Actually I was thinking of plain trig, cartesian coordinates, where the
tangent of an angle is the ratio of the x coordinate to the y
coordinate, both real. Of course in an expression like 1j2, 1 and 2 are
both real, so maybe I am beating a dead horse. It might be nice if j
were to return atan2 when asked for the arctangent of a rational, but it
is of but small moment to me.
Randy MacDonald wrote:
Hello Eldon;
So, the "r" should be a "j" ... I'm not so confused.
------------------------------------------------------------------------
|\/| Randy A MacDonald | APL: If you can say it, it's done.. (ram)
|/\| [EMAIL PROTECTED] |
|\ | |If you cannot describe what you are doing
BSc(Math) UNBF'83 þas a process, you don't know what you're doing.
Sapere Aude | - W. E. Deming
Natural Born APL'er | Demo website: http://156.34.82.232/
-----------------------------------------------------(INTP)----{ gnat }-
----- Original Message ----- From: "Eldon Eller" <[EMAIL PROTECTED]>
To: "General forum" <[email protected]>
Sent: Friday, June 30, 2006 12:21 AM
Subject: Re: [Jgeneral] significant digits
What I mean is:
(-1,1)
* |
\ |
\ |
-----------------------
| \
| \
| *
(1,-1)
Randy MacDonald wrote:
Hello Eldon;
Do you mean:
_3 o. _1r1
_0.785398
_3 o. 1r_1
_0.785398
(_3 o. 1r_1) = _3 o. _1r1
1
I must be missing something, or reading the vocabulary pages
incorrectly.
------------------------------------------------------------------------
|\/| Randy A MacDonald | APL: If you can say it, it's done.. (ram)
|/\| [EMAIL PROTECTED] |
|\ | |If you cannot describe what you are doing
BSc(Math) UNBF'83 þas a process, you don't know what you're
doing.
Sapere Aude | - W. E. Deming
Natural Born APL'er | Demo website: http://156.34.73.214/
-----------------------------------------------------(INTP)----{
gnat }-
----- Original Message ----- From: "Eldon Eller" <[EMAIL PROTECTED]>
To: "General forum" <[email protected]>
Sent: Thursday, June 29, 2006 3:14 PM
Subject: Re: [Jgeneral] significant digits
The arc tangent of _1r1 is different from the arc tangent of 1r_1.
Randy MacDonald wrote:
Donna;
Your posts, while articulate, seem to be veering off into meta-land.
If your original question was:
What is the difference between
1r3
and
111r333
all I can say is they produce the same result when evaluated, but
each use a different number of keystrokes.
If your question was something else, I apologize for my lack of
proper attention.
I'm thinking this is different in the case of 1 and 1.1-.1, where
1 = 1.1 - .1
but
([]dr 1){ne}[]dr 1.1-.1
NB. Excuse the APL, I'm being lazy in not looking up the foreign
for data representation.
(J-note)
1.1-.1
1.1
was something I had to think about for a bit. Definitely a gotcha.
------------------------------------------------------------------------
|\/| Randy A MacDonald | APL: If you can say it, it's done.. (ram)
|/\| [EMAIL PROTECTED] |
|\ | |If you cannot describe what you are doing
BSc(Math) UNBF'83 þas a process, you don't know what you're
doing.
Sapere Aude | - W. E. Deming
Natural Born APL'er | Demo website: http://156.34.71.130/
-----------------------------------------------------(INTP)----{
gnat }-
----- Original Message ----- From: "dly" <[EMAIL PROTECTED]>
To: "General forum" <[email protected]>
Sent: Wednesday, June 28, 2006 6:54 PM
Subject: Re: [Jgeneral] significant digits
Yes I do not see how my statement that I do not expect J to
resolve these problems differs from your statement that it is a
programming issue and not a language issue.
I merely observe that when one person considered something noise,
it may not actually meet the definition of noise and may actually
represent a loss of information. Obviously it is information not
interesting to everyone.
I do not grasp why you do not see why I am interested in knowing
the precision of J before I use it because I think it is somewhat
analogous to you needing to know the precision of a program I
produced before you called on it as a subroutine.
What is and is not built in varies by language. There is much
built in to J that was not built in to APL. There may or not be
other languages that have things built in to them that are not
built in to J. This is all that I am trying to discover.
In my experience such a process of discovery could be aided by
others who are expert with the language one is trying to explore
rather than deferring to such time as you my or may not become an
expert yourself and such information can be used in decision
making. In some cases however there may be no one with the time
or inclination to share such information.
Thanks
Donna
[EMAIL PROTECTED]
On 28-Jun-06, at 9:39 PM, John Randall wrote:
dly wrote:
I am not expecting J to resolve these problems I a merely
trying to
ascertain how J has improved from APL and to know its limitations
before thinking of applying it to some problems.
Donna:
In my opinion, what you are getting at is a programming issue,
not a
language issue.
All languages can easily represent rational numbers as
canonicalized pairs
of integers: J happens to have them built-in. If you need to
deal with
non canonicalized pairs, it is easy to do that too, although
this is not
built-in in J.
The matrix similarity questions I mentioned needs the programmer
to keep
in mind the ring over which the similarity is being
constructed. I do not
see how the language is going to do that for you.
Best wishes,
John
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