 
      DOUBLE PRECISION FUNCTION DGAMIC(A,X)
C***BEGIN PROLOGUE  DGAMIC
C***DATE WRITTEN   770701   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C7E
C***KEYWORDS  COMPLEMENTARY,COMPLEMENTARY INCOMPLETE GAMMA FUNCTION,
C             DOUBLE PRECISION,GAMMA,GAMMA FUNCTION,SPECIAL FUNCTION
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Calculates the d.p. complementary incomplete Gamma function
C***DESCRIPTION
C
C Evaluate the complementary incomplete gamma function
C
C DGAMIC = integral from T = X to infinity of EXP(-T) * T**(A-1.)  .
C
C DGAMIC is evaluated for arbitrary real values of A and for non-
C negative values of X (even though DGAMIC is defined for X .LT. 0.0),
C except that for X = 0 and A .LE. 0.0, DGAMIC is undefined.  The
C function and both arguments are double precision.
C
C      A slight deterioration of 2 or 3 digits accuracy will occur when
C DGAMIC is very large or very small in absolute value, because log-
C arithmic variables are used.  Also, if the parameter A is very close
C to a negative INTEGER (but not a negative integer), there is a loss
C of accuracy, which is reported if the result is less than half
C machine precision.
C
C Ref. -- W. Gautschi, An Evaluation Procedure for Incomplete Gamma
C Functions, ACM Trans. Math. Software.
C***REFERENCES  (NONE)
C***ROUTINES CALLED  D1MACH,D9GMIC,D9GMIT,D9LGIC,D9LGIT,DINT,DLGAMS,
C                    DLNGAM,XERCLR,XERROR
C***END PROLOGUE  DGAMIC
 
 
