H.]ere are Raul's two definitions, f and g and an explicit definition h
which is turned to tacit.
n=:2
d=:3
n(f=:4 : 'x>+:(?]) x#y')d
1 0 0
0 1 0
5!:4 <'f'
-- 4
-- : -+- ,:'x>+:(?]) x#y'
n(g=:[>[:+:[:(?])#)d
0 1 0
1 0 0
5!:4 <'g'
-- [
+- >
--+ -- [:
│ +- +:
L---+ -- [:
│ │ -- ?
L----+----+- ]
L- #
n(h=: 13 :'(-:x)>(]?])x#y')d
1 0 0
0 1 0
5!:4 <'h'
-- [:
----+- -:
│ L- [
+- >
--+ -- [:
│ │ -- ]
L---+----+- ?
│ L- ]
L- #
f
4 : 'x>+:(?]) x#y'
g
[ > [: +: [: (? ]) #
h
([: -: [) > [: (] ? ]) #
I don't know why it took so long to notice I could do that. You might find
it helpful.
Linda
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Bo Jacoby
Sent: Friday, November 02, 2012 7:16 AM
To: [email protected]
Subject: Re: [Jprogramming] Arc consistency in J
Hi Mike
You request comments regarding style. Style is a matter of taste, so don't
take my comments as criticism.
Your very first expression
(n%2)>(]?]) n$d
can be written without division:
n>+:(?])n#dThe value depends on two variable, n and d, and so you may
create a dyadic verb, focusing attention on functions rather than on
variables.
n( 4 : 'x>+:(?]) x#y')d
or, using tacit code:
n([>[:+:[:(?])#)d
Your questions:
1) how do I avoid @ especially once we remove explicit arguments?
- by using cap. ([:)
4) Is there a good way to have named variables (ie. avoid getx, gety)?
replace
getx =: 0{ ]
gety =: 1{ ]
revDom =: getx *. +./ @ (gety # [)
with
revDom =: (0{ ]) *. +./ @ ((1{ ]) # [)
5) Why is a hook the default and not composition?
- Because J'ers love hooks! For composition use the capped fork ([: f g)
-Bo
>________________________________
> Fra: Michal D. <[email protected]>
>Til: [email protected]
>Sendt: 6:01 fredag den 2. november 2012
>Emne: [Jprogramming] Arc consistency in J
>
>Hi All,
>
>I've managed to write my first not-completely-trivial program in J. It
>implements an arc consistency algorithm (
>http://en.wikipedia.org/wiki/Local_consistency#Arc_consistency). I
>would appreciate any comments regarding style, what I'm doing wrong in
>J or how to improve the code. I also have a couple of questions of my own:
>
>1) how do I avoid @ especially once we remove explicit arguments?
>2) how do I avoid constant boxing/unboxing due to fill (see arcsX)?
>3) Is a boxed value always a pointer? One could imagine implementing
>'ragged' arrays without pointers.
>4) Is there a good way to have named variables (ie. avoid getx, gety)?
>5) Why is a hook the default and not composition?
>
>Code at: http://pastebin.com/k4XuKfFi
>
>Cheers!
>
>Mike
>----------------------------------------------------------------------
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>
>
>
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