mathlib4
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feat: reflections, inversion sequences in Coxeter groups
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- Add theorem
List.length_eraseIdx_add_onetoData/List/Basic.lean, which states that ifi < l.length, then the length ofl.eraseIdx i plus oneis equal to the length ofl. - Add new file
GroupTheory/Coxeter/Inversion.lean. Define reflections, left inversions, right inversions, and inversion sequences. Prove their basic properties.
I decided to split #11408 (now closed) into two pull requests. This is the second one. The first is #11465.
- [x] depends on: #11465