C#> polyn.dc2
C
CName:       POLYN
C
C
CPurpose:    POLYN  computes the value of an N-component polynomial
C            DPOLYN computes the partial derivatives of that polynomial
C
CFiles:      polyn.dc2,polyn.shl
C
CAuthor:     Peter Roelfsema
C
C
CCall:
C
C    PX=POLYN(X,PAR,NPAR)
C
C	   Input parameters:
C          X     -R   -running coordinate.
C          PAR   -R   -array defined as follows: PAR(0:NPAR) that
C			  contains the parameters for the polynomial:
C	                  PAR(n)-polynomial coefficient for X**n.
C          NPAR  -I   -degree of the polynomial.
C
CUse:
C            POLYN gives the value of a multi-component polynomial.
C            Note that the polynomial is defined as the following
C            summation:
C
C                 PX = 0  FOR N=0 TO NPAR ( PX = PX + PAR(N) * X**N )
C
C            POLYN does not check for floating overflows in X**N, you
C            will have to worry about that yourself.
C
C
CUpdate History:
C   8- 7-85-PRR.-original document
C  16- 6-86-PRR.-converted for VAX8600.
C  10- 9-92-PRR.-converted to new GIPSY
C#<
C
C@ real function polyn( real , real , integer )
C@ subroutine dpolyn( real , real , real , integer )
C               
      REAL FUNCTION POLYN(X,PAR,NPAR)


N.X-coordinate for which the polynomial is to be calculated
      REAL      X
N.parameters of the polynomial
      REAL      PAR(*)
N.partial derivatives
      REAL      DERIV(*)
N.buffer variables
      REAL      POLY,XI

N.number of parameters
      INTEGER   NPAR
N.loop counter
      INTEGER   I


N.zero level
      POLY=PAR(1)
N.initialise for loop
      XI=1.0
N.loop on parameters
      FOR I=2,NPAR
N.next power of X
      XI=XI*X
N.add to POLY
      POLY=POLY+PAR(I)*XI
      CFOR
N.transfer to function
      POLYN=POLY
      RETURN

C
C#> dpolyn.dc2
C
CName:       DPOLYN
C
C
CPurpose:    DPOLYN computes the partial derivatives of that polynomial
C
CFiles:      dpolyn.dc2,polyn.shl
C
CAuthor:     Peter Roelfsema
C
CCall:
C
C    CALL DPOLYN(X,PAR,DERIV,NPAR)          ( entry point in POLYN )
C
C        Input parameters:
C             X     -R   -running coordinate.
C             PAR   -R   -array  defined  as follows: PAR(0:NPAR) that
C                         contains the parameters for the polynomial:
C                         PAR(n)-polynomial coefficient for X**n.
C             NPAR  -I   -degree of the polynomial.
C        Output parameters:
C             DERIV -R   -array defined as follows: DERIV(0:NPAR) that
C                         contains the partial derivatives of the
C                         polynomial with respect to the parameters:
C                         DERIV(n)-partial derivative of coefficient for
C                         X**n ( i.e. X**n ).
C
C
CUse:
C               DPOLYN gives the partial derivatives for the gaussian.
C               Note that the polynomial is defined as the following
C               summation:
C
C                 PX = 0  FOR N=0 TO NPAR ( PX = PX + PAR(N) * X**N )
C
C               DPOLYN does not check for floating overflows in X**N, you
C               will have to worry about that yourself.
C#<
C
      ENTRY DPOLYN(X,PAR,DERIV,NPAR)

N.zero level-derivative
      DERIV(1)=1.0
N.initialise for loop
      XI=1.0
N.loop on all parameters
      FOR I=2,NPAR
N.next power of X
      XI=XI*X
N.set part. derivative
      DERIV(I)=XI
      CFOR
      RETURN
      END