APL/J/K code is really like mathematics, something that most programmers aren’t exposed to in the slightest. If you don’t grok it immediately, then you can actually just sit down and equationally work out the author’s exact thinking, in precise terms—and you level up as a side effect, so you don’t need to work out the same patterns every time you see them. That’s nigh impossible in C++!
Take it from someone who has seen both sides: the concision is a good, good thing.
