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Re: [Bug-apl] How does a vector become a matrix?


From: David B. Lamkins
Subject: Re: [Bug-apl] How does a vector become a matrix?
Date: Mon, 12 May 2014 10:31:46 -0700

Perhaps "Principles of APL 2" by Dr. James A. Brown (the "inventor"[*]
of APL 2) will shed some light on the behaviors you're seeing.

http://www.softwarepreservation.org/projects/apl/Papers/PRINCIPLESOFAPL2/view

The entire document is worth reading, as it explains how and why APL 2
differs from APL.

Chapters 11 through 15 are particularly apropos to our current
discussion regarding enclosures and empty arrays.

Point is: APL 2's rules may be counterintuitive to those of us coming to
APL 2 from APL. (I know I've struggled mightily with the learning APL 2,
despite having been a rather accomplished APL programmer.)
Counterintuitiveness, though, does not equate to arbitrariness.



[*] Dr. Brown built upon the work of Dr. Trenchard More.

Unfortunately, most of Dr. More's papers are behind paywalls. A look at
the abstracts of his papers, though, ought to dispel the notion of
arbitrariness w.r.t. the underlying theory of nested arrays.

http://en.wikipedia.org/wiki/Trenchard_More

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5391380&url=http%
3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F5288520%2F5391374%2F05391380.pdf%
3Farnumber%3D5391380


There are others exploring nested arrays. This dissertation, for
example, includes a survey of some of the research in the field:

ftp://ftp.cs.joensuu.fi/pub/Dissertations/eriksson.pdf



On Mon, 2014-05-12 at 11:04 -0500, Blake McBride wrote:
> One can make up a set of, perhaps arbitrary, rules, and apply them
> consistently only to end up with something unintelligible and
> difficult to use.  Enclose "turns into a scalar" rather than enclose
> "adds a level of boxing" is the perfect example.
> 
> 
> I programmed in APL for five years.  Not having access to APL2, I
> wrote my own equivalent of boxing and unboxing functions in plain APL
> that were very, very useful.  I'm sure my functions were slow.  I was
> looking forward to native and fast support for the same capabilities.
>  If I can find APL2 idioms to do the same thing (simple and uniform
> boxing and unboxing) as I asked in my previous email to Jürgen, I
> would be happy indeed.






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