DOUBLE PRECISION FUNCTION DCHFIV(X1,X2,F1,F2,D1,D2,A,B,IERR)
C***BEGIN PROLOGUE  DCHFIV
C***REFER TO  DPCHIA
C***ROUTINES CALLED  XERROR
C***REVISION DATE  870707   (YYMMDD)
C***DESCRIPTION
C
C          DCHFIV:  Cubic Hermite Function Integral Evaluator.
C
C     Called by  DPCHIA  to evaluate the integral of a single cubic (in
C     Hermite form) over an arbitrary interval (A,B).
C
C ----------------------------------------------------------------------
C
C  Calling sequence:
C
C        INTEGER  IERR
C        DOUBLE PRECISION  X1, X2, F1, F2, D1, D2, A, B
C        DOUBLE PRECISION  VALUE, DCHFIV
C
C        VALUE = DCHFIV (X1, X2, F1, F2, D1, D2, A, B, IERR)
C
C   Parameters:
C
C     VALUE -- (output) value of the requested integral.
C
C     X1,X2 -- (input) endpoints if interval of definition of cubic.
C           (Must be distinct.  Error return if not.)
C
C     F1,F2 -- (input) function values at the ends of the interval.
C
C     D1,D2 -- (input) derivative values at the ends of the interval.
C
C     A,B -- (input) endpoints of interval of integration.
C
C     IERR -- (output) error flag.
C           Normal return:
C              IERR = 0 (no errors).
C           "Recoverable errors":
C              IERR = -1  if X1.EQ.X2 .
C                (VALUE has not been set in this case.)
C
C***END PROLOGUE  DCHFIV