Commit 2022-02-05 05:19 b0d9761b

feat(ring_theory/hahn_series): add a map to power series and dickson's lemma (#11836) Add a ring equivalence between hahn_series and mv_power_series as discussed in https://leanprover.zulipchat.com/#narrow/stream/217875-Is-there.20code.20for.20X.3F/topic/induction.20on.20an.20index.20type/near/269463528. This required adding some partially well ordered lemmas that it seems go under the name Dickson's lemma. This may be independently useful, a constructive version of this has been used in other provers, especially in connection to Grobner basis and commutative algebra type material.