Problem Statement

Create a function,   or show a built-in function,   to count the number of non-overlapping occurrences of a substring inside a string. The function should take two arguments:

It should return an integer count. The matching should yield the highest number of non-overlapping matches. In general, this essentially means matching from left-to-right or right-to-left   (see proof on talk page).

Let's start with the solution:

subvec(v,u)={
	my(i=1,s);
	while(i+#u<=#v,
		for(j=1,#u,
			if(v[i+j-1]!=u[j], i++; next(2))
		);
		s++;
		i+=#u
	);
	s
};
substr(s1,s2)=subvec(Vec(s1),Vec(s2));
substr("the three truths","th")
substr("ababababab","abab")