> Perhaps one should consider that, rightly or otherwise, 0. currently has a
meaning according to the interpreters (e.g., j902),
Not that long ago, it used to give an error. Never noticed the change.
A problem that comes up enough to be annoying when defining 3.. or other . :
inflections to numbers is that
;: '3.. 2'
┌─────┐
│3.. 2│
└─────┘
subsequent numbers is the same word.
Avoiding this problem, is a pretty easy change to ;: parser, and costs
"nothing" when 3. is a J error, but when 3. was previously valid code, can
create new problems. Still worth the change for me (as a dsl) though.
You might prefer your definitions to be
1&{::@]
This allows intuitive dyadic use case for y, and allows B~ to access x argument
fields.
On Tuesday, September 14, 2021, 07:31:21 p.m. EDT, Jose Mario Quintana
<jose.mario.quint...@gmail.com> wrote:
> 0. to 9. and/or _9. would make good additions to language.
Perhaps one should consider that, rightly or otherwise, 0. currently has a
meaning according to the interpreters (e.g., j902),
0.
0
Often I use an adverb (mne) to define undefined names, or redefine existing
proverbs, as pointers to fetch a corresponding content of a box within a
state consisting of a list of boxes. For example,
(A B C D)mne
would, as a side effect, define A as 0&({::), ... D as 3&({::). Thus,
C
2&({::)
Another adverb (f) allows one to use the proverbs to get multiple boxes
from the state,
(B C)f
1 2&{
and a conjunction (h) allows one to amend the contents of the state in
terms of the proverbs,
(A B) h ((B C)f)
1 2&{ 0 1} ]
or
C h (B +/ .* D)
<@:(B +/ .* D) 2} ]
The following illustrates their use,
( S=. 0 ; 1 2 ; '...' ; 1j1*(i.2 3) )
┌─┬───┬───┬───────────┐
│0│1 2│...│ 0 1j1 2j2│
│ │ │ │3j3 4j4 5j5│
└─┴───┴───┴───────────┘
C S
...
(B C)f S
┌───┬───┐
│1 2│...│
└───┴───┘
(A B) h ((B C)f) S
┌───┬───┬───┬───────────┐
│1 2│...│...│ 0 1j1 2j2│
│ │ │ │3j3 4j4 5j5│
└───┴───┴───┴───────────┘
C h (B +/ .* D) S
┌─┬───┬─────────────┬───────────┐
│0│1 2│6j6 9j9 12j12│ 0 1j1 2j2│
│ │ │ │3j3 4j4 5j5│
└─┴───┴─────────────┴───────────┘
I define tacitly mne, f, and h (moreover, mne f and h themselves are tacit
entities) via the unorthodox methods using a fork of J which I have
mentioned in the past. However, I cannot see any reason why mne, f, and h
could not be defined (explicitly, when necessary) using the latest public
interpreters.
On Tue, Sep 14, 2021 at 1:18 PM 'Pascal Jasmin' via Programming <
programm...@jsoftware.com> wrote:
>
>
> in jpp project,
>
> I use 0. as shortcut for (0 {:: ]) and 1. as shortcut for (1 {:: ])
>
> The adverb G =: 1 : 'u {:: ]' is the same.
>
> 0.~ or 0 G~ can be used to access fields of x argument.
>
> "State of something complicated" can simply be several boxed fields in x
or y argument.
>
> What easy accessors do is also permits "intermediate tacit results" by
prepending a calculated box to the y argument, with easy unpacking later in
the verb.
>
>
> 0. to 9. and/or _9. would make good additions to language.
>
>
>
> On Tuesday, September 14, 2021, 12:06:37 p.m. EDT, Michal Wallace <
michal.wall...@gmail.com> wrote:
>
>
>
>
>
> Let me amend what I was just saying about name:: ...
>
> I have been experimenting with a tacit style where the y "argument"
> represents the state of some big complicated object or system... for
> example, the state of a parser or a virtual machine.
>
> I've found that "accessor" verbs are really handy, and allow you to
> decouple your tacit code from the actual implementation of the object.
>
> An accessor 'gsn' (for "get/set 'n'") is a ambivalent verb that works like
> this:
>
> gsn y -> ignore y and return S
> x gsn y -> ignore y. sets n to x and return S
> S here indicates whatever the "state of the whole system" is...
>
> 'gsn' here is a pronoun (proverb?) -- If you had three state variables
> n0,n1,n2,
> you would make three such verbs, gsn0, gsn1, gsn2.
>
> This is quite flexible. If you want to store the state of your system in
an
> object or namespace,
> you can implement gsn like so:
>
> gsn0 =: {{ n0__state }} :: {{ n0__state =: x }}
>
> Then the y argument you pass is just '' or whatever you want, since it's
> ignored.
>
> Or you can choose to implement the state as some physical array structure,
> which gets accessed and modified in place:
>
> gsn1 =: {{ 1 { y }} :: {{ x 1 } y }}
>
> It would be nice if these accessors could be created automatically.
>
> For example, (if we weren't about to be using the syntax for 'self
effacing
> names', we might
> use name:: to work as the accessor)... And then:
>
> name:: y could:
> - invoke name__y if y is a reference
> - extract they value for key 'name' from y if y is some kind of
dictionary
> - extract n { y if 'name' is defined as a constant number
>
> x name:: y would do the analagous things for setting the value to x.
>
> Many object-oriented languages (python, C#, javascript) give you the
> ability to define such accessors either for specific names, *or* to design
> generic accessors that take the name as a parameter.
>
> For example, in python, you can arrange for y.x = n to do any of the
> following:
>
> 1. explicitly set the x attribute of object y to n (no accessor
defined)
> 2. call a specific y.set_x(n) method
> 3. call a generic y.__setattr__(key='x', value=n) method
>
> My proposal is that x name:: y would have similar range of features,
> depending on the presence of certain handler verbs in the implicit locale
> (if y -: '') or on y itself.
>
> Likewise, 0:: 1:: _1:: etc could be recognized as 'index accessors'
> when y is an array.
>
> If you wanted to get really crazy, then ( index ):: could produce an
> explicit accessor function, where index is some noun that could be passed
> as m in m { y.
>
> This final form could perhaps even use the incredibly convenient "subarray
> notation" of x ;. 0 y , (which is an amazing "getter" but AFAICT, has no
> "setter" equivalent )
> https://code.jsoftware.com/wiki/Vocabulary/semidot0#dyadic
>
> Here is some example code (parser combinators) that uses the "y is a
> structure" concept, where the pattern makes it very handy to implement
> backtracking.
> https://github.com/sabren/b4/blob/master/j/parseco.ijs
>
> Here is another example (virtual machine) using the "y is ignored" style,
> where the accessors get and set locale variables.
> https://github.com/sabren/b4/blob/master/j/b4.ijs
>
> This one in particular uses the idea to partition the virtual machine
> instructions into two sections.
> The "microcode" provides accessor functions that get and set registers,
and
> then
> the "instruction set" is defined in terms of these operations.
> This way I can decouple the instruction set from the actual implementation
> of the virtual machine's internals.
>
> Right now it just stores registers and memory cells in separate variables,
> but an alternate implementation might instead store everything in one big
> memory-mapped file, so the machine state could persist on disk or be
shared
> between different processes, and this would only require swapping out the
> "microcode" layer.
>
> Anyway, I know the syntax part of this is still a half-baked proposal, but
> the actual idea is very usable now, and pretty fun to use.
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