original verb2conjunction definition
lrA =: 1 : '5!:5 < ''u'''
v2c =: 1 : ' 2 : (''m '' , u lrA , '' n'')'
Something I just figured out in J, is that the u"_ trick to pass either a noun
or verb to a modifier does not need to be resolved at "compile/definition
time", and can still be used to return a tacit result. so new definition of v2c
fork =: 1 : ' 2 : (''u"_ '' , u lrA , '' v"_'')
This turns v2c into a fork, with the extra capability of parsing N V N, and V V
N as a fork.
1 (5 ;fork 4 (; fork) [ (; fork 3) ; ] ) 2
┌─┬─────────┬─┐
│5│┌─────┬─┐│2│
│ ││┌─┬─┐│3││ │
│ │││4│1││ ││ │
│ ││└─┴─┘│ ││ │
│ │└─────┴─┘│ │
└─┴─────────┴─┘
from the above note the leftmost side without any parens is parsed exactly as
if v2c was not there. This is because v2c is an adverb, and so the right side
is parsed before it is. The other 2 calls to v2c do change the parsing to that
of a conjunction.
(5 ;fork 4 (; fork) [ (; fork 3) ; ] )
5"_ ; (((4"_ ; ["_)"_ ; 3"_) ; ])"_
while typing (; fork) to bind arguments closest to it, does not reduce the
total number of parentheses, by keeping the parenthesis close together, it can
make a line more readable than widely spread deeply nested parenthesis. The
above has the fork version more readable than its result, and it is faster to
touchtype than shift90, and cursoring around.
A reason to not replace v2c entirely is that v2c returns a noun while fork
returns a verb. fork can be used inside a tacit expression with dependable
results, but v2c will be more intuitive outside of a tacit expression
linkC =. ;v2c
linkF =. ;fork
5 linkC 1 linkC 2 ;4
┌─────────┬─┐
│┌─────┬─┐│4│
││┌─┬─┐│2││ │
│││5│1││ ││ │
││└─┴─┘│ ││ │
│└─────┴─┘│ │
└─────────┴─┘
(5 linkC 1 linkC 2 linkF ]) 4
┌─────────┬─┐
│┌─────┬─┐│4│
││┌─┬─┐│2││ │
│││5│1││ ││ │
││└─┴─┘│ ││ │
│└─────┴─┘│ │
└─────────┴─┘
5 linkF 1 linkF 2 linkF 4 a:
┌─────────┬─┐
│┌─────┬─┐│4│
││┌─┬─┐│2││ │
│││5│1││ ││ │
││└─┴─┘│ ││ │
│└─────┴─┘│ │
└─────────┴─┘
----- Original Message -----
From: Pascal Jasmin <[email protected]>
To: "[email protected]" <[email protected]>
Cc:
Sent: Saturday, August 2, 2014 10:34:21 AM
Subject: Re: [Jprogramming] parsing abuse, verb to conjunction
thank you Raul,
I do have a workaround for this issue:
3 (4 :('assert. y>0 label_. assert. x>0 label_. x+y') v2c) 2
5
inserting label_. creates an internal multiline parsing without the multiple
lines.
Can automatically convert to the format too:
cutdef
=: (0 :)(1 : 'cutLF m')
boxscan
=:((&.>)/)(>@:)
('assert. y>0';'assert. x>0';'x+y') cutdef
┌───────────┬───────────┬───┐
│assert. y>0│assert. x>0│x+y│
└───────────┴───────────┴───┘
4 : (([, ' label_. ',])boxscan ('assert. y>0';'assert. x>0';'x+y') cutdef)
4 : 'assert. y>0 label_. assert. x>0 label_. x+y'
Linda, in terms of selling it:
Its a simple way to write a conjunction. If you assign it to a name, then
users can use it as a conjunction without parens.
There aren't that many examples of writing an adverb that returns a
conjunction. This simple one can enlighten us in how such adverbs could be
used, and provide a template for creating more advance ones.
As a DSL tool, it allows entry of data and code with potentially fewer parens,
and provide a left to right feel.
While there is always an equivalent way to write a function composition with
parens, it can provide a lazy way to extend a function composition. (A
conjunction grabs the first term to its right and processes before the rest of
the expression on the right... fairly similar to parens). With a naming
convention that clarifies a conjunction, this may be considered a cleaner way
to write a fork:
(2 appendC 1 + ]) 2
4 3
(2 , 1 + ]) 2
2 3
((2 , 1) + ]) 2
4 3
The main purpose for me though is extensible functional code generation.
Sometimes I want to extend a code string in a way that conjunction parsing
helps avoid inserting parens around part of the existing built code string, or
part of the new string, or parts of both.
Another parsing abuse example:
eval
=: 1 : ' a: 1 : m'
CONJ
=: 2 : ' u (v eval)'
CONJ takes a string representation of a conjunction to create an adverb that
will consume 2 arguments on its right.
If you wanted to have a dyadic verb parse both its arguments on the right:
4 (3) CONJ ', v2c'
3 4
(3 CONJ ', v2c')
(3)(2 : 'm , n')
is an adverb roughly equivalent to 3&, except it will take its argument on the
left instead of right.
The reason you might want that is composition of adverb trains, or composing
functions where you only get part of the information at a time, and flexibility
as to whether a verb or adverb can be inserted into a composition.
----- Original Message -----
From: Raul Miller <[email protected]>
To: Programming forum <[email protected]>
Cc:
Sent: Saturday, August 2, 2014 8:23:36 AM
Subject: Re: [Jprogramming] parsing abuse, verb to conjunction
Here is an issue to be aware of:
1 (4 :'x+y') 1
2
1 (4 :'x+y' v2c) 1
2
1 (4 :('assert. x>0';'x+y')) 1
2
1 (4 :('assert. x>0';'x+y') v2c) 1
(1) (2 : 0) 1
m 4 : 0
assert. x>0
x+y
) n
)
The problem is that 5!:5 does not do proper serialization of multi-line
explicit verbs. The result of 5!:5 is designed for use by 0!:0, and J is
perhaps too simplistic in this regard. (paraphrasing my understanding of
Ken Iverson's take on this issue: <<why would you want nested blocks? That
means you are not labeling things adequately, which leads to unreadable
code.>> though actually he would probably have said something far simpler,
like "why do you need that?")
Of course, many programmers love unreadable code, (consider ioccc as an
example). So maybe for their benefit we ought to have nested blocks and a
5!:7 serialization mechanism which can be used in ". contexts?
It's certainly something to think about, but it might be worth keeping in
mind that there will always be machine limitations and that for
computational symmetries to be valid they need someone to find a practical
use for them.
Thanks,
--
Raul
On Sat, Aug 2, 2014 at 12:35 AM, 'Pascal Jasmin' via Programming <
[email protected]> wrote:
> this adverb returns a conjunction which is designed to turn any dyadic
> verb into a conjunction purely for parsing convenience that a conjunction
> can sometimes provide.
>
>
> lrA =: 1 : '5!:5 < ''u'''
> v2c =: 1 : ' 2 : (''m '' , u lrA , '' n'')'
>
>
> 2 1 (, v2c) 3 + 4
> 6 5 7
> appendC =. , v2c
> appendC
> 2 : 'm , n'
>
> 2 1 appendC 3 + 4
> 6 5 7
>
> if you don't put parens around the adverb and its verb argument, then it
> treats the full y as the n argument to the resulting conjunction which is
> usually not what you want since that is what the original verb would do.
> But including one of the conjunction arguments inside the parens, turns it
> into an adverb which may provide useful parsing patterns.
>
> 5 , v2c 2 1 (, v2c) 3 + 4
> 5 6 5 7
>
> 5 , (2 1 3 + 4)
> 5 6 5 7
> 5 (, v2c 2 1) (, v2c) 3 + 4
> 9 6 5 7
> 5 (, v2c) 2 1 (, v2c) 3 + 4
> 9 6 5 7
> (5 , 2 1 , 3) +4
> 9 6 5 7
>
> 5 (, v2c) 3 (2 1 , v2c) + 4
> 6 5 9 7
>
> 4 + 2 1 &, 5,3
> 6 5 9 7
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
----------------------------------------------------------------------
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