Global Instance CPermutation_in A a :
Proper (@CPermutation A ==> Basics.impl) (In a).
Global Instance CPermutation_in' A :
Proper (Logic.eq ==> @CPermutation A ==> iff) (@In A) | 10.

Lemma CPermutation_image A B : forall (f : A -> B) a l l',
CPermutation (a :: l) (map f l') -> exists a', a = f a'.