a = 0 a+a=0 a*a=0 絶対値ゼロ
b = '' b+b='' 空文字
c = [ ] 空配列
d = null 空集合
e = undefined 未定義
f = Object 全集合

他にも有るでしょうか？例えば、二次元配列
z[0] = [0,1,2,3,4,5,6,7]
z[1] = [0,1,2,3,4,5,6,7]
z[2] = [0,1,2,3,4,5,6,7]
z[3] = [0,1,2,3,4,5,6,7]
z[4] = [0,1,2,3,4,5,6,7]
z[5] = [0,1,2,3,4,5,6,7]
z[6] = [0,1,2,3,4,5,6,7]
z[7] = [0,1,2,3,4,5,6,7]

で、8*8のマスにはなりますが。
相互関係って何でどのように構築すれば良いのか悩んでいます。
ヒントを教えてください。