2 things:
a) how about qualifying the behaviour of u with !. ?
In the absence of !. , return a domain error where called for;
However, (%!.c m. 10 (2)) for some number c would return c wherever appropriate
in the resulting array. Similarly for dyadic % and ^ .
b) It appears that n in {x} (u m. n ) y must always be scalar. Is there a
possibility of
allowing n's shape to conform with y (say) with the usual rules for arguments
of
different rank?
Mike
Sent from my iPad
> On 28 Apr 2023, at 13:00, Henry Rich <[email protected]> wrote:
>
> I am OK with (0 % m. n 0)'s giving 0, in accordance with J's properties of
> 0. (0 ^ m. n 0) should likewise give 1.
>
> (% m. n 0) is a different case. Should it return _? Can it be good design
> to have a primitive whose whole purpose is to confine its range, and then
> have it give a result that is out of range? Worse than that, a result that
> loses precision on integers and requires conversions? I don't see analogy to
> the real numbers as a sufficient argument; and the fact that _ is not a
> number is particularly important when the range is integers. Domain error
> seems the better solution, pending further discussion.
>
> (% m. 10 (2)) seems to me different altogether. Domain error is the best way
> for the user to handle these exceptions.
>
> BTW, in earlier J versions u :: v was pretty slow when u failed: the code
> prepared for debugging, allocating blocks and formatting error messages. As
> of J9.4 u :: v transfers directly to v when u fails, with low overhead.
>
> Henry Rich
>
>> On 4/27/2023 3:16 PM, Raul Miller wrote:
>> Hmm...
>>
>> Looking at this, the domain errors do seem analogous to divide by zero
>> errors.
>>
>> So, in the context of %m.n, if we were being purely symmetric, a 0
>> result when both the numerator and denominator were effectively 0
>> would be the way to go, with an infinite result for the remaining
>> cases. (Infinity in modulo arithmetic seems a bit awkward, but I don't
>> have any better suggestions there.)
>>
>> And, I suppose similar thinking might hold for monads?
>>
>> Thanks,
>>
>
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