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4 (* ||A|| A project by Andrea Asperti *)
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7 (* ||T|| The HELM team. *)
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15 include "algebra/magmas.ma".
17 nrecord abelian_magma_type: Type[1] ≝
18 { amt_magma:> magma_type;
19 symm: ∀x,y: amt_magma. op ? x y = op ? y x