SUBROUTINE CDCLFN (
*
*  inputs
*
     :                  VAR, COEFF,
*
*  outputs
*
     :                  F0, FVAR, FCOEFF)
*
*  Module number:
*
*  Module name:
*
*  Keyphrase:
*  ----------
*  Calculate functional values and derivatives of a circle.
*
*  Description:
*  ------------
*  For the function:
*
*       F = (X - x0)^2 + (Y - y0)^2 - r^2
*
*  calculate the functional value F0, for given x0, y0, r, X, and Y.  Also
*  calculate the partial derivatives of F relative to x0, y0, and r
*  (coefficents) and X, and Y (variables).
*
*  COEFF(1) = x0, COEFF(2) = y0, COEFF(3) = r, VAR(1) = X, VAR(2) = Y
*
*  FORTRAN name: CDCLFN.FOR
*
*  Keywords of accessed files and tables:
*  --------------------------------------
*  Name                         I/O     Description / Comments
*       None
*
*  Subroutines Called:
*  -------------------
*  CDBS:
*       None
*  SDAS:
*       None
*  Others:
*       None
*
*  History:
*  --------
*  Version      Date        Author          Description
*     1       02-16-87     J.-C. HSU        design and coding
*
*-------------------------------------------------------------------------------
*
*== input:
*                                       --observed variables at a given point
*                                       --(e. g. X and Y coordinates)
        DOUBLE PRECISION        VAR(*),
*                                       --coefficients in the given function
     :                          COEFF(*)
*
*== output:
*                                       --functional value
        DOUBLE PRECISION        F0,
*                                       --partial derivativeS relative to the
*                                       --variables and coefficients
     :                          FVAR(*), FCOEFF(*)
*
*------------------------------------------------------------------------------
*
*  functional value
*
        F0 = (VAR(1) - COEFF(1)) ** 2 + (VAR(2) - COEFF(2)) ** 2 - 
     :       COEFF(3) ** 2
*
*  partial derivatives relative to the variables
*
        FVAR(1) = 2.D0 * (VAR(1) - COEFF(1))
*
        FVAR(2) = 2.D0 * (VAR(2) - COEFF(2))
*
*  partial derivatives relative to the coefficients
*
        FCOEFF(1) = -FVAR(1)
*
        FCOEFF(2) = -FVAR(2)
*
        FCOEFF(3) = -2.D0 * COEFF(3)
*
        RETURN
        END