Here is a solution to the expression code generation problem

from Assignment 5. The one posted earlier by David Cimbala is

incorrect. The code you need to write for Assignment 7 is not much

more than this.

- Professor Pingali

class Parser
 
{
 private static CS211In fpe;
 private static CS211Out outfile;
 private String result;

 // this is our recursive descent parsing routine
 // the fpe is assumed to be correct, no error checking in this version
 public static String evalFpe()
 { String code = "";
         switch (fpe.peekAtKind()) {
         case fpe.INTEGER: {
                 int num = fpe.getInt();
                 code = "PUSHIMM " + num + "\n"; // string concatenation
                 break;
                 }

         case fpe.OPERATOR: {
                 char op = fpe.getOp(); // get the left parentheses
                 String arg1 = evalFpe(); // recursive call to deal with
                                          // first argument
                 op = fpe.getOp(); // get the arithmetic operator
                 String arg2 = evalFpe(); // deal with second argument
                 char op2 = fpe.getOp(); // move past right parentheses
                 String arith = "";
                 switch (op) {
                 case '+': arith = "ADD " + "\n"; break;
                 case '-': arith = "SUB " + "\n"; break;
                 case '*': arith = "TIMES " + "\n"; break;
                  }
                 code = arg1 + arg2 + arith;
                 break;
	 }
                 
        
	 }
 return code;
 }

 public static void main(String[] args)
 {
        if (args.length == 1 )
                fpe = new CS211In(args[0]); // cmd line entry
        else {
                System.out.println("Usage: Parser ");
                return;
        }

        String result = evalFpe() + "STOP " + "\n"; // last SaM cmd
        CS211Out outfile = new CS211Out("exp.sam");
        outfile.println(result);
        outfile.close();
 }
}