nose in the tent? I personally think
it raises a stench to the nostrils of the Almighty. I could be wrong.
But anyone suggesting such a fundamental change must arrive first with
SHORT EXAMPLES showing why the language should consider such forms,
which will be so unfamiliar to the J programmer. If the knowledgeable J
community is convinced, we can consider whether the forms should be
implemented.
A couple of users (including me) suggested (C0 C1)->((u C0 v) (u C1
v)). Why? Because it allows
* easy production of hooks, with V ([. ].) V
* execution of verbs, with V ([. ].) N-phrase
That's a pretty good argument, SUPPORTED BY EXAMPLE. Hooks are important.
I am very reluctant to make changes that don't have demonstrated
benefits, being a disciple of Omar:
O take the cash in hand and waive the rest;
Ah, the brave music of a /distant/ drum!
Henry Rich
On 10/4/2021 4:33 PM, 'Pascal Jasmin' via Programming wrote:
That said, this was also a syntax error when we did not have
conjunction trains. So I am not sure why it should be an important
issue now.
if you stick to old permissible AA...A trains then you don't need to "over"
bracket (AA..A)
for CAA..A you also don't need to bracket (for practical purposes)
for AA..ACA, you do need to over bracket the left part.
There are new powers that allow including unbound Cs inside adverb trains.
That is awesome!!! The disadvantage of imposing tedium on these new powers is
greater than the advantage of not double typing out u in uCu, in my opinion.
On Monday, October 4, 2021, 04:20:13 p.m. EDT, Raul Miller
<[email protected]> wrote:
Hmm...
Conceptually speaking, the A A C A syntax error could be eliminated
without the addition of any new parsing rules, if A A C would
translate to two parse elements (combining the two adverbs and putting
the C back as-is).
That said, this was also a syntax error when we did not have
conjunction trains. So I am not sure why it should be an important
issue now.
I also don't know if there are other implications. I haven't thought
about it that much.
Are you aware of other important cases?
Thanks,
--
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