Definition The set of all functions from X to Y: Yx={f|f:X→Y} Yx={f∈P(X×Y)|f:X→Y} X and Y are finite sets with x and y elements,respectively. IXI=z IYI=y,IYx=y Hengfeng Wei (hfweinju.edu.cn)1-10 Set Theory (III):Functions 2019年12月10日8/40Definition The set of all functions from X to Y : Y X = {f | f : X → Y } Y X = {f ∈ P(X × Y ) | f : X → Y } X and Y are finite sets with x and y elements, respectively. |X| = x |Y | = y, |Y X| = y x Hengfeng Wei (hfwei@nju.edu.cn) 1-10 Set Theory (III): Functions 2019 年 12 月 10 日 8 / 40