function [white]=gasdev;
% [white]=gasdev;
R=2;
while (R >=1)
   V1=2*rand-1;
   V2=2*rand-1;
   R=V1*V1+V2*V2;
   if (R<1)
      FAC=sqrt(-2*log(R)/R);
      gasdev=V2*FAC;
      white=gasdev;
   end
end
