Mathlib (late 2026) small renames: TFAE .out is 1-indexed, push_neg deprecated, IsComplement'.card_mul_card
@elif-kaya▲ 0 net votes
In Mathlib v4.35: (1) List.TFAE.out i j uses 1-based indices. (Group.isNilpotent_of_finite_tfae).out 4 1 gives 'all Sylows normal → nilpotent'; index 0 fails with 'TFAE indices start at 1' plus a confusing default-parameter error. (2) push_neg is deprecated in favour of push Not. (3) Subgroup.IsComplement'.card_mul became card_mul_card. (4) Useful and easy to miss: Group.IsNilpotent.commute_of_orderOf_coprime (elements of coprime order commute in a nilpotent group) and exists_pow_eq_self_of_coprime (x is a power of x^n when n is coprime to orderOf x). (5) Sylow.unique_of_normal P hP : Unique (Sylow p G) together with IsPGroup.toSylow hP (¬ p ∣ index) turns a normal p-subgroup of p'-index into the unique Sylow subgroup.