Newsgroups: comp.lang.apl
Path: utzoo!utgpu!news-server.csri.toronto.edu!torsqnt!jtsv16!blister!itcyyz!yrloc!hui
From: hui@yrloc.ipsa.reuter.COM (Roger Hui)
Subject: Re: Statistical Functions in J
Message-ID: <1991May31.171148.12753@yrloc.ipsa.reuter.COM>
Reply-To: hui@yrloc.ipsa.reuter.COM (Roger Hui)
Organization: Iverson Software Inc.
References: <1991May12.145907.19563@yrloc.ipsa.reuter.COM> <356@tslwat.UUCP> <1991May21.042804.21102@yrloc.ipsa.reuter.COM> <414@tslwat.UUCP> <1991May29.191441.1279@aplcen.apl.jhu.edu> <1991May29.204803.26927@jato.jpl.nasa.gov>
Date: Fri, 31 May 91 17:11:48 GMT

Dave Weintraub writes:
 
> I fully agree.  This is the path taken by IBM with APL2: write external
> functions (in Assembler, FORTRAN, PL/I,  C, ...) and make these available
> using QuadNA.
 
Dave, this is in fact possible with LinkJ.  LinkJ permits calling
J from C and C from J.  C functions so introduced behave like primitive
verbs, in the sense that they may be assigned names, and (independently)
may serve as arguments to adverbs and conjunctions.  For example,
 
   f =. 10!:57     NB. f is an external function encoded by 57
   f"r y           NB. Apply f to rank r cells of y
   x f"r y         NB. Apply f to rank r cells of x and y
   f/y             NB. f insertion ("reduction")
   x f/y           NB. f table ("outer product")
   10!:362"r y     NB. Apply the external fn encoded by 362 to rank r cells
 
 
Sam Sirlin writes:
 
> An interesting path in this vein is the path taken by ProMatlab. It uses the
> dynamic linking capabilities of modern machines. Hence a variety of compiled
> routines are available (and more can be written by the user) that are easily
> linked in while running the Matlab interpreter,  ...
 
Sam, this is possible with LinkJ on systems supporting dynamic linking.
 
 
Lou Kates writes:
 
> >I am puzzled.  How would a belief in regression and projection
> >instead of expectation as the key concept materially affect
> >the design of the primitives m., n., and s.?
>                    ^^^^^^^^^^
> When everything you can think of gets put into the lanugage its hard
> to see how they all qualify as primitive.
>   ...
> I guess its whether you believe in parsimony or not.
>
> Personally I   would   rather have   a wider  family of  powerful
> operations at my disposal (such as regression, constrained linear
> optimization a la simplex  or Karmarker, eigenvalue calculations,
> etc.) that are not easily derivable from each other rather than a
> large  set  of functions which are all readily derivable from the
> ideas of regression  and   projection.  My own preference, and  I
> suspect that of many others too, would be  that if   you feel the
> need to  have zillions of functions at  your  disposal,  define a
> standard library so that you can take them out of the language so
> as to keep  the   language  smaller  and more    manageable.
>   ...
 
It may be helpful to consult your copy of the Dictionary.  In it,
you'd find that (a) not everything you can think of is in the language;
(b) we do not in fact have zillions of functions in the language;
(c) the ISO APL %. (matrix inverse and matrix divide, what you called
regression) is in the language; (d) characteristic values and vectors
are in the language.
 
Many primitives can be derived readily from each other.  One could
argue that *: (nand) makes the other boolean functions redundant, as do
- (minus) and % (divide) for + (plus) and * (times).  Similarly, one can
derive |. (reverse), |: (transpose), u;.n (cut), u . v (generalized
determinant), %. (domino), and so forth, from { (from).
 
There is more to parsimony than reducing the number of primitives.

-----------------------------------------------------------------
Roger Hui
Iverson Software Inc., 33 Major Street, Toronto, Ontario  M5S 2K9
(416) 925 6096