For definition of semicomputable, see this . In fact,it is not true that every Cauchy sequence for completion of rationals is semicomputable, we can not complete rationals by semicomputable Cauchy sequences.

My question:

1, how could in Constructivism way based on Cauchy sequence we complete the rational number system?

2, Since we complete rational number system in several ways like Cauchy seqence,Dedekind cut or even by continued fraction, what is the common idea among them?