LineIndex* make_index(istream& input, vector<string> const& entries) {
LineIndex* index = new LineIndex;
for(EntryIt p = entries.begin(); p != entries.end(); ++p)
(*index)[*p]; // causes insertion ?
string line, word;
int line_number = 0;
// read a line from input at a time into a string
while(getline(input, line)){
++line_number;
// make an istream from the string
istrstream words(static_cast<const char*>(line.c_str()));
// read a word at a time from string
while(words >> word) {
// use find() on map<string, vector<int>> to see
// if it contains the word already, if it does,
// save the line number in the map's vector
LineIndex::iterator p = index->find(word);
if(p != index->end())
(*p).second.push_back(line_number);
}
}
}
