ADAS Subroutine r8feei

      FUNCTION R8FEEI ( X )
C-----------------------------------------------------------------------
C
C  **************** FORTRAN77 REAL*8 FUNCTION: R8FEEI ******************
C
C  PURPOSE: EVALUATES EXP(X)E1(X) WHERE E1 IS THE 1ST EXPONENTIAL
C           INTEGRAL
C
C  NOTE:    EXACT DUPLICATE IN OPERATION TO EEI.
C
C  REFERENCE:
C
C  CALLING PROGRAM: GENERAL USE
C
C  FUNCTION:
C
C  INPUT:  (R*8)  X       = INPUT PARAMETER
C
C  OUTPUT: (R*8)  R8FEEI  = FUNCTION NAME
C
C          (R*8)  DHALF   = PARAMETER = 0.5
C          (R*8)  CX0     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CX1     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CX2     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CX3     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CX4     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CX5     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CY0     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CY1     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CY2     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CY3     = PARAMETER = EQUATION CONSTANT
C          (R*8)  CY4     = PARAMETER = EQUATION CONSTANT
C          (R*8)  C0N     = PARAMETER = EQUATION CONSTANT
C          (R*8)  C1N     = PARAMETER = EQUATION CONSTANT
C          (R*8)  C2N     = PARAMETER = EQUATION CONSTANT
C          (R*8)  C3N     = PARAMETER = EQUATION CONSTANT
C          (R*8)  C1D     = PARAMETER = EQUATION CONSTANT
C          (R*8)  C2D     = PARAMETER = EQUATION CONSTANT
C          (R*8)  C3D     = PARAMETER = EQUATION CONSTANT
C          (R*8)  C4D     = PARAMETER = EQUATION CONSTANT
C
C          (R*8)  A       = GENERAL VARIABLE
C          (R*8)  Y       = GENERAL VARIABLE
C          (R*8)  Z       = GENERAL VARIABLE
C
C ROUTINES: NONE
C
C AUTHOR:   PAUL E. BRIDEN (TESSELLA SUPPORT SERVICES PLC)
C           K1/0/81
C           JET EXT. 4569
C
C DATE:     18/09/90
C
C VERSION  : 1.2                          
C DATE     : 20-12-2001
C MODIFIED : Martin O'Mullane
C               - Removed mainframe listing information beyond column 72.
C
C VERSION  : 1.3                          DATE: 17-4-07
C MODIFIED : HUGH SUMMERS
C            - COMPLETED COMMENT BLOCK DESCRIPTION
C
C-----------------------------------------------------------------------
C-----------------------------------------------------------------------
      REAL*8              X