Exactly -I agree that the NaN result is quite satisfactory .It explains
the problem better than the ff verb that gives a 1. That is the reason
for the "why"
The ff verb does give a switch -if the result is 1 then do something
else. However returning 1 is not a sure way to differentiate between a
NaN and 10%10
However using
NaN'= __ %__ gives an error
so it can't be used as a switch
In the old days, an infinite or unreal result generally meant a lot of
kludging of programs to avoid this. (if divisor =0 do something else).
Don
On 11/19/2015 5:07 AM, Henry Rich wrote:
Why NOT NaN? What else? _ embraces numbers of vastly different
sizes. aleph-0%aleph-1 is 0, aleph-1%aleph-0 is _, and (who knows?)
there could be values in between. Here NaN means 'unknown'. In other
cases it means 'unrepresentable'.
The standard specifies a number of operations that generate NaN:
https://en.wikipedia.org/wiki/NaN#Operations_generating_NaN
J treats some of these, but not all, as NaNs.
Henry Rich
On 11/19/2015 1:11 AM, Don Kelly wrote:
How is this "why" ? it appears that all it does is substitute a
number (in this case 1) rather than have NaN. I can see this as a
way to avoid a NaN error by flagging it without stopping execution.-
not as an explanation for the NaN using __%__
*ff=: % :: 9:*
__ ff __
9
3 ff 2
1.5
also works with
*ff2=: - :: 9:*
__ ff2 __
9
4 ff2 1
3
Don
On 11/18/2015 8:28 PM, Linda A Alvord wrote:
Here's why...
f=:0:@% ::1:
_ f _
Linda
1
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Raul
Miller
Sent: Monday, November 16, 2015 1:46 PM
To: Programming forum
Subject: Re: [Jprogramming] Why is subtraction and division of
rational numbers so hard?
You might also like to see:
L=:(-_),(-2%~1-~%:5),0,(2%~1-~%:5),_
0:@% ::1:"0/~ L
1 0 0 0 1
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
1 0 0 0 1
Thanks,
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