*DECK DF1F
      DOUBLE PRECISION FUNCTION DF1F (X)
C***BEGIN PROLOGUE  DF1F
C***PURPOSE  Subsidiary to
C***LIBRARY   SLATEC
C***AUTHOR  (UNKNOWN)
C***ROUTINES CALLED  (NONE)
C***REVISION HISTORY  (YYMMDD)
C   ??????  DATE WRITTEN
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C***END PROLOGUE  DF1F
      DOUBLE PRECISION X,X1,Y
C***FIRST EXECUTABLE STATEMENT  DF1F
      X1 = X+0.1D+01
      DF1F = 0.5D+01/X1/X1
      Y = 0.5D+01/X1
      IF(Y .GT. 3.1415926535897932D0) DF1F = 0.0D0
      RETURN
      END
