SLATEC Routines --- DPSI ---

*DECK DPSI
      DOUBLE PRECISION FUNCTION DPSI (X)
C***BEGIN PROLOGUE  DPSI
C***PURPOSE  Compute the Psi (or Digamma) function.
C***LIBRARY   SLATEC (FNLIB)
C***CATEGORY  C7C
C***TYPE      DOUBLE PRECISION (PSI-S, DPSI-D, CPSI-C)
C***KEYWORDS  DIGAMMA FUNCTION, FNLIB, PSI FUNCTION, SPECIAL FUNCTIONS
C***AUTHOR  Fullerton, W., (LANL)
C***DESCRIPTION
C
C DPSI calculates the double precision Psi (or Digamma) function for
C double precision argument X.  PSI(X) is the logarithmic derivative
C of the Gamma function of X.
C
C Series for PSI        on the interval  0.          to  1.00000E+00
C                                        with weighted error   5.79E-32
C                                         log weighted error  31.24
C                               significant figures required  30.93
C                                    decimal places required  32.05
C
C
C Series for APSI       on the interval  0.          to  1.00000E-02
C                                        with weighted error   7.75E-33
C                                         log weighted error  32.11
C                               significant figures required  28.88
C                                    decimal places required  32.71
C
C***REFERENCES  (NONE)
C***ROUTINES CALLED  D1MACH, DCOT, DCSEVL, INITDS, XERMSG
C***REVISION HISTORY  (YYMMDD)
C   770601  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   890911  Removed unnecessary intrinsics.  (WRB)
C   890911  REVISION DATE from Version 3.2
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900315  CALLs to XERROR changed to CALLs to XERMSG.  (THJ)
C   900727  Added EXTERNAL statement.  (WRB)
C   920618  Removed space from variable name.  (RWC, WRB)
C***END PROLOGUE  DPSI