8FUNCTIONS: ifird - CYANA function

Synopsis: ifird(<integer>) = <integer>

Number of the first dihedral angle belonging to the residue n.

The function returns the original index of the first (rotatable or
fixed) dihedral angle that belongs to the residue with the given index,
or the special value ifird(nr+1) = nd+1.

This function is useful, for instance, to construct a loop over all
atoms of a given residue, i:

  do j ifird(i) ifird(i+1)-1
    print "Angle $dnam(idord(j)) of residue $rnam(i) $rnum(i)"
  end do
