What might confuse you, is why Clojure even have true? and false? functions?
Its because conditional constructs like if, cond, when, test for truthy (aka
logical true) and falsey (aka logical false), not true and false. Nil and False
are falsey, and everything else is truthy.
Most of the time this is great, you can do:
(if (:a {}) ... ...)
Since if tests for truthy, keyword access of map values can be used as a valid
if condition.
But sometimes that's not what you want, sometimes you want nil to not be
considered false, or :error to not be considered true. In those cases, you wrap
the test condition in true? and false?. That way you're explicitly checking for
true or false, not truthy and falsey.
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