/** Parser for Assignment 2 */

import java.io.*;
import java.util.*;

/** Each parser object in this class contains an embedded lexer which contains an embedded input stream.  The
  * class include a parse() method that will translate the program text in the input stream to the corresponding
  * AST assuming that the program text forms a syntactically valid Jam program.
  */
class Parser {
  
  private Lexer in;

  . . .
  
  Parser(Lexer i) {
    in = i;
    initParser();
  }
  
  Parser(Reader inputStream) { this(new Lexer(inputStream)); }
  
  Parser(String fileName) throws IOException { this(new FileReader(fileName)); }
  
  Lexer lexer() { return in; }
  
  private void initParser() {
    . . .
  }
  
  /** Parses the program text in the lexer bound to 'in' and returns the corresponding AST. 
    * @throws ParseException if a syntax error is encountered (including lexical errors). 
    */
  public AST parse() throws ParseException {
    . . .
  }
  
  /** Parses:
    *     <exp> :: = if <exp> then <exp> else <exp>
    *              | let <prop-def-list> in <exp>
    *              | map <id-list> to <exp>
    *              | <term> { <biop> <exp> }
    * 
    * @return  the corresponding AST.
    */
  private AST parseExp() {
    . . .
  }
  
  . . .
}