[Jprogramming] Bracket APL-to-J question

[Roy A. Crabtree]

Agreed.

Doesn't it work in both IOs?

On Sat, Jun 14, 2008 at 2:36 PM, Ralph G Selfridge <selfrid at cns.ufl.edu>
wrote:

> Yes it is, remember J is origin 0. [-.5] puts things together with a new
> leading axis. If origin is 1 (APL) you would then use [.5]
>
>
>
>
> On Sat, 14 Jun 2008, Randy MacDonald wrote:
>
>  No, it isn't.
>>
>> Roger Hui wrote:
>>
>>> x,[_0.5] y in APL is equivalent to x,:y in J.
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: PackRat <packrat at anet.com>
>>> Date: Thursday, June 12, 2008 6:11
>>> Subject: [Jprogramming] Bracket APL-to-J question
>>> To: Programming forum <programming at jsoftware.com>
>>>
>>>
>>>  I wasn't sure which forum was the best for this kind of APL-to-J
>>>> programming question, so I thought I'd try it here.  If that's not correct,
>>>> please let me know, so that I can submit any future questions along this
>>>> line to the appropriate forum.
>>>>
>>>> I have a master's degree in music, and one of the main reasons behind my
>>>> learning J is to translate a published set of 66 computer-
>>>> assisted musical composition functions from APL to J.  I'm pleasantly
>>>> surprised that my intense trying over the past several months to understand
>>>> array programming and J in particular seems to be paying off. Though by no
>>>> means being anywhere near very knowledgeable, I've been able to look at both
>>>> J and APL code and, in most cases, to understand what was going on and, with
>>>> APL code, to successfully begin translating to J versions.  (I've even been
>>>> able to note on occasion that J had a better/shorter way to do something
>>>> than the APL code did.)
>>>>
>>>> However, I ran into an APL construction that I cannot find in the half
>>>> dozen APL books I have.  Since many/most of you have APL background, I
>>>> thought I ask here so that I could have some assistance in translating to J.
>>>>  Here's the line that's stumped me (I substituted J's ~: for the APL
>>>> not-equal symbol and <- for APL's assignment symbol):
>>>>
>>>>   Z <- R,[_0.5](0 ~: ATTK)/ATTK <- +/[0] Z
>>>>
>>>> I understand everything except the [_0.5] code and what it means in
>>>> context.  It doesn't seem to fit anything in my books about bracketed
>>>> indexing in APL, and none of the book indexes lead to any information about
>>>> what this construction might mean, so that I can translate it to J. Thanks
>>>> in advance for any help!
>>>>
>>>>  ----------------------------------------------------------------------
>>> For information about J forums see http://www.jsoftware.com/forums.htm
>>>
>>>
>>>
>> --
>> ------------------------------------------------------------------------
>> |\/| Randy A MacDonald       | APL: If you can say it, it's done.. (ram)
>> |/\| ramacd <at> nbnet.nb.ca |
>> |\ |                         | The only real problem with APL is that
>> BSc(Math) UNBF'83            | it is "still ahead of its time."
>> Sapere Aude                  |     - Morten Kromberg
>> Natural Born APL'er          |
>> -----------------------------------------------------(INTP)----{ gnat }-
>>
>>
>> ----------------------------------------------------------------------
>> 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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