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Hiredman is working on a nice implementation of tuples in Clojure. But, just for fun, I wanted to whip up the absolute minimum viable O(1) tuple possible.

The result is this macro:

(defmacro tuple
  [& xs]
  `(fn [idx#] (case idx# ~@(mapcat list (range (count xs)) xs))))

Try that in Ruby or C# ;)

So, (tuple "foo" 5 :bar) returns a function that takes an index and returns the value at that index in the arguments to tuple, i.e. ((tuple "foo" 5 :bar) 1) returns 5.

The macro compiles to a case form which dispatches in constant time, although it’s not as fast as Hiredman’s implementation, or even Clojure’s native vector.