> (square: (x: y: square x + square y) 3 7) (x: x*x)58
This can be written up in many other forms, plus the possibility of currying deserves to be pointed out:
$ nix repl
nix-repl> (sq: (x: y: sq y + sq x) 2 7) (x: x*x)
53
nix-repl> (sq: (x: y: sq y + sq x)) (x: x*x)
«lambda @ (string):1:11»
nix-repl> (sq: (x: y: sq y + sq x)) (x: x*x) 2
«lambda @ (string):1:14»
nix-repl> (sq: (x: y: sq y + sq x)) (x: x*x) 2 7
53
nix-repl> (sq: x: y: sq y + sq x) (x: x*x) 2 7
53