splitting input from cin

[alfie nsugh]

#include <iostream>
#include <vector>
#include <cctype>

using std::string;
using std::vector;
using std::cin;
using std::cout;
using std::endl;

vector<string> split(const string& s)
{
	vector<string> ret;
	typedef string::size_type string_size;
	string_size i = 0;

	//invariant: we have processed characters [original value of i, i)
	while (i != s.size()){
		// ignore leading blanks
		// invariant: characters in range [original i, current i)
	while (i != s.size() && isspace(s[i]))
		++i;

	// find end of next word
	string_size j = i;
	// invariant: none of the characters in range [original j, current j)
	while (j != s.size() && !isspace(s[j]))
		j++;
		// if we found some nonwhitespace characters
		if(i != j){
			//copy from s starting at i and taking j-i chars
			ret.push_back(s.substr(i, j - i));
			i = j;
		}
	}
	return ret;
}

int main(){
	string s;

	//read and split each line of input
	while(getline(cin, s)){
		vector<string> v = split(s);

		//write each word in v
		for(vector<string>::size_type i = 0; i != v.size(); ++i)
			cout << v[i] << endl;
	}
	return 0;
}

Why does it work when you do vector<string> v = split(s); what I mean is,
why doesn't the first index of the vector v get overwritten by the next ret.
Also, I thought that the function split would only get the first word of the sentence but apparently all words are returned.

I hope my questions make a bit of sense, I'm aware that I'm probably just having some misconceptions but I cannot figure out what those are.

[tpb]

split creates and returns an entire vector (called ret in split) which is assigned to v and contains all the words. That's how split functions usually work. If it was returning a word at a time it would be more of a tokenizing function.

And why would the "first index" of v get the return? The first index is v[0], not v. v is the entire vector.

[alfie nsugh]

I get it now, thank you so much tpb