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Bubbler
Bubbler
01:22
Random idea: Add an option to Scan to indicate that the operand function is associative, so that it can run in O(n). Using non-associative functions with that option will result in scanl1 common to other languages.
Marshall
Marshall
@Bubbler BQN and dzaima/APL work this way normally, and don't have an O(n^2) scan operator.
Bubbler
Bubbler
@Marshall Oh. Didn't know that
dzaima
dzaima
@Marshall as now we have headers for ambivalent functions, how about making ⊘ be reduce on a specific axis?
(i don't know what particularly would that be, just throwing out the idea as i remembered about it)
Marshall
Marshall
@dzaima I would prefer a second reduce 1-modifier for a lot of reasons. You'll usually use the first axis, Reorder Axes is currently the only function that uses axis numbering at all, and Rank provides the flexibility of positive or negative ranks.
I took another look at @Adám's ˝ and it doesn't seem all that similar to ˜ in monospace fonts, so I think I will probably end up using that.
Also I think ⊘ is still pretty useful for making those almost-perfectly-ambivalent tacit functions work.
dzaima
dzaima
01:44
@Marshall may be my bias on having first-axis reduce longer in dzaima/APL, but i don't think i've had a much stronger need for one over another for matrices. (and what do i know, i'm not that good at high rank stuff anyways)
Marshall
Marshall
@dzaima I think I've always wanted the first-axis form so far. But if you're working with matrices, F˝˘ is just as short as F⊘1, and roughly as readable (not that good in either case).
 
3 hours later…
Moonchild
Moonchild
04:27
@Bubbler for builtins, easy enough to just check. Beyond that, I think scanl and scanr should be separate operators, not separate flags given to a single op
 
6 hours later…
RGS
RGS
10:40
When I'm looking to trap a single error code in a tradfn and then run some code if that error code is triggered, can the :Trap notation be shortened?
Adám
Adám
@RGS No, you still need five statements. However, you may be able to use a utility dfn inline.
RGS
RGS
@Adám you mean by using the :: dfn syntax?
Adám
Adám
@RGS Yes.
RGS
RGS
10:58
@Adám +← 1 Thanks for the suggestion
 
7 hours later…
Adám
Adám
17:48
CMC: Write the shortest possible statement that returns whether the statement is being run inside a dfn/dop or not.
Marshall
Marshall
APL\360 solution: 0
Adám
Adám
@Marshall Nice. Works in APL+Win too!
Adám
Adám
18:08
@Marshall btw, the cmc is unsolvable in bqn, isn't it?
Marshall
Marshall
@Adám Assuming you translate "dfn/dop" to "block", yes. Code just runs; it doesn't know how it's been defined.
I think an entire file should work identically to an immediate block even though there are no braces. So there isn't really any use for this "not in a block" concept.
Adám
Adám
@Marshall Right. Well, I would have wanted Dyalog APL to be the same language inside dfns too, but that doesn't mean I can't detect the current what's going on.
Marshall
Marshall
18:23
@Adám You can find whether a given bit of code is inside curly braces statically by looking at the source code though. Why would you need to do that in a running program?
Adám
Adám
@Marshall I didn't say I needed it.
RGS
RGS
18:59
@Adám I don't understand
Adám
Adám
@RGS I'm challenging the readers to write an expression E such that E returns a truthy/falsey value indicating if E was executed inside a dfn/dop or not.
RGS
RGS
@Adám if not iniside a dfn/dop, then it was ran inside a tradfn? or are there any other options?
TessellatingHeckler
TessellatingHeckler
right now I have a tacit function which seems to behave differently depending if it's bound to a name or not.
RGS
RGS
@TessellatingHeckler that sounds whacky
Adám
Adám
@RGS Outside a dfn/dop can be in a tradfn/tradop, in the session, or in a script.
@TessellatingHeckler Yeah, that can happen. Wait, a tacit function. Hm.
TessellatingHeckler
TessellatingHeckler
19:04
well
Adám
Adám
I knew it could happen to dfns.
TessellatingHeckler
TessellatingHeckler
more clearly, it's probably a line of APL code which contains one or more tacit functions 
      ∨/((1 ¯1⍴⍨≢)⍷⍨(×2-/⊢))10⊥⍣¯1⊢121314
1
      isWobbly←∨/((1 ¯1⍴⍨≢)⍷⍨(×2-/⊢))10⊥⍣¯1⊢
      isWobbly
 ∨/    1 ¯1  ⍴⍨ ≢  ⍷⍨  × 2  -/ ⊢    10  ⊥⍣ ¯1 ⊢
      isWobbly 121314
0
it's trying to check if the digits of a number alternate higher/lower/higher/lower (than the previous digit)
1 if they do, 0 if not
RGS
RGS
@Adám okok; and marshal's solution works in Dyalog APL?
Adám
Adám
@RGS No. E.g. it fails in {0}⍬
@TessellatingHeckler The 1 was from an expression, not a train. isWobbly is a train.
So in the initial expression, ∨/ is applied to the result of ((1 ¯1⍴⍨≢)⍷⍨(×2-/⊢))10⊥⍣¯1⊢
In the train, ∨/ is applied to the argument. 
       ∨/((1 ¯1⍴⍨≢)⍷⍨(×2-/⊢))10⊥⍣¯1⊢ 121314
1
      (∨/((1 ¯1⍴⍨≢)⍷⍨(×2-/⊢))10⊥⍣¯1⊢)121314
0
TessellatingHeckler
TessellatingHeckler
I see what you're saying; is there any reason I could understand why it changes to be a train by being bound to a name?
RGS
RGS
19:08
@TessellatingHeckler it just doesn't parse as a train, cf: 
      (∨/((1 ¯1⍴⍨≢)⍷⍨(×2-/⊢))10⊥⍣¯1⊢)121314
0
Adám
Adám
@TessellatingHeckler If the rightmost part is a function, you have a train. If the rightmost part is an array, you have an expression.
dzaima
dzaima
@TessellatingHeckler compare e.g. ---1 and f ← --- ⋄ f 1 - it's just a completely different situation
TessellatingHeckler
TessellatingHeckler
@Adám ah, it's not the binding to a name, it's the removing of 121314 changing it?
@dzaima good simple example; (-(-(-1))) first and ((-1)-(-1)) as a train second
Adám
Adám
@TessellatingHeckler Exactly.
TessellatingHeckler
TessellatingHeckler
Thanks :)
about the only thing I know is different in a dfn is something like dynamic scoping changes to lexical scoping
Adám
Adám
19:15
@TessellatingHeckler Nice. I guess one could use that. (Now I have to try.) Though there's a much simpler and shorter solution.
Hm, no, if the current function is defined by its caller, the two scoping rules would be behave identically.
TessellatingHeckler
TessellatingHeckler
@Adám Not sure how I could use that; but what about 0≤≢⍵: 1 ⋄ 0 ? since guards are only in dfns, if it works it's in a dfn, if it throws a Syntax Error, it isn't.
Adám
Adám
@TessellatingHeckler Nice, but then you have to trap the error and return 0.
@TessellatingHeckler 1⊣⍵⊢⎕trap←0,'E0' kind-of works, except it prints the 0 instead of returning it.
TessellatingHeckler
TessellatingHeckler
@Adám interesting; and I can tell that's not the right direction for the simpler and shorter solution you'll have in mind.
Adám
Adám
19:31
@TessellatingHeckler Right.
@TessellatingHeckler Unfortunately, there are actually quite a few differences.
OK, I have a 7 byte "cheaty" solution, and a 13-byte solution that actually relies on a real difference in the language.
 
2 hours later…
Paul Mansour
Paul Mansour
21:45
@Adám I must be missing something because I have a trivial and obvious 8 byte solution and I don't think it's cheaty at all.
Adám
Adám
@PaulMansour I did say "cheaty" in scare quotes, because there really isn't such a thing as cheating here if it works. Let's see yours!
Paul Mansour
Paul Mansour
2=⎕NC'⍵'
Adám
Adám
Mine is ×⎕NC'⍵'
Paul Mansour
Paul Mansour
Yours wont work in the session.
Adám
Adám
Oh, you're right. It doesn't work anywhere, actually. :-(
RGS
RGS
21:49
@Adám lol
Adám
Adám
Now I wonder how I made that mistake. Didn't I test it‽
@PaulMansour Now, can you come up with a solution that doesn't rely on asking such a "question" of the interpreter, but rather relies on an actual difference between the APL language used in dfns/dops and the APL language used outside them?
Paul Mansour
Paul Mansour
22:02
@Adám Not off the top of my head, but I'll be intrigued to see your solution, though arguably the existence of omega is indeed "a actual difference between the APL language used in dfns..."
Adám
Adám
@PaulMansour ⊢f a←⍎'f←≡⋄1' or the easier-to-understand, but not-really-one-expression f←≡⋄⊢f a←1
TessellatingHeckler
TessellatingHeckler
@Adám I switched tab to the Dyalog 17.1 interpreter and pressed F1 to look in the help for dfns, and ended up at help.dyalog.com/dmx/17.1 . I'm not sure how, since it doesn't do that after a restart, and I had not used ⎕DMX, but that's a page with no content and links to "Dyalog for Windows" which don't work, in case that's a useful report.
Adám
Adám
@TessellatingHeckler I know about that. It is part of an ambitious project I reckon we've given up on. The idea was that people could go online to get more specific info about the error they hit.
Paul Mansour
Paul Mansour
@Adám Wont really work in all circumstances though, will it?
TessellatingHeckler
TessellatingHeckler
@Adám OK
Adám
Adám
22:10
@PaulMansour What do you have in mind?
Paul Mansour
Paul Mansour
f←5 on the line above?
Moonchild
Moonchild
@Adám on unix, you could do like gcc does and use gnome-terminal/iterm2 escapes to make error messages links
Adám
Adám
@PaulMansour Fair enough.
@Moonchild That isn't the problem. The IDEs already makes URLs clickable. The problem is actually collecting all that information about every error type.

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