include	<gset.h>

define	MSIZE		4.		# Mark size

# SPADDN -- Add a node for cubic spline fit.

procedure spaddn (gp, wx, wy, x, y, npts)

pointer	gp				# GIO pointer
real	wx				# X point to insert	
real	wy				# Y point to insert	
double	x[npts]				# Independent variable
double	y[npts]				# Dependent variable
int	npts				# Number of points

int	i, j

begin
	# Find the place to insert the new point.
	if (x[1] < x[npts])
	    for (i = npts; (i > 0) && (wx < x[i]); i = i - 1)
		;
	else
	    for (i = npts; (i > 0) && (wx > x[i]); i = i - 1)
		;

	# Shift the data to insert the new point.
	for (j = npts; j > i; j = j - 1) {
	    x[j+1] = x[j]
	    y[j+1] = y[j]
	}

	# Add the new point and increment the number of points.
	i = i + 1
	x[i] = wx
	y[i] = wy
	npts = npts + 1

	# Mark the point
	call gmark (gp, real (x[i]), real (y[i]), GM_PLUS, MSIZE, MSIZE)
end