; has two kinds of behaviors.

One kind of behavior is evident when dealing with sentences where the
supplied nouns are unboxed:

   1;2;3
+-+-+-+
|1|2|3|
+-+-+-+

The other kind of behavior is evident when dealing with sentences
where the supplied nouns are boxed:

   a:;a:;a:
+--+--++
|++|++||
||||||||
|++|++||
+--+--++

From a high level point of view, the rightmost element gets special
treatment when it is already boxed.

From a low level point of view, the rightmost element gets special
treatment when it is unboxed.

This distinction exists because of the structure of J's expression
grammar. http://www.jsoftware.com/help/dictionary/dicte.htm

In some ways, this issue is analogous to the distinction between a
dotted pair and a normal list element in LISP (except, of course, J
does not have cons cells -- dyadic verb definitions roughly occupy
that role in the language).

FYI,

-- 
Raul

On Fri, Jun 1, 2012 at 8:46 AM, Steven Taylor <tayl...@gmail.com> wrote:
> "Oh, that's the asymmetry of ; again!"
>
> I should have realised!  Oops.  I was pleased to find that a: worked when I
> tried it.  Didn't see that in any of the documentation that I looked at.
>
> thanks,
> -Steven
>
> On 1 June 2012 12:55, Brian Schott <schott.br...@gmail.com> wrote:
>
>> Bob (and Henry, of course),
>>
>> That is a terrific explanation. Thanx to both of you.
>>
>> On Fri, Jun 1, 2012 at 1:49 AM, bob therriault <bobtherria...@mac.com>
>> wrote:
>> > Hi Steven,
>> >
>> > If we aren't at the outer limits, you can see them from here :)
>> >
>> > The different levels of boxing actually have different selection
>> methods. The best explanation I have seen is Henry Rich's "J for C
>> Programmers - Chapter 17"
>> http://www.jsoftware.com/help/jforc/more_verbs_for_boxes.htm#_Toc191734399
>> >
>> > Hope this helps.
>> >
>> > Cheers, bob
>> >
>>
>>
>> --
>> (B=)
>> ----------------------------------------------------------------------
>> 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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