Набрёл на коаны о функциональном программировании. Забавно.
Leroy instructs a student
The venerable master Leroy was walking with his student. Wishing to start a discussion with his master, the apprentice said "Master, I've heard that all loops must be replaced with tail-recursive functions. Is that true?" Leroy looked commiseratively at his student and replied "Foolish pupil, many tail-recursive functions are merely inefficient loops."
The student spent the next few weeks replacing tail-recursive functions with explicit loops. He finally showed his code to master Leroy, seeking his approval. Leroy hit him with a stick. "When will you learn? Explicit loops are a poor man's tail-recursive functions." At that moment, the student became enlightened.