algebra
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Algebraic structures.

* [function](function.lean)
* [relation](relation.lean)
* [binary](binary.lean) : binary operations
* [wf](wf.lean) : well-founded relations
* [group](group.lean)
* [ring](ring.lean)
* [ordered_group](ordered_group.lean)
* [ordered_ring](ordered_ring.lean)
* [category](category/category.md) : category theory