nixos/lib/default.nix

final: prev:
let
  inherit (prev) isFunction mkMerge mkIf;
in
rec {
  # Ternary operator
  # Exaample:
  # tern false 1 2 => 2
  # tern true 1 2 => 1
  tern = pred: x: y: if pred then x else y;

  # Right-associate and chain following single-operand functions
  # Example:
  # right f g h 1 => f(g(h(1)))
  right = f: g: tern (isFunction g)
    (right (x: f (g (x))))
    (f (g));

  mkIfElse = predicate: yes: no: mkMerge [
    (mkIf predicate yes)
    (mkIf (!predicate) no)
  ];
}