[lmm]

There's a contradiction I always see in these pieces: they talk a lot about the importance of using the right data structure. But these languages get their incredible conciseness by not giving you any choice about your data structures; their array type is hardcoded into the language, and if you want to use something else then your code balloons.

[beagle3]

K basically has 3 data shapes:

atom (int, float, char, date, symbol, ...)

list (one dimensional array of atoms, dicts, flips or lists)

dict (a map from one list to another)

There's also a flip, which exchanges the first two indexes applied to an item (so, e.g., it effectively transposes a list of lists) but it is just sugar (both syntactic and semantic).

You can trust Whitney that all of these are properly implemented, including appends.

It's not often that you actually need more. I've discovered this after using K for a while, and going back to python.

Back in my pre-K (ha!) C++ and Python day, I had an awful lot of classes everywhere. After using K for a while, my Python and C both have much much fewer (structs in C more often than python, as C is missing python's dict). And the code has gotten much shorter and more efficient. Arguably, more readable as well. And I've essentially dropped C++ for C, because the extra complexity is just not worth it.