import pattpack.ast_none.*;
import pattpack.expr_none.*;
import java.io.*;

/**
 *  Driver for a Composite pattern example.
 *  Composite objects are programs in a simple "while" language
 *  defined by the following syntax:
 *  <PRE>
 *      Statement   ::= Assignment | Conditional | While | Compound
 *      Assignment  ::= Var = Expr
 *      Conditional ::= if Expr then Statement else Statement
 *      While       ::= while Expr do Statement
 *      Compound    ::= begin Statement; ...; Statement end
 *  </PRE>
 *  The main method constructs and pretty prints the following
 *  program
 *  <PRE>
 *      begin
 *        fact = 1;
 *        while (n > 1) do
 *          begin
 *            fact := fact * n;
 *            n := n - 1
 *          end
 *      end
 *  </PRE>
 */
public class Main {
    /** Usual entry point. Constructs and pretty prints an example program. */
    public static void main (String [] arg) {
	Statement factorial = new Compound (
	    new Assignment (new Variable ("fact"), new Variable ("1")),
	    new While (new Gt (new Variable ("n"),
			       new Variable ("1")), new Compound (
      	        new Assignment (new Variable ("fact"),
				new Mul (new Variable ("fact"),
					 new Variable ("n"))),
	        new Assignment (new Variable ("n"),
				new Sub (new Variable ("n"),
					 new Variable ("1"))))));
	factorial.print (System.out, 0);
	System.out.println ();
    }
}