Q:

Boost::tokenizer comma separated (c++)

Should be an easy one for you guys.....
I'm playing around with tokenizers using Boost and I want create a token that is comma separated.   here is my code:
    string s = "this is, , ,  a test";
boost::char_delimiters_separator<char> sep(",");
boost::tokenizer<boost::char_delimiters_separator<char>>tok(s, sep);

for(boost::tokenizer<>::iterator beg= tok.begin(); beg!=tok.end(); ++beg)
{
    cout << *beg << "\n";
}

The output that I want is:
This is

 a test

What I am getting is:
This
is
,
,
,
a
test

UPDATED

A:

You must give the separator to tokenizer!
boost::tokenizer<boost::char_delimiters_separator<char>>tok(s, sep);

Also, replace the deprecated char_delimiters_separator with char_separator:
string s = "this is, , ,  a test";
boost::char_separator<char> sep(",");
boost::tokenizer< boost::char_separator<char> > tok(s, sep);
for(boost::tokenizer< boost::char_separator<char> >::iterator beg = tok.begin(); beg != tok.end(); ++beg)
{
    cout << *beg << "\n";
}

Please note that there is also a template parameter mismatch: it's good habit to typedef such complex types: so the final version could be:
string s = "this is, , ,  a test";
boost::char_separator<char> sep(",");
typedef boost::tokenizer< boost::char_separator<char> > t_tokenizer;
t_tokenizer tok(s, sep);
for (t_tokenizer::iterator beg = tok.begin(); beg != tok.end(); ++beg)
{
    cout << *beg << "\n";
}

