That's right, Devon. In older code you rarely encounter it except in the
form:
X ∘.× Y
for the outer product,
c/f X +.× Y for the inner product (although variants are possible).
But it also has a substantially different use in Dyalog APL — for function
composition. Thus
f∘g
is broadly equivalent to (J): f @: g
…and I see from aplcart that variants on this idea have proliferated in
recent years.
It's almost as if jot (∘) is the symbol of choice whenever some new squidgy
functionality is required. C/f J: (!.)
Whereas in former times the vendor would simply have introduced a new
quad-function, which militates against APL's one-function-one-symbol syntax
design habit.
Plus it helps keep APL free from English reserved words and thus
international in character.
Hence, I imagine, Raul's puzzlement at trying to induce the meaning of jot (
∘) from examples.
On Mon, 29 Jun 2020 at 16:18, Devon McCormick <[email protected]> wrote:
> As I recall, jot is a place-holder signifying "nothing going on here", a
> sort of no-op.
>
> On Mon, Jun 29, 2020 at 8:43 AM Raul Miller <[email protected]> wrote:
>
> > Huh...
> >
> > I took a look at that, and now I am puzzled by the significance of jot
> > (as in: jot dot times represents an outer product).
> >
> > The jot character shows up all over the place, but I can't quite wrap
> > my mind around its syntax, or significance.
> >
> > Maybe it's sort of like J's dot as a word forming (or token forming)
> > character, except it appears on the left side of the token instead of
> > on the right side??
> >
> > --
> > Raul
> >
> > On Mon, Jun 29, 2020 at 7:13 AM Ian Clark <[email protected]> wrote:
> > >
> > > A sort of NuVoc for APL that executes user-modified code.
> > > It's a polished piece of work. I'm impressed.
> > >
> > > Below is a copy/paste from a formatted email I've received from British
> > APL
> > > Association.
> > >
> > > NB: "16:00 BST is 11:00 USA:Eastern Time"
> > >
> > > Ian Clark
> > >
> > > ––––––––––
> > >
> > > "aplcart.info turns 1"
> > > by Adám Brudzewsky
> > > A BAA Webinar
> > > www.aplcart.info
> > >
> > > 2 Jul '20 16:00 BST
> > > The British APL Association is inviting you to a scheduled Webinar.
> > >
> > > Join the Webinar https://zoom.us/j/858532665
> > > ----------------------------------------------------------------------
> > > For information about J forums see http://www.jsoftware.com/forums.htm
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
> >
>
>
> --
>
> Devon McCormick, CFA
>
> Quantitative Consultant
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
