Jan-Pieter,
Thank you for the solution. I’m a huge tacit fan (or maybe the word is
“dilettante”) when writing J…less so when reading it a week later :-). In this
particular case the tacit solution wins on elegance and (at least at the
moment) seems perfectly clear.
Thanks again.
Ed
Sent from my iPad
> On Oct 21, 2022, at 1:55 PM, Jan-Pieter Jacobs <janpieter.jac...@gmail.com>
> wrote:
>
> I don't know whether you'r only looking for a tacit function, but this
> would also likely work if fold is unavailable for you (untested):
>
> {{ for_val. y do. if. f val do. val_index{y return. end. end.}} coords
>
> Jan-Pieter
>
>> On Fri, 21 Oct 2022, 19:51 Ed Gottsman, <edward.j.gotts...@gmail.com> wrote:
>>
>> Pascal,
>>
>> Your original solution is perfect for me—I don’t happen to need the
>> index. And there may in fact be no items with f = 1.
>>
>> Very clever: it gets a place of honor in the flashcard deck :-).
>>
>> Many thanks.
>>
>> Ed
>>
>> Sent from my iPad
>>
>>> On Oct 21, 2022, at 12:46 PM, 'Pascal Jasmin' via Programming <
>> programm...@jsoftware.com> wrote:
>>>
>>> if you want the index rather than the coordinate values, then
>>>
>>> (1 i.~ f) y
>>>
>>> will "short circuit" to the first 1
>>>
>>> and
>>>
>>> ({~ 1 i.~ f)
>>>
>>> may be faster to get first coordinates than my original solution, though
>> errors if there are no items with 1 = f
>>>
>>>
>>>
>>>
>>> On Friday, October 21, 2022 at 12:55:41 p.m. EDT, 'Pascal Jasmin' via
>> Programming <programm...@jsoftware.com> wrote:
>>>
>>>
>>>
>>>
>>>
>>> }.^:(0 = f@{.)^:_
>>>
>>> will return the list with the head being the first f not equal 0.
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Friday, October 21, 2022 at 12:19:41 p.m. EDT, Ed Gottsman <
>> edward.j.gotts...@gmail.com> wrote:
>>>
>>>
>>>
>>>
>>>
>>> Hi. I’m blanking on something basic and research isn’t helping. When
>> the blindingly obvious solution is revealed I will blame a combination of
>> sleep deprivation and senescence.
>>>
>>> I’ve got a long list of coordinates ordered by desirability. I want to
>> invoke f (a custom script) with each coordinate in turn. f may return 0
>> (failure), in which case I want to invoke it again with the next
>> coordinate. When f (eventually) returns 1, I want to terminate—the
>> remainder of the coordinates should not be processed. (Note that the very
>> first invocation of f may return 1.)
>>>
>>> This *almost* feels like ^: in its Do While form. Almost. It also
>> feels like SCs around list operations (though they seem to be limited to
>> primitives).
>>>
>>> Help.
>>>
>>> Many thanks.
>>>
>>> Ed
>>>
>>> Sent from my iPad
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