gistfile1.txt

user=> (doc when)
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clojure.core/when
([test & body])
Macro
  Evaluates test. If logical true, evaluates body in an implicit do.
nil
user=> (doc if)
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if
  (if test then else?)
Special Form
  Evaluates test. If not the singular values nil or false,
  evaluates and yields then, otherwise, evaluates and yields else. If
  else is not supplied it defaults to nil.

  Please see http://clojure.org/special_forms#if
nil