How do i break a loop at set values to NaN

I need to break a loop when i reach values if alpha<-pi or apha>pi and set values for alpha and x(direction) to NaN, this is not working, please adivse

if alpha(i)<(-pi)||alpha(i)>(pi)   
      
        break
        x(i+1:end)=NaN;
        alpha(i+1:end)=NaN;
end

Answer 1

[per isakson]

Try

if alpha(i)<(-pi)||alpha(i)>(pi)   
        x(i+1:end)=NaN;
        alpha(i+1:end)=NaN;
        break
end