function [y]=Qfunct(x)
% [y]=Qfunct(x)
%      QFUNCT evaluates the Q-function.
%      y=1/sqrt(2*pi)*integral from x to inf of exp(-t^2/2) dt.
%      y=(1/2)*erfc(x/sqrt(2)).
y=(1/2)*erfc(x/sqrt(2));