Re trying my own examples—
I’m not too proud to flaunt my ignorance:
foo=:[x] ".@'name' y
|domain error
| foo=:[x] ".@'name'y
I long ago choose (probably foolishly) to not spend a lot of time trying to
understand tacit J. My rationale was that I would be unlikely to recover the
cycles lost to the idle loop while I was studying to improve my j code. You
know the old wisdom:
Q: When should you optimize your code?
A: Not yet.
Yet, now that I have been retired for a few years, I have the curiosity to try
again. Thanks to JforC, I am learning that [ and ] appear often in tacit
expressions, but x not so much. I expect that with a few more readings of
Forks, Hooks, and Compound Adverbs I’ll see how dumb my confusion was.
Your examples should help; thanks Raul!
> On Aug 24, 2018, at 10:18 AM, Raul Miller <rauldmil...@gmail.com> wrote:
>
> Sort of?
>
> It's an optional left argument that would be part of the larger J
> expression if it was present?
>
> (That phrase was intended to show how it's used...)
>
> Stil, we should have more havbits of trying things out.
>
> With that in mind:
>
> example=: p:i.3
> 9 */@(".@'example') 8
> 30
> */@(".@'example') 8
> 30
> */@(".@'example')
> */@(".@example)
>
> It's better though, when you try your own examples.
>
> Thanks,
>
> --
> Raul
>
> On Fri, Aug 24, 2018 at 9:27 AM 'Jim Russell' via Programming
> <programm...@jsoftware.com> wrote:
>>
>> Is it safe to understand that “[x]” indicates an optional left argument, and
>> is not part of a the J expression?
>>
>>> On Aug 24, 2018, at 9:19 AM, Raul Miller <rauldmil...@gmail.com> wrote:
>>>
>>> Also, in this example, ‘name’ was meant to represent a pronoun.
>>>
>>> Thanks,
>>>
>>> —
>>> Raul
>>>
>>>> On Friday, August 24, 2018, Henry Rich <henryhr...@gmail.com> wrote:
>>>>
>>>> ".@'name' is a verb. In
>>>>
>>>> [x] ".@'name' y
>>>>
>>>> y (and x if given) are ignored, and the result is the value of (name) when
>>>> the verb is executed.
>>>>
>>>> This is the same as it used to be, but is now faster.
>>>>
>>>> Henry Rich
>>>>
>>>>> On 8/23/2018 10:22 PM, Brian Schott wrote:
>>>>>
>>>>> Henry, I'm still a little lost.
>>>>> Is the final `npixels` a (monadic, in this case) verb which will take a
>>>>> noun argument,
>>>>> or is the current value of windowsize that noun.
>>>>>
>>>>> If the latter, and windowsize is that noun, then what is the value of y in
>>>>> the original expression `[x] ".@'name' y`?
>>>>>
>>>>> If the former (`npixels` is a verb -- and this is the one I'm leaning
>>>>> toward), then what is the y value that is its argument?
>>>>>
>>>>> TIA.
>>>>>
>>>>> On Thu, Aug 23, 2018 at 9:41 PM, Henry Rich <henryhr...@gmail.com> wrote:
>>>>>
>>>>> Often you need for a verb to refer to the value of a name when the noun is
>>>>>> executed, rather than when it is defined. So, rather than
>>>>>>
>>>>>> npixels =: */ windowsize
>>>>>>
>>>>>> which would just be a noun, you write
>>>>>>
>>>>>> npixels =: 3 : '*/ windowsize'
>>>>>>
>>>>>> to defer taking the value of (windowsize) until (npixels) is executed.
>>>>>>
>>>>>> In tacit code, you used to write
>>>>>>
>>>>>> npixels =: */ @: ". @ ('windowsize'"_)
>>>>>>
>>>>>> to get the same result. Recently the syntax was added to allow
>>>>>>
>>>>>> npixels =: */ @: ". @ 'windowsize'
>>>>>>
>>>>>> All that still works. But the (".) verb starts the parser and executes
>>>>>> its y argument as a sentence, with a modest overhead that will matter if
>>>>>> the verbs have small ranks. Now, you can write
>>>>>>
>>>>>> npixels =: */ @: (". @ 'windowsize')
>>>>>>
>>>>>> [parentheses important! make sure you see why]. When (npixels) is
>>>>>> defined, this form will detect that the argument to (".) is a single
>>>>>> name.
>>>>>> When (npixels) is executed, the name will be evaluated without going
>>>>>> through the overhead of starting a sentence.
>>>>>>
>>>>>> Henry Rich
>>>>>>
>>>>>> ----------------------------------------------------------------------
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>>>>>
>>>>
>>>>
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