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In mathematics, a binary function, or function of two variables, is a function which takes two inputs. Precisely stated, a function is binary if there exists sets such that : where is the Cartesian product of and ==Alternative definitions== Set-theoretically, one may represent a binary function as a subset of the Cartesian product ''X'' × ''Y'' × ''Z'', where (''x'',''y'',''z'') belongs to the subset if and only if ''f''(''x'',''y'') = ''z''. Conversely, a subset ''R'' defines a binary function if and only if for any ''x'' in ''X'' and ''y'' in ''Y'', there exists a unique ''z'' in ''Z'' such that (''x'',''y'',''z'') belongs to ''R''. We then define ''f''(''x'',''y'') to be this ''z''. Alternatively, a binary function may be interpreted as simply a function from ''X'' × ''Y'' to ''Z''. Even when thought of this way, however, one generally writes ''f'' (''x'',''y'') instead of ''f''((''x'',''y'')). (That is, the same pair of parentheses is used to indicate both function application and the formation of an ordered pair.) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「binary function」の詳細全文を読む スポンサード リンク
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