//-----------------------------------------------------------
//  Purpose:    Demonstrate how strings can be broken into tokens.
//  Author:     John Gauch
//-----------------------------------------------------------

#include <string>
#include <iostream>
using namespace std;

//-----------------------------------------------------------
// Function that extracts space separated tokens from input.
// Returns true when token is found, and false when not found.
//-----------------------------------------------------------
bool get_token(string & input, string & token)
{
   // Find start of token
   unsigned int start = 0;
   while ((start < input.length()) && (input.at(start) == ' '))
      start++;

   // Find end of token
   unsigned int end = start;
   while ((end < input.length()) && (input.at(end) != ' '))
      end++;

   // Extract token from input
   token = input.substr(start, end - start);
   input = input.substr(end, input.length() - end);
   return (token.length() > 0);
}

//-----------------------------------------------------------
// Main program for testing.
//-----------------------------------------------------------
int main()
{
   string input = " num = 42 17 +  ";
   string token = "";
   cout << "input = '" << input << "'\n";
   while (get_token(input, token))
      cout << "token = '" << token << "'\n";
}