# cpsi.f

          COMPLEX FUNCTION CPSI (ZIN)
    C***BEGIN PROLOGUE  CPSI
    C***PURPOSE  Compute the Psi (or Digamma) function.
    C***LIBRARY   SLATEC (FNLIB)
    C***CATEGORY  C7C
    C***TYPE      COMPLEX (PSI-S, DPSI-D, CPSI-C)
    C***KEYWORDS  DIGAMMA FUNCTION, FNLIB, PSI FUNCTION, SPECIAL FUNCTIONS
    C***AUTHOR  Fullerton, W., (LANL)
    C***DESCRIPTION
    C
    C PSI(X) calculates the psi (or digamma) function of X.  PSI(X)
    C is the logarithmic derivative of the gamma function of X.
    C
    C***REFERENCES  (NONE)
    C***ROUTINES CALLED  CCOT, R1MACH, XERMSG
    C***REVISION HISTORY  (YYMMDD)
    C   780501  DATE WRITTEN
    C   890531  Changed all specific intrinsics to generic.  (WRB)
    C   890531  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***END PROLOGUE  CPSI