Thread: boost tokenizer problem

Hello..

Whenever I compile this code, I get boost compile error, though I have no idea what could be wrong.

Code:

#include <string>
#include <iostream>
#include <boost/tokenizer.hpp>

using namespace std;

int parse(string data) {

	typedef boost::tokenizer <boost::escaped_list_separator<char> > tokenizer;
	tokenizer tokens(data);

	for (tokenizer::iterator it = tokens.begin(); it != tokens.end(); it++) {
		cout << *it << endl;

		cout << *(it - 1) << endl;  //here i want to print the previous iterator (if it exists)
	}

	return 0;
}

Thanks a lot for help

You can't do (it - 1) in the code.

The iterator you are working with will ONLY support ++. Not --, not +, not -.

One solution is to copy the elements out of the tokenizer into a standard container. For example:

Code:

#include <string>
#include <vector>
#include <iostream>
#include <boost/tokenizer.hpp>


int parse(std::string data) {

	typedef boost::tokenizer <boost::escaped_list_separator<char> > tokenizer;
	tokenizer tokens(data);

	std::vector<std::string> vectorTokens;

	std::copy(tokens.begin(),tokens.end(),std::back_inserter(vectorTokens));



	for (std::vector<std::string>::iterator it = vectorTokens.begin(); it != vectorTokens.end(); ++it) {
		std::cout << *it << std::endl;

		std::cout << *(it - 1) << std::endl;  //here i want to print the previous iterator (if it exists)
	}

	return 0;
}

Of course, you need to do something special to handle the very first iteration through the loop, or you'll try to walk off the beginning of the vector with the it-1.

Easier to just save the token for one iteration and print it again.