You know, 7 lines or not, name your goddamned variables. I'd fire someone who presented me with code like this.
I worked at a K shop last summer, and when I was learning the language, I tried using sensible variable names. I was told in no uncertain terms that, when you write K, local variables should be one letter, globals should be two, and functions should be three. It sounds like a total disaster, but after about two weeks (which is a long-ass time to learn a language), everything made perfect sense, and I really enjoyed u…
I haven't spent enough time with K to get to that point of naturalness. I do think a k like language that used slightly more natural nemonics could have much broader appeal with minimal impact on code length. IMHO what makes k (and j for that matter) concise is the primitives, how they combine naturally, and how iteration is subsumed to avoid any form "item at a time" code. That last bit is what separates it from the common map/fold idioms in other languages.