neat.
tie
,^:(0:``)
tie&'' f.
,^:(0:``)&''
which is using the gerund (v1`v2) version of ^: . This appears to be
undocumented in that v2 here is a conjunction(`). I assume that using an
adverb as v2 is impossible?
The other peculiarity is that v1 is 0: which means that , never executes. Is
that right?
----- Original Message -----
From: Jose Mario Quintana <jose.mario.quint...@gmail.com>
To: Programming forum <programm...@jsoftware.com>
Cc:
Sent: Friday, February 21, 2014 11:31:56 AM
Subject: Re: [Jprogramming] Generating code from templates
The verbalized conjunctions tie and rank can be produced as follows:
9!:14 ''
j701/2011-01-10/11:25
Cloak=. (0:`)(,^:) NB. Conjunction to cloak adverbs and conjunctions as
verbs
Cloak=. (5!:1@<'Cloak')Cloak NB. Cloaking Cloak
'tie rank'=. (Cloak @: < each) @: ;: '` "' NB. Cloaking tie (`) and rank
(")
cf=. {.@(tie&'')@(rank&_)"0 f.
100"_`(200"_)`(300"_) -: cf 100 200 300
1
Cloak can also be produced without using ^: (although with a caveat).
Members interested in following the beginnings of the story can look at
http://www.jsoftware.com/pipermail/programming/2013-March/031883.html .
On Thu, Feb 20, 2014 at 8:52 PM, Raul Miller <rauldmil...@gmail.com> wrote:
> This would be more fun if you provided definitions for tie and rank (and
> others you use) in an addon.
>
> Without that, it feels like deus ex machina (and does not execute for me
> like it does for you).
>
> Thanks,
>
> --
> Raul
>
>
> On Thu, Feb 20, 2014 at 6:06 PM, Jose Mario Quintana <
> jose.mario.quint...@gmail.com> wrote:
>
> > "
> > Anyway, thought I'd share, and see if anyone else has useful tools for
> > manipulating J code (metaprogramming).
> > "
> >
> > Dan, I will try to show some meta-programming exercises soon. I am
> jumping
> > into the darkness hoping that I will land well; so far, so good. In the
> > meantime, the following is a F^4 underground verb corresponding to Raul's
> > explicit verb (using verbalized primitive conjunctions):
> >
> > cf=. {.@(tie&'')@(rank&_)"0 f.
> >
> > 100"_`(200"_)`(300"_) -: cf 100 200 300
> > 1
> >
> >
> >
> > On Thu, Feb 20, 2014 at 2:39 PM, Dan Bron <j...@bron.us> wrote:
> >
> > > There was a question on StackOverflow today on generating constant
> > > functions from the items of an array. As in, 100 200 300 <==>
> > > 100"_`(200"_)`(300"_) .
> > >
> > > As a more general question, how can we specify code templates and then
> > use
> > > them to dynamically produce gerunds for later execution? *
> > >
> > > Here's one idiom I've found useful in such situations:
> > >
> > > substit =: [^:(__-:])L:_ 0
> > >
> > > template =: __"_ NB. The template; note the __
> > > TEMPLATE =: {. template f.`'' NB. Atomic rep of template
> > >
> > > GERUND =: TEMPLATE substit"_1 _~ 100 * 1 + i.3
> > >
> > > GERUND`:6
> > > (100"_) (200"_) 300"_
> > >
> > > GERUND@.0
> > > 100"_
> > >
> > > GERUND@.2 'hello'
> > > 300
> > >
> > > The basic idea is to "fill in the blanks" in the template with the
> > inputs.
> > > Here, the blank is __ (negative infinity), so we look for that in the
> > > gerund template, and when we find it, we replace it with the input. I
> > kind
> > > of like how the verb does this: first, we only bother looking at level
> 0
> > > (because __ is unboxed, so it will never appear above level 0), and
> > > second, the verb is passive until __ is detected (because ^:(]-:__) is
> > > ^:0, i.e. "do nothing and just return the RHA" until then).
> > >
> > > One possible issue is what we use to denote "blank". If we're going to
> > > allow users to pass in any gerund, then he could potentially want to
> > > include __ as part of the code to be produced, rather than replaced.
> > There
> > > are a couple possible ways to address that limitation. First, we could
> > use
> > > a value which a user is very unlikely to want to produce (as opposed to
> > > replace), i.e. _. :
> > >
> > > substit =: [^:(1-:128!:5@])L:_ 0
> > > SPARTA =: ({. _."_ `'') substit"_1 _~ 300
> > > SPARTA`:6
> > > 300"_
> > >
> > > Or, we could define substit as an adverb (adjective), which takes the
> > > "blank" as an argument:
> > >
> > > Substit =: (-:&) (@]) ([^:) (L:_ 0)
> > >
> > > substit =: 'blank' Substit
> > > substit
> > > [^:(-:&'blank'@])L:_ 0
> > >
> > > ; , ((< {. 'blank'&;`'') substit~&.> ;:'fill in the blanks' )`:0 '!'
> > > fill!in!the!blanks!
> > >
> > > But if we do that, we have to start wondering about the 0 in L:_ 0 ,
> > > because the user's "blank" might be boxed, and therefore have L.>0 . Of
> > > course, we could fix this up by making the L: dynamic:
> > >
> > > Substit =: adverb : '[^:(m-:])L:(_,L.m)'
> > >
> > > NOTNULL =: ({. ~:&a:` '') a: Substit~ <'#N/A#'
> > > NOTNULL`:6
> > > ~:&(<'#N/A#')
> > >
> > > But it might be more fun to go meta-meta:
> > >
> > > (({. substit f.`'') substit~ _999)`:6
> > > [^:(_999 -: ])L:_ 0
> > >
> > > Here, define the "standard" blank to be __, and then let the user
> change
> > it
> > > by using substit :)
> > >
> > > Anyway, thought I'd share, and see if anyone else has useful tools for
> > > manipulating J code (metaprogramming).
> > >
> > > -Dan
> > >
> > > * For a recent example of where such metaprogramming might be useful,
> or
> > > convenient, see the postscript of:
> > >
> > >
> > >
> http://www.jsoftware.com/pipermail/programming/2013-December/034373.html
> > >
> > > Other examples can be found with a forum archive search for the string
> > L:0
> > > _
> > > ----------------------------------------------------------------------
> > > 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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>
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