MATLAB: Fill part of vector

Question

 I have a=[1 2 5 4 2 7 4 8 2 3](10 values),b=[0 1 2 3],I want to fill a so that
 a=[0 1 2 3 0 0 0 0 0 0],

Answer 1

There's nothing left so there's no point in doing anything except sotoo--

a=0; a(1:length(b))=b;
a=[b zeros(1,length(a)-length(b)];

An essentially innumerable ways to get there, choose one and go on.