subroutine addpt(j,nadj,madj,x,y,ntot,eps,nerror)
# Add point j to the triangulation.
# Called by master, dirseg.

implicit double precision(a-h,o-z)
dimension nadj(-3:ntot,0:madj), x(-3:ntot), y(-3:ntot)
logical didswp

# Put the new point in, joined to the vertices of its
# enclosing triangle.
call initad(j,nadj,madj,x,y,ntot,eps,nerror)
if(nerror > 0) return

# Look at each `gap', i.e. pair of adjacent segments
# emanating from the new point; they form two sides of a
# quadrilateral; see whether the extant diagonal of this
# quadrilateral should be swapped with its alternate
# (according to the LOP: local optimality principle).
now = nadj(j,1)
nxt = nadj(j,2)
ngap = 0
repeat {
        call swap(j,now,nxt,didswp,nadj,madj,x,y,ntot,eps,nerror)
	if(nerror > 0) return
        n = nadj(j,0)
        if(!didswp) {         # If no swap of diagonals
                now  = nxt    # move to the next gap.
                ngap = ngap+1
        }
        call succ(nxt,j,now,nadj,madj,ntot,nerror)
	if(nerror > 0) return
}
until(ngap==n)

return
end