Jose/Pepe has done this. afaiu I think it is a way to avoid unnecessary
intermediate names.
I can't say I understand how adding 1: 0 to the f. result changes how $:
applying to its entire new verb phrase "complications" gets avoided in any way.
, 1 : ' u@cut f.'
On Wednesday, February 9, 2022, 01:20:23 p.m. EST, Elijah Stone
<elro...@elronnd.net> wrote:
What if its scope were delineated explicitly?
-E
On Wed, 9 Feb 2022, 'Pascal Jasmin' via Programming wrote:
> Just to follow up that this limitation/feature of f. is a necessary one.
> When using $: as recursion (potential multiple repeats) limiting its scope to
> just its (named) self is or at least feels like a prudent way to avoid
> recursion errors. Errors that are more painful than most since infinite
> recursion requires a "break" to get control back.
>
>
>
>
>
>
> On Wednesday, February 9, 2022, 11:29:25 a.m. EST, 'Pascal Jasmin' via
> Programming <programm...@jsoftware.com> wrote:
>
>
>
>
>
> dictionary page for f. mentions "problems" with f. when u includes $:
>
> this example seems ok though:
>
> + 1 : ' 0 & $: : (u/ % #) f.'
>
> 0&$: :(+/ % #)
>
> cut f.
>
> ' '&$: :([: -.&a: <;._2@,~)
>
> but:
>
> , 1 : ' u@cut f.'
>
> ,@(' '&$: :([: -.&a: <;._2@,~) (1 : 0))
>
> u y
>
> :
>
> x u y
>
> )
>
> adds some "explicit boilerplate"
>
> n&$: is an extremely useful pattern for providing default x argument to dyad.
>
>
> I still passionately hate the new AC train interpretation. (should be uACv
> instead of uACu), but it does offer an elegant-ish workaround.
>
> ([: -.&a: <;._2@,~) ((' '&) :)
>
> ' '&([: -.&a: <;._2@,~) :([: -.&a: <;._2@,~)
>
> that should be faster as well in that $: is an extra call that probably
> includes edge cases that interfere with f.
>
> An even more elegant workaround though is:
>
> mdef =: 2 : 'n&u : u' NB. monad default parameter n to dyad u
>
> cut =: ([: -.&a: <;._2@,~) mdef ' ' NB. same result as tacit AC modifier
> above.
>
>
> "explicit junk boilerplate" now removed.
>
> , 1 : ' u@cut f.'
>
> ,@(' '&([: -.&a: <;._2@,~) :([: -.&a: <;._2@,~))
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
