The APL Orchard

8:13 AM

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What valence does this APL train have? code-golf sequence decision-problem apl Context In APL, trains are tacit sequences of monadic/dyadic functions that can be called with one or two arguments. We'll code something to check if a given train follows the correct structure we need in order to have...

I'm about to post this APL-related challenge to the main site. If anyone has any last comments to make, now is the time :)

Adám

8:27 AM

@RGS Maybe cross-post in TNB?

RGS

Yeah

Adám

@RGS You could consider a recursive definition (too).

RGS

@Adám That is true and tbh it was how I understood the structure of trains in the first place... But I think providing one correct algorithm suffices. Would you agree?

Adám

Sure, it was just an idea.

RGS

Thanks :)

Btw if anyone here speaks Portuguese and is really really interested, I can get you a "seat" in the 2nd part of my "Learn APL with neural nets" workshop... Except if you are reading this you probably know "too much" APL for the rhythm of the workshop.

Adám

8:42 AM

Haven't seen J.Sallé for a while…

@RGS I'm writing a solution, so hold for a while if you want me to check your examples.

RGS

@Adám Alright, I can wait for a bit ofc.

Adám

@RGS Maybe add a couple of longer valid trains?

RGS

@Adám in particular, valid monadic trains, no? I am having a hard time coming up with interesting long dyadic trains

Adám

@RGS MDBBBBDB is an interesting long dyadic train.

RGS

Here's the 5 new example trains,
in the second line of `t`:
https://tio.run/##lVLNagMhEL77FCI9aFmWlhwKhRIQrz5BSYPdNVlLVhfXBgJ9963OGBoSCq2Hmc9x5hvnZzqlIfjVsrhxCjHRaHwfRnK@WULQ0s7W9vxpJQjp7Y520Zpktyka57l4JjSfg/X7NNCXytEW5Xziq4Y@PghwiTZ9Rk8Zaz9CDqyO3RBcZznTSjJBdyHSLXW@0OwtR1ZR87p5OwZvetdxyF1TV973EA482nY0qRt4ZG9cf0kBYs25OmNxf8caivE/vP3pf7RrJESpbmmTndOcu/G6IakopvMrU0XIIjTcNWI0g0WCRYJFAVaI0V9XjUpWVYMudAZQQwmR2Q2ptJTywktJpTBThhIMSF7xhpRpQEllIgnbApW1Zpqs7zk2rKH8ZjTNTVdF6cvVfPNqVFbI8nK1WvB0NHkLOpsf/5Tl909WovM3UrZAXcUXfzHFsrJJXFyOYlm@AQ

Adám

9:20 AM

@RGS Can you reorder the examples so the results are lexicographical?

RGS

As in a dictionary, or with same lengths grouped? (I'm assuming you are talking about the trains)

Adám

@RGS No, the results. First all the 0 0s, then all the 0 1s then all the 1 0s then all the 1 1. Secondary sorting doesn't really matter.

RGS

@Adám Done

Adám

9:39 AM

@RGS OK, I have a reference solution (not very APLy) that matches your results.

RGS

Alright, it is time to post it, then

Feeds

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Q: What valence does this APL train have?

Context In APL, trains are tacit sequences of monadic/dyadic functions that can be called with one or two arguments. We'll code something to check if a given train follows the correct structure we need in order to have a sound train. Task Given the sequence of function arities in the train, deter...

Elias Mårtenson

11:08 AM

OK, I have implemented hashmaps in a somewhat silly, but straightforward way. I'd like someone to critique the design.

Basically, you create a map using the following m ← map 3 2 ⍴ "key" "value" "key2" 1 :key3 (1 2 3)

In other words, the argument is a two-column array with key/value pairs.

Since KAP values are immutable, updating a value returns a new map: m ← m mapPut :key4 "new value"

Getting a value is done like this: m mapGet :key4

ngn

"I'd like someone to critique the design" - you've come to the right place :D

Elias Mårtenson

Finally, if the right argument to mapGet is an array, the call returns an array of the same dimension with the respective values in each cell: m mapGet 2 2 ⍴ "key" :key3 :key3 :key3

@ngn Yeah, that's what I was hoping.

There is a mapRemove as well that does what you'd expect.

Oh, and the map is ordered. That way you can convert the entire thing into an array if you want.

Finally, the names beginning with a colon, like :foo are keywords. They are basically symbols in the exact same way as they work in Lisp.

Arrays can also be used as keys in the hashmap. Equivalence is the same as ≡

ngn

11:24 AM

immutability - great!

2-column - why not a pair of nested arrays: (keys values)? this way the keys and values can separately benefit from more compact representation.

if keys and values are separate vectors, you could also reuse your dyadic iota impl to search in the keys

"hash"maps - is there any actual hashing involved in this (or planned to be)?

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