Yes. I would be implementing
([ -.!.0 -.)
but I don't want to demand that the user write that. It's like
(i. <./) y
which is implemented as (i.!.0 <./) y
Henry Rich
On 4/25/2021 12:41 PM, Roger Hui wrote:
A friendly reminder: beware of tolerant comparison when dealing with the
set functions. In particular, the meme (i.@# = i.~) for computing the
nubsieve and nub, in the APL folklore for decades, can give bad results for
floating point arguments with tolerant comparison.
If this idea is new to you, the following may be helpful:
*- Index-Of on Multiple Floats
<https://www.dyalog.com/uploads/conference/dyalog17/presentations/D07_IndexOf_on_Multiple_Floats.zip>*,
Dyalog User Meeting, 2017
*- Tolerant Unique
<https://www.dyalog.com/uploads/conference/dyalog17/presentations/D10_Tolerant_Unique.zip>*,
Dyalog User Meeting, 2017.
On Sun, Apr 25, 2021 at 9:06 AM Henry Rich <[email protected]> wrote:
The i.-family is missing a member, I think. We have (x -. y) to find the
items of x not in y, but we don't have a way, supported by fast code, to
find the items of x that ARE in y. I'd like to fill that in. But what
is the best idiom, call it I? I have two requirements, apart from valid
result:
* the definition should allow for precomputing the search table via at
least one of m&I and I&n
* the definition should give reasonable and explainable results when x
and y have different rank
In addition, it would be nice if
* repeated items in one argument, preferably x, are repeated in the
result, for symmetry with (x -. y)
I have used two idioms for intersection: ([ -. -.) and (e. # [) . (e. #
[) is ill-behaved on arguments of different rank. So I am leaning toward
([ -. -.)
for I . Any other ideas?
Henry Rich
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