The syntax is that of explicit J but missing some things, like control
words and assignment, and perhaps the ability to write multiline
expressions. If it produces tacit J, it's also not going to be able to
define modifiers.
I just don't see that having a new way to write tacit verbs is a change
worth making, if it doesn't allow something that the old way didn't.
Henry Rich
On 9/27/2017 6:25 AM, Erling Hellenäs wrote:
Hi all !
See comments below.
Henry, you answered one of three questions.
Cheers,
Erling
On 2017-09-27 11:09, Henry Rich wrote:
I have trouble contributing to this because I don't understand your
proposal as written. One thing I don't understand is why you call
your new verbs 'tacit'. It appeared to me that they used ] and [ as
tokens indicating the input arguments. That would make them
explicit, by the definition of that word.
We can call them something different, I just choose tacit-v
expressions for the purpose of my request.
They are very similar to tacit expressions. They have exactly the same
functionality, just different syntax, and that syntax is the syntax of
explicit J.
The tacit language shows up inside lines of code. When you write
sortedbycol1 =: (/: 1&{"1) array
there a little tacit code there. We wouldn't want to lose that.
The tacit-v expression would be
sortedbycol1 =: (: ] /: 1 {"1 ] ):
if we choose the (: ): brackets. The brackets are needed here as long
as present tacit J is the default.
The tacit-t version can be written like this.
sortedbycol1 =: /: 1&{"1
Brackets are automatically added, creating the hook. If we directly
compare the notation,
] /: 1 {"1 ] is equivalent to
( /: 1&{"1 )@] if we write code that can be moved between a monadic
and dyadic context without rewrite.
However, as I said, the easiest implementation probably is to continue
allowing the present tacit expressions in tacit-v expressions.
In the long run you would probably not want both ways to express
exactly the same thing, you would want to let the new tacit-v
expressions replace the present tacit expressions as I see it. There
is a question about how it could be done. One way is to not allow them
in tacit-v expressions from the beginning, as I propose, but there are
other ways. To block them from the beginning would make the first
implementation much harder.
sortedbycol1 =: (/: 1&{"1)
sortedbycol1 i. _3 4
0 1 2 3
4 5 6 7
8 9 10 11
All the uninflected delimiters are taken, and {. }. and {: }: and <.
>. and <: >:; but (. ). and (: ): are available.
It seems out of the question to redefine any of { } [ ] as they are
used in so much existing J code.
Henry Rich
On 9/27/2017 4:33 AM, Erling Hellenäs wrote:
Hi all!
It seems like fast function definitions is only for creating
explicit J verbs, adverbs and conjunctions?
This means it is only vaguely related to my proposal of tacit verbs
with explicit J syntax?
Maybe the fast function definition discussion should therefore have
it's own thread?
Let's say we wanted to implement tacit-v verbs.
-Is there a construct like { ... } or (. ... ). that could possibly
be used for a new kind of bracket notation?
-Would x and y or [ and ] be suitable as symbols of the left and
right arguments? If so, which of them ? If not, what would be a
suitable representation of the left and right argument ?
-Could the interpreter be easily modified to allow the explicit J
syntax in this new bracket construct, or would it be difficult or
impossible to achieve?
In the JWithATwist interpreter the difference between how brackets
with explicit J code are handled and how tacit-v brackets are
handled is about four lines of code. It think this indicates that
this might not be such a revolutionary change in terms of actual
code changes.
Cheers,
Erling
On 2017-09-26 22:34, Henry Rich wrote:
Good point, colorization. I never thought about that.
The big difference between Fast Functions and 3 : functions is that
Fast Functions are recognized when a script is loaded, instead of
when the 3 : is executed. It is the fact that 3 : is executed like
any other conjunction that prevents nesting of multiline verbs: the
nested verb can't be defined until it is executed, and by then its
definition is long gone.
The innermost (. ). is analyzed and replaced by (m : string). The
process continues for all nesting levels. This completes the prepass.
The generated verbs - (m : string) forms - are handled as they are
now, when the : is executed. That means nested verbs are not
processed until they are encountered during execution.
Linear representation is used to make the (3 : string) form atomic.
Yes, you would need to balance (. .
Henry Rich
On 9/26/2017 4:02 PM, Raul Miller wrote:
Prepass means essentially that this happens after word formation but
before parsing. That does eliminate some problems, but creates new
ones. It also suggests that you would be supporting explicit control
words. But it also means that you need to put a lot more thought into
how these would be represented (and stored) - there's no inherent
point to using linear representation to "unparse" here.
(Do inner (. ). definitions get reparsed every time the outer
expression gets evaluated? That might be the simplest approach, but
does require significant changes in explicit handling.)
Multiline means that you get into behavior somewhat like you get when
m :0 appears on a line. But getting out of that might be more
complicated than it is now (because you might not know if you need ).
or a sequence of them or ) to end it - for example after pasting
something big into your session).
The complexities introduced by multi-line probably means that
interactive environments would want to colorize (. ). definitions
(especially incomplete definitions while being entered) based on the
presence/absence of mnuvxy seen so far (probably not the current line
though).
Thanks,
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