I find some unfamiliar syntax in Example "In[215]…". What is the solid dot following "10^" and in the first argument of StringJoin? I thought I knew functional notation...

Thank you,

Vince

Vince,

That's a position-coded curry syntax that I invented and use extensively. It's found in Appendix A of my book but here it is.

[Bullet] /: f[pre, [Bullet] , post_] := With[{n = Length[List@pre], m = Length[List@post]} , Curry[f, Join[Range[n], {n + m + 1}, Range[m] + n]][pre, post] ];

Put the solid dot, aka bullet (Option-8 on most keyboards), in the position of a function's argument list to curry that parameter. As per operator forms in general, It streamlines syntax in data pipes.

Thanks to Jose Martin-Garcia from WRI for help in refactoring from an earlier version.

That's right, so that the bullet can be placed anywhere for any function taking arbitrary number of parameters.

Since I'm on Windows and don't have a shortcut for 'bullet', I find \[NumberSign] a bit faster: esc # esc

Use whatever you like - ideally this would be standardized in the language.

But I would advise against [NumberSign] in particular: (1) it looks too similar to Slot notation - especially if you share code, you can't control other users' fonts. (2) how is 3 keystrokes in esc # esc faster than 2 keystrokes in option 8 (alt 8 on Windows)?

Thanks! But I think you missed one _ character after the f, which makes a big difference:

ClearAll[\[Bullet]];
\[Bullet] /: f_[pre___, \[Bullet], post___] := With[
   {
    n = Length[List@pre],
    m = Length[List@post]
    },
   Curry[f, Join[Range[n], {n + m + 1}, Range[m] + n]][pre, post]
   ];

I have to say, this is perhaps the coolest thing I've stumbled across in a long time. As another Windows user, I couldn't find an easy key combo to enter the bullet point, so instead I found that hitting Escape bu Escape to print out \[Bullet] in a notebook works pretty well (and should be OS-independent). It's perhaps not as fast as Option + 8, but it should be good enough.

As somebody who really likes to use RightComposition, this would be a fantastic feature to build into the language, as it's quite a pain to have to use parentheses (and the &) when chaining many "pure functions" together. Until then (assuming it would be implemented) I think I'll be including this definition into more of my projects.

Hi Alan, I liked the functional dataflow stream! Would be great if you could share this stuff on the "functions" page somewhere. The now famous [Bullet] solution baffles me a bit so might deserve a new thread. I tried to work with it (following the above definition) but it seems to work only on self defined functions and not on build in. Anyway again look forward to follow a new stream.

Windows Alt-7 on numeric keypad indeed produces a bullet.

Thank you!