use Pair instead of cpair in Fixrec_ex.thy
use Pair instead of cpair in Fixrec_ex.thy

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle