Slimey

hey so for a physics project im going to make a thermophysics simulator. my backend is going to be apl. ill use a 2d array of temperatures to represent a grid of temperatures. i want to change the temperature of tiles adjacent to tiles with differing temperatures. the quad diamond comes to mind.
({⊂⍵}⌺3 3) 3 3⍴⍳9
this gives me a nested array of adjacent tiles. im wondering how i can make the border values default to something else than 0, because i want 0 to be a possible temperature in the array. having the border values be something other than 0 which is outside of the domain of temperatu…

ive got two bqn functions:
MedianOfSortedLists ← ({𝕩{2|≠𝕨 ? ⊑𝕩⊏𝕨 ; ÷⟜2+´𝕨⊏˜𝕩-1‿0}⌊2÷˜≠𝕩}∘∧∘∾)
FirstMissingPositiveInteger ← {⌊´1+/¬𝕩∊˜1+↕≠𝕩}
both as solutions to these leetcode challenges respectively:
https://leetcode.com/problems/median-of-two-sorted-arrays/
https://leetcode.com/problems/first-missing-positive/

im new to bqn, coming from apl and im wondering about some ways to refactor these expressions.

median-function:
first off, im not proud of the algorithm in and of itself. its quite imperative by nature and requires the ? if-like statement (which i love as bqns response t…

awesome! i can see why this alternative solution is not preferred, although it removes the duplication of the code. what irks me most with that solution is the repetition of the ones again, but so be it.

is this flipover combinator present in any of the other array languages, like J or BQN? does it have a combinatory logic equivalent? i dont know much combinatory logic, but i find it intriguing. do you think apl should maybe implement such a combinator, or would it not be useful as a primitive due to likely under-utilization?

today i looked up the vector product in aplcart and was surprised by the repeated code
((1∘⌽⍤⊣ׯ1⌽⊢)-¯1∘⌽⍤⊣×1⌽⊢)
looking at the train-tree in ride, the two sides of the minus-fork were identical, with the exception of the negation of the ones present in the rotate functions. i was wondering: is there really no good way to shorten this in apl? could newer languages like bqn do it? could we make a nice combinator to solve this issue? well, its not really an issue, but it would be neat to have something to make it even more concise. any thoughts?

i thought of the mathematical function analysis way of solving it, as well as thinking of a possibility of solving the problem by computing twice, but didnt want to do those. cool solutions, thanks!

about your last solution: what do the ⍺←⊢ in the dfns of p do? i havent played much around with combining tacit and dfn forms, as it might look like here.
i assume p works so that it takes a left function and left argument and maybe "binds" it to the function like ⍣ composes its left argument with its left function. p also takes a right function and argument, where the right function is the con…

hello, im messing around with recursion and attempting to do things without loops in apl. im currently tackling the power operator, trying to use it to give me the nth element of a sequence, provided the nth element is beneath a certain limit.
i have the mathematical sequence: {2, 10, 50, 250,...}
and i wish to get the last element of it before the elements go over 10000.
in this example, the value i would be looking for is 6250, as the next element after that is 31250, which is more than 10000.