I prefer 0=⎕io, especially for array arithmetic, because it works
well for mixed-radix indexing, which is essential for array operations.
As an implementor of functional array language processors (compilers
and interpreters), I do this sort of thing a lot, under the covers.
Consider this nice identity, in which base value (#.) and
representation (#:)
are inverses, when we operate in origin zero:
i. 8
0 1 2 3 4 5 6 7
2 #. 2 2 2 #: i. 8
0 1 2 3 4 5 6 7
Now, let's do it with origin one:
2 #. 2 2 2 #: 1 + i. 8
1 2 3 4 5 6 7 0
That's nice, except the expression is no longer an identity. For those
who don't care
about getting correct answers, this is fine. However, I have clients who
do care about such things.
Now, back to FORTRAN/Fortran: An array can have an arbitrary index origin.
Worse yet, EACH array in a program can have its own, unique, index origin.
Let's ignore mathematics for a moment, and contemplate how much
you would like to be handed a large system to maintain,
in which the author exercised this Awesome Power. It may be possible
to maintain, but it (a) is not fun, and (b) it introduces a rich set of ways
to generate faulty programs.
Not for me, thanks.
Bob
On 2018-05-18 10:40 AM, Don Guinn wrote:
If you look at the notation for vectors and matrices in mathematics the
first element of a vector is written as V(1) and the upper left corner of a
matrix is M(1,1). Having to use parens because I can't figure out how to
put subscripts in e-mail.
True, in summations of infinite series etc. the lower limit is chosen that
makes the most sense and can be any value. But when the index has no
significance except to choose elements of a vector or matrix it starts with
one in the all math texts I can find.
This may change as now that so many people program and are used to an index
origin of zero. My point was not what the index origin should be when it is
only used to locate a element. One works well as does zero. The mistake in
APL was to duck the issue by allowing both making generalized indexing
difficult.
On Fri, May 18, 2018 at 5:19 AM, alexgian via Chat <[email protected]>
wrote:
OK, I'll give the questions a go, too, bearing in mind that I am not a
power user, just a J dilettante.
How similar? - About as similar as Lua and Javascript :) !!! They may
look completely different on the surface and are used differently but the
underlying ideas and the paradigm (mindset required) are practically
identical.
Re EBCDIC - Don't really know, but as someone (Don?) already said, EBCDIC
was no remedy in that case either. Anyways motivation-wise the character
set was probably quite low in priority.
Can they do the same things? - Er hm, get the same results? Yes. The
same way? Not quite, only sometimes. Plus, I don't think APL has implicit
functions. (Correct me if I'm wrong)
Typing - You're kidding, right?
OOP - No idea about modern APLs. J has a way of doing it, but every time
I tried using it I ended up swearing. Good job I don't do
programming-in-the-large in J. I'm sure you could get used to the system
though, just not sure if you would like it. Stick to Java if you want
traditional OOP, you could always call J from a library, I suppose.
Supersets - Already answered I think. Once, perhaps. No more, due to
progress.
Niche - Depends on your niche. I suspect their importance is quite high
in the refined realms of the big players, math quants and such. So
definitely not "niche" economically.
I have to say, I mainly write in Clojure or Scheme but I often see the J
style of thinking creeping in. Which I like!
On 17 May 2018 at 04:27 jane dalley <[email protected]> wrote:
This is my first post; my hope is this is an appropriate question.
My knowledge of APL and J is very limited so my expectation is a simple
answer that is within my limited ability to grasp.
Examples:
How similar are both APL and J?
To the best of my recollection APL could be written with EBCDIC so why J?
Can APL do everything J can do and visa versa?
Can APL and J be forced to be strongly typed?
Are APL and J capable of being Object Oriented like C++ or C#?
Would one view J as a superset of APL?
Are J and APL more than niche languages?
Sorry if any of these questions are perceived to be offensive, probably
they have been asked many times before.
Sorry also if these questions are deemed silly such as a toddler might
ask.
Regards,
Jane the novice of J
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Robert Bernecky
Snake Island Research Inc
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