Finding the fundamental unit of a real quadratic field
This is a program for finding the fundamental unit η of Q(√d), where d is a squarefree positive integer. It is a BCmath version of the BC program unit.
The algorithm is based on K. Rosen, Elementary number theory and its applications, p.382, B.A. Venkov, Elementary Number theory, p.62 and D. Knuth, Art of computer programming, Vol.2, p.359, with Pohst's trick of using half the period.
η=x+yω, where ω=(1 +√d)/2 if d ≡ 1 (mod 4), ω = √d otherwise.
Last modified 2nd June 2006
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