EV2PPF
      SUBROUTINE EV2PPF(P,GAMMA,PPF)
  
PURPOSE--This subroutine computes the percent point function
         value for the extreme value type 2 distribution with
         single precision tail length parameter = GAMMA.  The
         extreme value type 2 distribution used herein is
         defined for all non-negative X, and has the probability
         density function
         F(X) = GAMMA * (X**(-GAMMA-1)) * EXP(-(X**(-GAMMA))).
         note that the percent point function of a distribution
         is identically the same as the inverse cumulative
         distribution function of the distribution.
INPUT  ARGUMENTS--P      = The single precision value (between
                           0.0 and 1.0 (exclusively) at which
                           the percent point function is to be
                           evaluated.
                --GAMMA  = The single precision value of the
                           tail length parameter.  GAMMA
                           should be positive.
OUTPUT ARGUMENTS--PPF    = The single percision percent point
                           function value.
OUTPUT--The single precision percent point function value PPF
        for the extreme value type 2 distribution with tail
        length parameter value = GAMMA.
PRINTING--None unless an input argument error condition exists.
RESTRICTIONS--GAMMA should be positive.
            --P should be between 0.0 and 1.0 (exclusively).
OTHER DATAPAC   SUBROUTINES NEEDED--None.
FORTRAN LIBRARY SUBROUTINES NEEDED--ALOG.
MODE OF INTERNAL OPERATIONS--Single Precision.
LANGUAGE--ANSI FORTRAN.
REFERENCES--Johnson and Kotz, Continuous Univariate
            Distributions--1, 1970, Pages 272-295.
WRITTEN BY--James J. Filliben
            Statistical Engineering Laboratory (205.03)
            National Bureau of Standards
            Gaithersburg, MD  20899
            Phone--  301-921-2315
ORIGINAL VERSION--November  1975.