[boost] StringAlgo::split issue

Hi, I used the split function on the following string: vector<string> tokens; string str= "( 448 448 64 ) ( 448 0 64 ) ( 0 448 64 ) name 0 0 0 0.5 0.5 0 0 0"; split( tokens, str, is_any_of( ()), token_compress_on ); // I pass 'space' , '(' and ')' into is_any_of() I was supposed to get 18 tokens. The first nine values, the string "name" and the remaining eight digits. "split" always returns a string vector containing 19 tokens, where the first element of the vector is an empty string. Why does the function insert empty strings into the collection? Can I use split to obtain the 18 wanted tokens? -Dirk