if-let(clojure.core)

Macro

bindings => binding-form test

If test is true, evaluates then with binding-form bound to the value of test, if not, yields else

; clojure/core.clj:1087
(defmacro if-let
  ([bindings then]
   `(if-let ~bindings ~then nil))
  ([bindings then else & oldform]
   (assert-args if-let
     (and (vector? bindings) (nil? oldform)) "a vector for its binding"
     (= 2 (count bindings)) "exactly 2 forms in binding vector")
   (let [form (bindings 0) tst (bindings 1)]
     `(let [temp# ~tst]
        (if temp#
          (let [~form temp#]
            ~then)
          ~else)))))

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