[derefr]

I would say that map being variadic on the set-of-things-being-mapped, and + being variadic on the set-of-things-to-add, is more of a "semantic axiom of the language" than plain-old DSL-esque "magic." It's like backtracking in Prolog: an extra thing you can assume everything in the language supports, that lets you code differently.

Learning "about" the variadicity of what are, in other languages, binary infix operations, is certainly a thing to learn, but it's a different kind of thing to learn than learning about "zipped" or "map". It's more of a "changing the way you think" kind of thing than a "knowing what tool to use" kind of thing. Like learning about destructuring pattern-matching, or actor-modelled crash-only software.

[sametmax]

The fact that you have to use the sentence :

"I would say that map being variadic on the set-of-things-being-mapped, and + being variadic on the set-of-things-to-add, is more of a "semantic axiom of the language" than plain-old DSL-esque "magic."

When you debate about any LISP based language is usually my clue.