Functions in Clojure can behave differently depending on the number of
arguments they receive (their "arity"). A function can be written:
(defn foo [x]
(str "foo" x))
But you can also write:
(defn foo
([] "empty foo")
([x] (str "foo" x))
This will do different things depending on the number of arguments:
(foo)
=> "empty foo"
(foo "bar")
=> "foobar"
- James
On 4 September 2016 at 21:54, Charlie <[email protected]> wrote:
> I'm going through the Do Things: A Clojure Crash Course, and the following
> example (in REPL) is presented:
>
> (defn recursive-printer
> ([]
> (recursive-printer 0))
> ([iteration]
> (println iteration)
> (if (> iteration 3)
> (println "Goodbye!")
> (recursive-printer (inc iteration)))))(recursive-printer); =>
> Iteration 0; => Iteration 1; => Iteration 2; => Iteration 3; => Iteration 4;
> => Goodbye!
>
>
> This works as expected, but I don't understand the syntax of the function
> definition. Specifically: (defn recursive-printer ([] (recursive-printer
> 0)). Isn't the parameter list supposed to be a vector [] not ([]...)? Also,
> I don't see how [iteration] is resolved on the next line.
>
> Thanx for any help!
>
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