correct. ⍨ is the commute operator when used dyadically. I generally use it
to preserve right to left reading vs nested parentheses or variable
assignment.
)help ⍨
- Rowan
On Sun, Apr 12, 2020, 5:18 AM Otto Diesenbacher-Reinmüller <
ok...@diesenbacher.net> wrote:
>
> Hi Rowan,
>
> ⍨ operator: you are using it to avoid parentheses?
>
> Beside of restructuring code, avoiding duplicate code-fragment and
> parentheses, ⍨ has no "functional" impact?
>
> br & many thanks - Otto
>
> Rowan Cannaday <cannad...@gmail.com> writes:
>
> > addendum, forget an extra ⍳≢
> >
> > {(⍵⍴⍨≢⍵)⊂⍨(≢⍵)↑⍺/⍳≢⍵}
> >
> > Cheers.
> >
> > On Sat, Apr 11, 2020 at 9:19 PM Rowan Cannaday <cannad...@gmail.com>
> wrote:
> >
> >> quick attempt:
> >>
> >> 3 {(⍵⍴⍨≢⍵)⊂⍨(≢⍵)↑⍺/⍵} 1 2 3 4 5 6 7
> >> ┏→━━━━━━━━━━━━━━━━━━┓
> >> ┃┏→━━━━┓ ┏→━━━━┓ ┏→┓┃
> >> ┃┃1 2 3┃ ┃4 5 6┃ ┃7┃┃
> >> ┃┗━━━━━┛ ┗━━━━━┛ ┗━┛┃
> >> ┗∊━━━━━━━━━━━━━━━━━━┛
> >>
> >>
> >> On Sat, Apr 11, 2020 at 9:02 PM Otto Diesenbacher-Reinmüller <
> >> ok...@diesenbacher.net> wrote:
> >>
> >>> Hi APLers!
> >>>
> >>> as I had a look into the archives, it seems ok, to post non bugs and
> >>> other topics not closely related to gnu-apl, but APL in general (for
> >>> sure, utilizing gnu-apl)? If my following post is offtopic please
> >>> excuse, and please let me know, where would be right place to discuss.
> >>>
> >>> So - i am quite new to APL, my road to APL? Some weeks ago, being a
> >>> hobbyist/partly professional Common Lisper, I stumpled upon April
> >>> (https://github.com/phantomics/april) and was fascinated by
> >>> APL. Always hungry for /something/ to get rid of Excel, I am starting
> >>> to explore the world of arrays ;).
> >>>
> >>> Having browsed through "Mastering Dyalog APL"(Legrand) and "APL_ The
> >>> Language and Its Usage"(Polivka/Pakin), to get some experience, I am
> >>> trying to solve (the easy parts) of the APL Dyalog Problem Solving
> >>> Competition (https://www.dyalog.com/student-competition.htm).
> >>>
> >>> I would like to share my experience, discuss the obstacles I
> >>> encounter, and especially get some advice/hints from you, the
> >>> experienced APLers! Perhaps this will lead to some blog-posts...
> >>>
> >>> Let's start with the first one:
> >>>
> >>> 1 chunk monkey
> >>> (
> >>>
> https://www.dyalog.com/uploads/files/student_competition/2019_problems_phase1.pdf
> >>> )
> >>>
> >>> "Write a function that, given a scalar or vector as the right argument
> >>> and a positive (>0)integer chunk size n as the left argument, breaks
> >>> the array's items up into chunks of sizen. If the number of elements
> >>> in the array is not evenly divisible by n, then the last chunkwill
> >>> have fewer than n elements. Hint: The partitioned enclose function ⊂
> >>> could be helpful for this problem."(from the exercise)
> >>>
> >>> hmmm, as in the exercise stated, dyadic ⊂ (partition) is to be used.
> >>> So the real challenge is to generate the correct vector as left
> >>> argument for ⊂, right?
> >>>
> >>>
> >>> ⍝ first try:
> >>> ∇ z← size chunkmonkey1 a
> >>> z←((⍴a)↑(size/⍳⍴a)) ⊂ a
> >>> ∇
> >>> ⍝ BUT
> >>> ⍝ - doesn't work with a scalar as asked
> >>> ⍝ - ((⍴a)↑(size/⍳⍴a)) seems inefficient, as we make a to big
> >>> ⍝ vector and cut it down afterwards... Is this a common/fine
> >>> ⍝ pattern?
> >>>
> >>>
> >>> ⍝ second try:
> >>> ∇ z← size chunkmonkey2 a
> >>> →((0=≢⍴a)∧1=≢a)/skalar ⍝ matches a skalar, but not ''
> >>> z←((≢a)↑(size/⍳≢a))⊂a ⍝ ≢ or ⍴ in this case?
> >>> →0
> >>> skalar:
> >>> z←a
> >>> ∇
> >>>
> >>> ⍝ correct, but feels clumsy...
> >>> ⍝ - ≢ seems more acurately than ⍴ in this case?
> >>> ⍝ - should be doable without jump?
> >>> ⍝ - still the inefficient vector
> >>>
> >>> Final thoughts for now:
> >>>
> >>> What I learned/understood with this exercise: / is not only reduce
> >>> (operator), but also dyadic functions filter and especially expand
> >>> (not all APL-variants?).
> >>>
> >>> Checking for types is not easy. 0=⍴N is a scalar. Howto check for a
> >>> string?
> >>>
> >>> br & and many thanks for any hints, Otto
> >>>
> >>> --
> >>> Dipl. Ing. (FH) Otto Diesenbacher-Reinmüller
> >>> diesenbacher.net
> >>> Salzburg, Österreich
> >>>
> >>>
>
>
> --
> Dipl. Ing. (FH) Otto Diesenbacher-Reinmüller
> diesenbacher.net
> Salzburg, Österreich
>
