您大概理解有點偏差。Real Analysis裏麵隻是以線作為輔助理解工具，從未提及長度。數是沒有長度的。

來源: 於 2023-12-22 20:28:46 [舊帖] [給我悄悄話] 本文已被閱讀：次

Def: the set of real numbers R is an ordered field which has the least upper bound property and contains Q。