mathlib

a839f4dc - feat(number_theory/quadratic_reciprocity): change order of arguments … (#13311)

feat(number_theory/quadratic_reciprocity): change order of arguments … (#13311) …in legendre_sym This is the first step in a major overhaul of the contents of number_theory/quadratic_reciprocity. As a first step, the order of the arguments `a` and `p` to `legendre_sym` is swapped, based on a [poll](https://leanprover.zulipchat.com/#narrow/stream/116395-maths/topic/Quadratic.20Hilbert.20symbol.20over.20.E2.84.9A) on Zulip.