It's not clear to me what you want to accomplish here - no sample data, no
results. Also note that while this is, in a sense, tacit, you'll get some
... interesting (and probably unintended) behaviors if you try using your 3
: and/or 4 : verbs with rank.
I've got some code I'm working on which uses variables in a tacit
expression. Here's an example:
mergetable=:2 :0
:
tinds=. 1+i.#m
ginds=. -1+i.#n
tlen=. {:@$x
glen=. {:@$y
mergecol=. [:`tonly`both`gonly@.(3&#.@:*)
tget=. {&x@<:@{.@(#~ 0&<)
gget=. {&y@<:@|@{.@(#~ 0&>)
tnul=. (tlen#a:)"_
gnul=. (glen#a:)"_
tonly=. tget,gnul
gonly=. tnul,gget
both=. tget,gget
(m,n) mergecol/. tinds,ginds
)
Example use:
(i. 4 3) (;:'this is a test') mergetable (;:'that is not like
this')&:(]each) p:i.5 2
┌─┬──┬──┬──┬──┐
│0│1 │2 │23│29│
├─┼──┼──┼──┼──┤
│3│4 │5 │5 │7 │
├─┼──┼──┼──┼──┤
│6│7 │8 │ │ │
├─┼──┼──┼──┼──┤
│9│10│11│ │ │
├─┼──┼──┼──┼──┤
│ │ │ │2 │3 │
├─┼──┼──┼──┼──┤
│ │ │ │11│13│
├─┼──┼──┼──┼──┤
│ │ │ │17│19│
└─┴──┴──┴──┴──┘
~.;:'this is a test that is not like this'
┌────┬──┬─┬────┬────┬───┬────┐
│this│is│a│test│that│not│like│
└────┴──┴─┴────┴────┴───┴────┘
In other words, this addresses the problem of "given two tables with
different column headers, build a bigger table with combined headers and
all the rows from each table."
I put the table on its side (so columns are J items), but the interesting
thing, here, is that I am using numeric indices to refer to external data.
You'd want to transpose the table to show rows and columns more
traditionally. (I'm using boxes here because "in real life" I am working
with text rather than numbers.)
This particular example allowed me to use (in this case) J's /. adverb
without actually asking it to manipulate the data which I am grouping
together. (Though in this particular example, I've brought everything
together in the final result - this let me use J's error detection features
in a way which would not have worked if I had left the data in external,
"explicit" contexts.)
Thanks,
--
Raul
On Tue, Mar 18, 2014 at 12:26 PM, Pascal Jasmin <[email protected]>wrote:
> Here is a neat way to get intermediate results within a tacit expression.
> Many drawbacks, but it is possible. Drawbacks include global variables,
> and dyad vs. monad must be known prior to access:
>
> 3 : 'c' + [ 4 : 'c =: x * y' ]
>
> That may not look very tacit, but it is :P intermediate result c is
> accessed later in the fork.
>
> the biggest drawback is accessing the result (3 : 'c') If the access is
> in a dyadic part of the expression, it needs to be (4 : 'c')
>
> Any improvements?
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