In my opinion, the language that comes closest to K's functionality and is also understandable by mere mortals is K itself. It is obviously extremely close to K

In my opinion, the language that comes closest to K's functionality and is also understandable by mere mortals is K itself. It is obviously extremely close to K's functionality and is a very simple language, the only reason it doesn't seem simple is that most people are used to verbose languages. A couple of days of practice is enough to make K readable, in my experience. Also, I am constantly amazed at how concise K is, easily rivaling not only conventional languages but also much larger array languages like APL or J. Arthur Whitney's taste in selecting primitives is out of this world.