I just now realized that (as often seems to happen with J) there are at
least two other ways to compute all combinations of 3 (or x) elements from a
set of six (or y) elements. (This computation was used in my previous post
"A viewmat phrase to display all 216 web-safe colors" to compute argument x
to dyad viewmat.)
So instead of the phrase provided in the previous post for displaying 216
web-safe colors:
(51 * (6 (&#.)(^:_1) i. 216)) viewmat 12 18 i. 216
Either of the two following equivalent (possibly simpler) phrases could also
be used, the first using "Antibase" ( #: ) and the second using "Catalogue"
or "Cartesian Product" ( } ):
(51 * 6 6 6 #: i. 216) viewmat 12 18 $ i. 216
(51 * > , { (i. 6);(i. 6);(i. 6)) viewmat 12 18 $ i. 216
+++
That previous post computed the base x representation of decimal number
using the dyad:
(&#.)(^:_1)
defined here:
http://www.jsoftware.com/help/phrases/representations.htm
For example, the previous post computed the base 6 representation of the
numbers from 0 to 215 as follows:
6 (&#.)(^:_1) i. 216
However, I now see there are a couple of (possibly simpler) alternative
phrases.
+++
(1) One alternative uses "Unbox" on "Enfile" on "Catalogue" or "Cartesian
Product":
> , { (i. 6);(i. 6);(i. 6)
"Catalog" and "Cartesian Product" are defined here:
http://www.jsoftware.com/help/dictionary/d520.htm
As a side note - I am curious if there is a more compact way of representing
the repetitive phrase:
(i. 6);(i. 6);(i. 6)
I have tried fiddling with tacking combinations of the adverbs ~ and / and
^:3 onto the verb ; ... but no luck.
+++
(2) Another alternative uses "Antibase":
6 6 6 #: i. 216
defined here:
PDF!
http://www.jsoftware.com/jwiki/HenryRich?action=AttachFile&do=get&target=J602_RefCard_color_letter_current.pdf
+++
Upon first reading, it wasn't clear to me from the definition of dyad
Antibase provided in the Vocabulary here:
http://www.jsoftware.com/help/dictionary/d402.htm
that its x argument could be an integer array each of whose elements is the
desired base. But the example for "Antibase" in the above PDF from Henry
Rich made it clear how to do this.
+++ +++ +++
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
