import pattpack.ast_extr.*;
import pattpack.expr_extr.*;
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) {
	VarFactory vf = VarFactory.getInstance ();
	Statement factorial = new Compound (
	    new Assignment (vf.makeVar ("fact", 1), vf.makeVar ("1", 1)),
	    new While (new Gt (vf.makeVar ("n", 2),
			       vf.makeVar ("1", 2)), new Compound (
      	        new Assignment (vf.makeVar ("fact", 3),
				new Mul (vf.makeVar ("fact", 3),
					 vf.makeVar ("n", 3))),
	        new Assignment (vf.makeVar ("n", 4),
				new Sub (vf.makeVar ("n", 4),
					 vf.makeVar ("1", 4))))));
	factorial.print (System.out, 0);
	System.out.println ();
    }
}