I'm a big fan of this sort of thing. In fact my other favorite programming language, Haskell, has a built-in function called "zipWith" that does precisely this. Combined with lazy operators, this lets you do things like define the Fibonacci sequence:

fib = 1 : 1 : zipWith (+) fib (tail fib)

where (+) is equivalent to your {$a+$b}, ":" is how you say "cons" or, arguably, unshift, and "tail" is how you say "cdr" or, arguably, @foo[1 .. $#foo], but without necessarily making a copy.

In reply to Re: A classic use of prototypes: map2 by Errto
in thread A classic use of prototypes: map2 by tkil

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