/**
 * A FileReader object will read tokens from an input file.  The name of
 * the input file is given when the constructor is run. The lone method,
 * nextToken(), will return the next token in the file as a String.  
 * 
 * @author Chris Fernandes
 * @version 10/26/08
 */
import java.io.*;

public class FileReader 
{
    private StreamTokenizer st;     //file descriptor

    /** non-default constructor.
     * 
     *  @param fileName full path to input file.
     *  Example: "C:/project 6/input.txt"
     *  Be sure to use forward slashes to specify folders.  And
     *  don't forget the quotes (it's a String!)
     */
    public FileReader(String fileName) 
    {
        try {
	    st = new StreamTokenizer(
		     new BufferedReader(
			 new InputStreamReader(
			     new FileInputStream(fileName))));
        } catch (IOException e) {}

        st.resetSyntax();                         // remove default rules                
        st.ordinaryChars(0, Character.MAX_VALUE); // turn on all chars
        st.whitespaceChars(0, 39);                   // ignore unprintables &
        st.whitespaceChars(95, Character.MAX_VALUE); // everything after ^
    }

    /** Returns the next valid token from the input file.
     *  Possible tokens are "+", "-", "*", "/", "^", "(", ")",
     *  ";", operands (capital letters), and the special 
     *  token "EOF" which is returned when the
     *  end of the input file is reached.
     * 
     *  @return next valid token or "EOF"
     */
    public String nextToken() 
    {
        try {
	    while (st.nextToken() != StreamTokenizer.TT_EOF) {
		if (st.ttype < 0) {
		    return st.sval;
		} else {
		    return String.valueOf((char)st.ttype);
		}
	    }
	    return "EOF";
        } catch (IOException e) {}
        return "error";
    }
}