The kata is inspired by a Stack Overflow question.
It is easy to prove that
f(f(f b)) = f b for all functions
f : bool -> bool. But can you do it in less than 92 characters?
More specifically, your task is to prove the following lemma:
Lemma lemma : forall (f : bool -> bool) (b : bool), f (f (f b)) = f b.
And the size of your solution (including all declarations) should be 91 characters or less.
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