Problems with “keep”

[cookieclickerer33]

I’m trying to make the opposite of the “keep” block but I can not get it to work

Outside of a custom block it works fine
But the second I make it into a custom block it doesn’t

I’ve tried a few things but I’ve concluded that I would need to know how the block works (what system is uses to get its results) to be able to fix it further

[cookieclickerer33]

I created my own definition for the block but I’d prefer to use the “keep” block as that one is just simply more stable

[pajamaclaws21]

Here is a solution:

[cookieclickerer33]

I always forgot about the change to the join block -_-
Why wouldnt run with inputs work tho

[pajamaclaws21]

This one allows for usage of (value, index, array).

[dardoro]

What's wrong with the most obvious

.

Hint:

[qw23]

For a more general approach
I made a function that groups all items by result of a function applied to each item.
E.g. it can divide a list of numbers into a list of primes and one of non-primes:

... or multiple sublist, grouped by a number's smallest divisor:

This is the implementation code
It will determine the result of the function only once for each item, and no (relatively inefficient) CONTAINS operation is required.

Update
I found a library block doing the same thing as my GROUP BY function (but slightly better); unsurprisingly it's called ; it's in the Frequency Distribution Analysis library.

[cookieclickerer33]

Very cool!
Unrelated note: I personally prefer “recall as (i)” rather than “let be (i)”

[pajamaclaws21]

@cookieclickerer33

“recall as (i)” rather than “let be (i)”

I think the word "let" describes what the block does pretty well. Check out MDN's description of the functionality of "let" in JavaScript.