6.1 Operations on the set o Definition 1: An unary operation on a nonempty set S is an everywhere function ffrom S into S; A binary operation on a nonempty set S is an everywhere function f from sXSinto S; A n-ary operation on a nonempty set s is an everywhere function f from Sn into S closed6.1 Operations on the set ⚫ Definition 1：An unary operation on a nonempty set S is an everywhere function f from S into S; A binary operation on a nonempty set S is an everywhere function f from S×S into S; A n-ary operation on a nonempty set S is an everywhere function f from S n into S.  closed