/* string processing program using a global file reference - less modular */
	#include <iostream>
	#include <fstream>
	#include <string>
	using namespace std;

    //function prototypes
    void change(string &line);

    //global declarations
	ifstream changesfile;

	int main()
	{
		string line;

        // open input file
		ifstream infile("c:\\bc\\cis1_5\\newpgms\\chapter8\\myinput.txt"); //comment-out for debugging
//        ifstream infile("con");                    //un-comment for debugging
        
        // open output file
//		ofstream outfile("c:\\bc\\cis1_5\\newpgms\\chapter8\\myoutput.txt"); //comment-out for debugging
        ofstream outfile("con");                    //un-comment for debugging
        
		while (getline(infile, line))
		{      
			outfile << line << endl;                //output old line
 			change(line);                           //make changes
			outfile << line << endl;                //output revised line
		}

        infile.close();                             //close input file
        outfile.close();                            //close output file
        
		system("pause");
		return 0;
	}

	/* Function change()
	 * Input:
	 * 	line - a reference to the string to be processed
	 * Globals:
	 * 	changesfile - global reference to the file that contains the replacement pairs
	 * Process:
	 * 	Repeatedly get a new set of replacement strings
	 *	(oldstr & newstr), until there are no more sets of
	 *	changes. Search line for position of oldstr.
	 * 	If oldstr exists, replace oldstr with newstr.
	 * 	Returns when all replacements have been made
	 * Output: 
	 * 	line - the processed string
	 */
	void change(string &line)
	{
		string oldstr, newstr;
		string::size_type pos;

        // open changes file
		changesfile.open("c:\\bc\\cis1_5\\newpgms\\chapter8\\mychanges.txt"); //comment-out for debugging
//		changesfile.open("con");    //un-comment for debugging
		changesfile.clear();                                      //reset EOF flag

		while (getline(changesfile, oldstr))                      //read oldstr
		{
			getline(changesfile, newstr);                         //read newstr
			pos = line.find(oldstr, 0);                           //search for oldstr
			while (pos != line.npos)                              //if oldstr found
			{
				line.replace(pos, oldstr.length(), newstr);       //replace oldstr with newstr
				pos = line.find(oldstr, pos+newstr.length());     //search for oldstr
			}
		}
		changesfile.close();
		return;
	}