REAL FUNCTION XSPSI(A,IPSIK,IPSIX)
C***BEGIN PROLOGUE  XSPSI
C***REFER TO  XSLEGF
C***ROUTINES CALLED  (NONE)
C***DATE WRITTEN   820728   (YYMMDD)
C***REVISION DATE  871119   (YYMMDD)
C***CATEGORY NO.  C7c
C***KEYWORDS  PSI FUNCTION
C***AUTHOR  SMITH, JOHN M. (NBS AND GEORGE MASON UNIVERSITY)
C***PURPOSE  TO COMPUTE VALUES OF THE PSI FUNCTION FOR XSLEGF.
C        FUNCTION PSI(A,IPSIK,IPSIX) RETURNS THE VALUE OF THE
C        DIGAMMA ( OR PSI ) FUNCTION OF THE ARGUMENT A TO THE
C        CALLING ROUTINE.
C***REFERENCES  OLVER AND SMITH,J.COMPUT.PHYSICS,51(1983),N0.3,502-518.
C***END PROLOGUE  XSPSI