>>554より (引用開始) https://en.wikipedia.org/wiki/Cauchy_sequence Cauchy sequence In real numbers For any real number r, the sequence of truncated decimal expansions of r forms a Cauchy sequence. For example, when r=π, this sequence is (3, 3.1, 3.14, 3.141, ...). The mth and nth terms differ by at most 10^(1−m) when m < n, and as m grows this becomes smaller than any fixed positive number ε. (引用終り)
つまり、有理コーシー列ならば 表現の自由度が大きいから ”For any real number r, the sequence of truncated decimal expansions of r forms” を使おうってことだ
