A.C(m,n)=f(A(m,n),B(n,m))B.C(m,n)=f(A(n,m),B(n,m))C.C(m,n)=f(A(m,n),B(m,n))D.C(m,n)=f(A(n,m),B(m,n))
A.C(m,n)=f(A(m,n),B)B.C(m,n)=f(A(m,1),B)C.C(m,n)=f(A(n,m),B)D.C(m,n)=f(A(n,1),B)
A.僅用于按條件求和B.既用于按條件求和又用于無(wú)條件計(jì)數(shù)C.既用于按條件求和又用于按條件計(jì)數(shù)D.僅用于按條件計(jì)數(shù)