[p]=c4_pos(m)

function [p]=c4_pos(m)
%
%  It produces a Poisson mass function with mean  m
%  It stops at the term when  CDF > .9999
% 
x=exp(-m); s=x; p=[x]; n=1;  
while  s < .9999      
x=x*m/n; p=[p x]; s=s+x; n=n+1; 
end