A class of smoothing fit and evaluation should be written:

class regrid:
    put the data in the class (x, y, z)
    user controls its behavior by iopt, s, kx, ky, nxest, nyest
    working space is allocated by the class itself
    the coefficients, knots calculated are stored in the class
    
    routines:
	error: reports the fitness fp
	knot: return knots
	eval: eval at any point, array in, array out, by bispev
	
    raise exception if error happened in the underlying fortran routine


class surfit:
    data in (x, y, z), its length m
    user controls its behavior by iopt, s, kx, ky, nxest, nyest, and w
    system provide eps
    the coefficients, knots are stored in the class

    routines:
	error: return fp
	knot: return knots
	eval: eval

    raise exception if error happened in the underlying fortran routine

