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Adám
Adám
9:08 AM
CMC: Return the array '**' (i.e. ** isn't a valid solution) without using the character *.
 
ngn
ngn
@Adám anything to do with codegolf.stackexchange.com/a/115864?
⍕⍨⍳2 ⍝ with ⎕io←1
using the same trick, this one was close
 
H.PWiz
H.PWiz
9:36 AM
That can be also matched by 10 9⍕⍪⍳10
 
ngn
ngn
@H.PWiz yeah, that looks better
 
Adám
Adám
@ngn No. Comes from some internal development work.
@ngn Oh well, that was quick.
 
ngn
ngn
@GalenIvanov there's a simpler way to get the "diagonal" here
you could do prm'x without transposing it and then take the i-th elements from the i-th row of permutations
@GalenIvanov just use a double each on the indexing verb: |/+/(prm'x)@''!#x
 
H.PWiz
H.PWiz
9:53 AM
Also xnor pointed out that the solution is nearly >./ .+ in J, if anyone wants to fix it for rectangles and post
 
ngn
ngn
@GalenIvanov in ,// the first / is "reduce" (as in ,/ which is known as "raze" in the k/q world) but the second / is "converge" (like apl's fixed-point operator ⍣≡)
 
Galen Ivanov
Galen Ivanov
@ngn This is really nice
 
Galen Ivanov
Galen Ivanov
10:07 AM
Thank you for your help!
 
ngn
ngn
@GalenIvanov my pleasure :)
"case" looks interesting but it looks like oK doesn't support it
 
Galen Ivanov
Galen Ivanov
@ngn I'll take a look at the kx site
One more question: How to use \ (decode) when we don't know the number of necessary (binary for example) digits?
 
ngn
ngn
@GalenIvanov in my implementation i made 2\ return as many digits as necessary. i don't know if there's a way to do that in other ks
 
Galen Ivanov
Galen Ivanov
@ngn ok. I was thinking about using log or something, but it's too long
 
ngn
ngn
@GalenIvanov which challenge is that for? sometimes solutions work even with leading 0s
 
Galen Ivanov
Galen Ivanov
10:18 AM
Not related to anything in particular
 
ngn
ngn
(64#2)\x should give a sufficient number of bits
 
Galen Ivanov
Galen Ivanov
@ngn yes, it should work. I need to go now, bye!
 
ngn
ngn
for decimal there's .:'$x
@GalenIvanov bye!
 
 
1 hour later…
Galen Ivanov
Galen Ivanov
11:44 AM
@H.PWiz One way to do it is [:>./ .+#@{.{.] (take as many rows form the input as the length ot the first row, the needed rows are padded with zeros)
 
ngn
ngn
12:27 PM
@GalenIvanov what does it do without the [:? (i'm a j noob)
ah, i firured it out: (f g h i)x ←→ (f (g h i))x ←→ x f ((g h i)x), so that's why it needs to be "capped" with [:
 
Adám
Adám
12:47 PM
@ngn Which is a horribly hacky thing, imho. Dyalog's 2-trains are much saner.
Sometimes I just long for the super simple APL without namespaces, user-defined operators, function assignments, dfns, control structures, etc.
All these sometimes give absurd situations.
 
ngn
ngn
@Adám i agree, passing x as the left argument isn't so common. using an explicit ] for it wouldn't be too expensive
 
Adám
Adám
@ngn [ (⊣)?
 
ngn
ngn
@Adám well, i was talking in the context of monadic trains, like Galen's solution above
 
Adám
Adám
@ngn Oh, right. It is just that J convention has x for ⍺ and y for ⍵
 
Galen Ivanov
Galen Ivanov
1:07 PM
@ngn Yes, right. It's just capping the 2 verbs into a fork and not a hook
 
Lynn
Lynn
dfns.dyalog.com is very useful, but am I supposed to copy definitions out of it wholesale to use them in my code, or are these in the stdlib and I just don't know how to import 'em?
(Or; am I supposed to download the workspace and then import them)
 
Adám
Adám
@Lynn names ⎕CY 'dfns' or just ⎕CY 'dfns' if you want them all.
 
H.PWiz
H.PWiz
The workspace comes with a normal install of Dyalog
 
Lynn
Lynn
oh, neat :)
 
Adám
Adám
@Lynn You may want to put them in a namespace. E.g. you could do (⍎'dfns'⎕NS⍬).⎕CY'dfns'
@Lynn At the cost of performance, but gaining neatness, you can define the function WS←{⍺←⎕NS ⍬ ⋄ ⍺⊣⍺.⎕CY ⍵} so you can do (WS'dfns').pco 13. (Note: pre-17.0 you'll have to make that a tradfn or use error trapping.)
 
Galen Ivanov
Galen Ivanov
1:29 PM
@Adám It's really horrible with the trains sometimes, when you need forks and not hooks and it's a long sequence - there can be a lot of [:
I wish there were modifiers saying that what follows is a sequence of single verbs (to eliminate @), a train of forks (to eliminate [:) or a train of hooks (to eliminate () )
Of course these make sense in golfing, I doubt they really matter in "serious" coding
 
dzaima
dzaima
@Adám so just tradfns for user functions?
 
Adám
Adám
@GalenIvanov In Dyalog, for a longer sequence of monadics, I'd just do {f g h i j k ⍵}, but I can't figure out how to do that in J. 3(3:'x+y')4 doesn't seem to work.
@dzaima Yeah.
 
Lynn
Lynn
3 (dyad : 'x+y') 4 I believe
(dyad is just 4)
 
dzaima
dzaima
but tradfns are horrible (in comparison to my style dfns, at least) :|
 
Adám
Adám
@dzaima Why? The only real issue I have with them is that the "closing character" is the same as the opening character (∇) so you can't nest them. Oh, and having to declare your locals instead of declaring your globals is tedious.
 
Galen Ivanov
Galen Ivanov
1:40 PM
@Lynn Yes, 3(4 :'x+y')4 also works
@Adám 3 : is for monad
 
dzaima
dzaima
@Adám those, and that they force multiline code, can't be inlined, implicitly print non-shy results
also the returning system of them is strange
 
Adám
Adám
@dzaima Ah, good points. Inlining could be allowed just by allowing ⋄ after the header. I agree that everything should be shy (except in the session) but it isn't really a feature of tradfns per se.
@dzaima What do you mean? That they can return a function?
 
dzaima
dzaima
@Adám oh i guess that too, but the whole idea of having a return variable feels weird to me
 
Adám
Adám
@dzaima It is pretty neat sometimes when you need to assemble the result. Or for modifying an argument. E.g. 
text←Quote text
text,←'"'
text,⍨←'"'
@dzaima How about this one-liner tradfn: 
(y y)←Duplicate y
@dzaima (,2)≡⍴: 
 (a b)←Pair(a b)
 
dzaima
dzaima
@Adám oh god what
 
Adám
Adám
1:50 PM
@dzaima {⍺ ⍵}: 
 (a b)←a Juxtapose b
 
dzaima
dzaima
@Adám that feels more like abuse than the intended use
@Adám what that should do isn't anywhere near intuitive to me
 
Adám
Adám
@dzaima It throws an error if given anything but a length-2 vector.
 
dzaima
dzaima
trains are about hiding inputs and expressing transformations. one-liner tradfns are about hiding the transformations and expressing the inputs & outputs :p
 
Lynn
Lynn
hmph. I'm trying to solve adventofcode.com/2018/day/17 in Dyalog, and I seem to have something working gist.github.com/lynn/1dd09720a2d2e08a1602595c644c8827
but it's too slow to handle the real input
is anything obviously slow about this, other than the fact that it is a ⌺(3 3)⍣≡ ? is there any hope I can speed this up?
 
Adám
Adám
@Lynn I don't have time to look at that in detail right now, but if you just need display, you know you can use ]display? Alternatively, just turn ]boxing on -style=max.
 
Lynn
Lynn
2:04 PM
(the TiO link was too long, but it works on there. it does this:)
That works from the REPL, but I get line(33,0) : error AC0008: error (VALUE ERROR) executing line "]boxing on" in a script
 
Adám
Adám
@Lynn Right, you need ⎕SE.UCMD'box on'
 
Lynn
Lynn
on TiO at least
 
ngn
ngn
@Adám not just tedious, it's dangerous because the default is dynamic scoping - a tradfn can create and modify the local variables of its caller
 
Adám
Adám
@ngn A dfn can modify the local variables of its definer.
 
ngn
ngn
@Adám not caller. that is fine
 
Lynn
Lynn
2:21 PM
Dyalog doesn't happen to have something like sparse arrays, does it?
 
dzaima
dzaima
@Lynn as cool as stencil is, it's pretty slow as dyalog is pretty slow with non-vecorized functions. i opted for doing that aoc in java
 
Lynn
Lynn
mmm, I suppose you're right
 
Adám
Adám
@Lynn Not yet. Coming (as in you can make them yourself) soon™. You can kind-of hack them now.
 
dzaima
dzaima
@Adám magic arrays, if I recall correctly?
 
Adám
Adám
@dzaima Yes.
 
Lynn
Lynn
2:24 PM
I wanted to be like "woo, arrays! cellular automata!" about this but this problem is just too darn big
 
dzaima
dzaima
@Lynn todays aoc is much more cellular automata, and i did indeed solve it in apl
 
Lynn
Lynn
oh wow you're right
ugh that looks so much easier
I don't want to do this one anymore ._.
 
dzaima
dzaima
@Adám "as in you can make them yourself" so i still have to do the hard work, dyalog will just give me the ability to make e.g. + vectorize on my items, right?
actually you could probably do the horizontal maths for D17 vectorizedly, but sadly the input is much more vertical than horizontal
 
Adám
Adám
@dzaima It isn't really very hard. Just look-up indices in the list of indices, and then use that to look-up in the list of values. I think you'll have to :Implements ⍶+⍹ or something with a trivial definition.
 
ngn
ngn
@Lynn +1 in square brackets is a symptom you might want to use ⎕io←0 :)
 
dzaima
dzaima
2:31 PM
@Adám that's assuming a lookup indices array fits for the purpose, which it doesn't if i plan on inserting & removing a couple billion of items in groups
still want nice simple hashmaps in apl
 
Adám
Adám
@dzaima Wait, you do have hashed arrays, if that helps?
 
dzaima
dzaima
@Adám hashed arrays are ordered afaik, so removing a random element from it should be O(n)
 
Cows quack
Cows quack
@Adám highlights another thing I hate about J, because 3: is a verb, you have to have a space after the 3 otherwise it errors out
 
Adám
Adám
@Cowsquack I agree that that's horrible. Shy didn't they just allow array operand to ~‽ I'm currently proposing 3⍨ etc. Same goes for inner product which always needs a space on its left: +/ .*
 
H.PWiz
H.PWiz
3:30 PM
@Lynn I did try to speed it up just by (blindly) turning all of those conditions into one vectorised expression, and then replacing u l r dl (etc) with whole arrays. This is faster. But either I made a mistake or some of your logic is wrong. I have this case: tio.run/##K85JLM5ILf7/…
Also, I just closed my session without thinking, so I don't have any code to show
 
Lynn
Lynn
ah, my code is wrong ^^
 
dzaima
dzaima
@H.PWiz by some reason that picture made me want to have a go at doing the aoc in apl :|
 
Lynn
Lynn
sl←(dl∊1 6)∧(l=3)
sr←(dr∊1 6)∧(r=3)

should be l, r ∊3 4 5 or something, so that "water that touched a border" also propagates horizontally
for what it's worth, I had
0 = space
1 = # wall
2 = | falling water
3 = ~ horizontal water
4 = ⍨ water blocked off to the left
5 = ⍨ water blocked off to the right
6 = ≈ water blocked off at both sides
 
H.PWiz
H.PWiz
To make a single expression I just did:
f←{⍵+⍺×⍵=0}
⍵ f....f(n2×cond2)f(n1×cond1)
 
Lynn
Lynn
that's a clever way to make it fast!
thanks for poking at it anyway
 
dzaima
dzaima
3:50 PM
argh why cant i just get a non-O(n^2) \ ಠ___ಠ
that not existing completely breaks my idea of what i wanted to do, and my apl is way way too slow for a thing that took 5s in raw java
though reduce is a very ¨y operation anyway, forgot about that ಠ_ಠ
 
dzaima
dzaima
4:22 PM
what's an APLy way to transform 0 0 2 1 1 1 0 1 1 0 to 0 0 2 2 2 2 0 1 1 0 - aka replace /21+/ with all 2s?
 
H.PWiz
H.PWiz
Will there be 2 0s in the input?
 
dzaima
dzaima
@H.PWiz yeah, though that special-case is easily special-caseable
 
ngn
ngn
@dzaima (××2⌈/0,⊢)⍣≡
 
dzaima
dzaima
oh, meant /21*/, but doesn't really matter
@ngn that's O(n^2) though
 
ngn
ngn
@dzaima oh, is it for fastest-code?
 
dzaima
dzaima
4:28 PM
@ngn no, just fast code. For D17 AoC
 
ngn
ngn
@dzaima what do the 0s, 1s, and 2s represent? just curious
 
dzaima
dzaima
@ngn 0 = air, 1 = floor, 2 = settled flowing water
my idea was that i could at least have vectorizable instructions horizontally, but that needs that to be fast
 
ngn
ngn
4:44 PM
@dzaima shouldn't you replace in both directions? /1+21+/
 
dzaima
dzaima
@ngn that's easily done by executing the same thing on ⌽, but yeah
 
ngn
ngn
@dzaima maybe something like this? {a+a×b∊(⍵=2)/b←+\~a←×⍵}
 
dzaima
dzaima
@ngn oh wow that's beautiful
how do you even think of doing that :p
well i shouldn't really be asking, it is ngn who wrote it
 
ngn
ngn
@dzaima there's no magic, i'm just trying to use mostly vector operations
 
dzaima
dzaima
4:59 PM
@ngn yeah it's not magic, it's just a very obscure way of achieving that
 
ngn
ngn
@dzaima that ∊ bothers me though
 
dzaima
dzaima
@ngn yeah, that was my first thought too
 
ngn
ngn
5:18 PM
@dzaima i tried using only array operations but it's not faster :( {c←(1+⊃⌽b←+\0,2</a←×⍵)⍴1 ⋄ c[(⍵=2)/b]←2 ⋄ a×c[b]}
(⎕io←0)
 
dzaima
dzaima
@ngn wouldn't that be better written with @?
(not that i expect that to have a performance impact)
 
ngn
ngn
@dzaima maybe. i don't have @, my version of dyalog is old
 
dzaima
dzaima
ah
@ngn it's ~30% faster for me
 
ngn
ngn
@dzaima @ compared to no @?
 
H.PWiz
H.PWiz
@ is usually slower. I don't think it can ever be faster
 
dzaima
dzaima
5:25 PM
@ngn your new vs old
 
ngn
ngn
@dzaima ah
 
dzaima
dzaima
@H.PWiz it can tell that it doesn't need to copy the data of c
 
H.PWiz
H.PWiz
So, approx the same speed?
 
ngn
ngn
@dzaima c[ ]←2 should know that too
 
dzaima
dzaima
oh right forgot what the code does :|
hmm is there a way i could make dyalog do ⎕wa after every REPL entry? dyalog not collecting its garbage has frozen my system way too many times
(or alternatively a way to make linux not suck when it's low on memory)
 
H.PWiz
H.PWiz
5:33 PM
With a smaller MAXWS, would you still have a problem?
 
dzaima
dzaima
@H.PWiz then i wouldn't have as much ram available for dyalog when i need it :|
@ and [] seem to be around the same speed
@dzaima really just having the repl give me an option to do some post-processing would be nice. e.g. when i do, i almost never intend to print a 100000000-item array
 
dzaima
dzaima
5:53 PM
@Adám should this be happening?
 
Adám
Adám
@dzaima I've noticed it being broken. I need to investigate.
@dzaima I don't think there is an event for returning to the 6-space prompt, but there is one for printing, so if your expression only prints at the very end, you can attach a ⎕WA handler to that.
 
dzaima
dzaima
@Adám i wouldn't mind it ⎕WAing after each line printed really, where could i find that?
 
Adám
Adám
 
dzaima
dzaima
oh cool now 2 executed in the repl errors
 
Adám
Adám
@dzaima ⍨
 
dzaima
dzaima
6:04 PM
oh cool now everything is 2 :D
 
Adám
Adám
@dzaima Btw, this is what ]box etc. uses.
 
dzaima
dzaima
@Adám oh so doing that is gonna break it?
 
Adám
Adám
@dzaima Yeah. You could build in a hook in ⎕SE.Dyalog.Out.Filter which is the callback function.
 
dzaima
dzaima
how could i put stuff to execute on ws loading again?
 
H.PWiz
H.PWiz
⎕lx
 
Adám
Adám
6:10 PM
@dzaima ^ is per-workspace. WorkspaceLoaded Event is "global".
 
dzaima
dzaima
@Adám "global" to what/where is it stored?
also how do i do ]box on on startup
 
Adám
Adám
@dzaima It is a session event, so part of ⎕SE, and ⎕SE survives )load and )clear.
 
dzaima
dzaima
@Adám and dyalog closing & opening?
 
Adám
Adám
@dzaima Save your session with boxing on or make it part of setup.dyalog.
 
dzaima
dzaima
what is save session
 
Adám
Adám
6:14 PM
@dzaima the FileWrite method (which has a menu entry on Windows).
 
dzaima
dzaima
@Adám i'm not on windows, so what's a FileWrite
 
Adám
Adám
@dzaima 2⎕NQ'⎕SE' 'FileWrite'
 
dzaima
dzaima
and what do i do with that. sorry for asking literally all the questions :|
so the workspace, REPL history & session are all stored separately? ._.
 
Adám
Adám
@dzaima '⎕SE'⎕WG'File' is where your current ⎕SE came from. You can ⎕WS this property to choose another filename, then 2⎕NQ'⎕SE' 'FileRead' to load that file or 2⎕NQ'⎕SE' 'FileWrite' to save your current session to the selected filename. On startup, APL loads your default session or whichever session you specify from the commandline or with a environment variable. You can use this to prepopulate ⎕SE.
If you don't change the name, just save to the current file, you'll get your ⎕SE changes back next time you start.
 
dzaima
dzaima
 
Adám
Adám
6:23 PM
@dzaima Somehow you accessed part of our overnight build process. That shouldn't be possible. How did you get there?
 
dzaima
dzaima
..executed 2⎕NQ'⎕SE' 'FileRead'
so what i should do is ]box on, then 2⎕NQ'⎕SE' 'FileRead' and now restarting dyalog should start with boxing on? cause that's not happening
 
Adám
Adám
@dzaima No, ]box on then FileWrite!
 
dzaima
dzaima
@Adám right, miscopied that message. that doesn't work
 
Adám
Adám
@dzaima Well, now you session file is probably well messed up. You may want to reinstall, or copy that file from the installation image. Next time, make a copy to somewhere else before you begin experimenting.
 
dzaima
dzaima
6:41 PM
no the session file is equal to the starting one
 
Adám
Adám
@dzaima Just starting APL, ]box on then saving the session should do the trick. If that doesn't work, then email support@ or ping me during office hours and we'll sort it out.
 
dzaima
dzaima
@Adám saving the session ≡ running 2⎕NQ'⎕SE' 'FileWrite', which should write to '⎕SE'⎕WG'File', right?
 
Adám
Adám
@dzaima Yes.
 
 
2 hours later…
dzaima
dzaima
9:11 PM
oh monadic ⍮ is doing strange things
 
Adám
Adám
@dzaima It looks like it is doubly enclosing. Should be ,⊂.
 
dzaima
dzaima
and it violates ⎕boxsimple←0 :|
 
Adám
Adám
Hm, another idea for an additional operator: {⍺←⊢ ⋄ 0 1000::⍺ ⍵⍵ ⍵ ⋄ ⍺ ⍺⍺ ⍵}
 
dzaima
dzaima
@Adám personally i hate allowing things to rely on errors
e.g. if there's a thing that relies on ⍸ erroring on non-0/1 values, it'll break if the domain of it is extended
 
Adám
Adám
@dzaima Yes, me to, and more so over time. I'd much rather write a lot of code to pre-check. But I was trying to solve this which would be ⍎⌺←'⍞'⊣⎕RTL∘← assuming ⌺ for the above and ← is Sink.
@dzaima True. E.g. I don't think we can ever extend monadic ~ due to people using it as Boolean checker. Similarly, we can't introduce operator phrases, because people use ∘∘∘ to intentionally throw an error (they should use ⎕SIGNAL).
 

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