This actually looks like a good idea. I was concerned about
performance, but this kind of thing also seems just as fast as the
other approach, and a bit more compact:
num=:(1 [ 0+{.@,) ::0:
numeric=: 0 = 0 {.@{. ,
1e4 timespacex 'numeric 3 4'
1.0472e_6 2176
1e4 timespacex 'num 3 4'
9.204e_7 1408
Plus, we don't have to worry about if sparse array default value will
ever leak in, in some J version.
Thanks,
--
Raul
On Thu, Nov 9, 2017 at 1:40 PM, Marshall Lochbaum <mwlochb...@gmail.com> wrote:
> Actually, the domain error thing gives me an idea:
>
> numeric =: (1[[:+''($,)]) :: 0:
>
> numeric i.3 5
> 1
> numeric <2 3
> 0
> numeric 'abcd'
> 0
>
> Reshape to scalar, attempt to apply complex conjugate, and then return
> 1. If conjugate failed, return 0. You could skip the reshape, yielding
> ((1[+) :: 0:), but this gives a false positive on empty character arrays
> and will actually compute the conjugate of a complex argument, which
> could be slow.
>
> Marshall
>
> On Thu, Nov 09, 2017 at 01:01:40PM -0500, Raul Miller wrote:
>> I would be inclined to do something similar:
>>
>> numeric=: 0 = 0 {.@{. ,
>>
>> That said, it's usually sufficient to rely on domain errors for this
>> kind of thing.
>>
>> Thanks,
>>
>> --
>> Raul
>>
>>
>>
>>
>>
>>
>> On Thu, Nov 9, 2017 at 12:20 PM, Michael Berry <mjabe...@gmail.com> wrote:
>> > Hello J world,
>> >
>> > I have a verb that returns scalar 1 if the argument is numeric of any shape
>> > and scalar 0 otherwise.
>> > It works fine:
>> >
>> > numeric i. 5
>> >
>> > 1
>> >
>> > numeric 9
>> >
>> > 1
>> >
>> > numeric i. 2 3 4
>> >
>> > 1
>> >
>> > numeric 'cat'
>> >
>> > 0
>> >
>> > numeric 3#<i. 4
>> >
>> > 0
>> >
>> >
>> > My definition feels clumsy, however. Can anyone suggest something nicer?
>> >
>> >
>> > numeric=: monad : '0 -: 0{ , 1{. 0#y'
>> >
>> >
>> > -Michael
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