Pass II Macro Processor Implementation

Problem Statement

Design suitable data structures and implement Pass-II of a two pass macro processor using OOP features in Java/C++. The output of Pass-I (MNT, MDT, ALA & Intermediate code file without any macro definitions) should be input for Pass-II.

Java Code Implementation

1. MNTEntry Class

public class MNTEntry {
    int index;
    String name;
    int mdtIndex;

    MNTEntry(int index, String name, int mdtIndex) {
        this.index = index;
        this.name = name;
        this.mdtIndex = mdtIndex;
    }
}

2. Pass2Macro Class

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Pass2Macro {
    
        // Hard-coded MNT
        static List MNT = Arrays.asList(
                new MNTEntry(1, "INCR", 0), // MDT index where INCR starts
                new MNTEntry(2, "DECR", 3)  // MDT index where DECR starts
        );

        // Hard-coded MDT
        static List MDT = Arrays.asList(
                "ADD AREG,#0",   // INCR first line
                "SUB BREG,#1", // INCR second line
                "MEND",          
                "SUB AREG,#0",   // DECR first line
                "ADD BREG,#1",   // DECR second line
                "MEND"
        );

        // Hard-coded ALA (macro invocations and actual arguments)
        static Map> ALA = new HashMap<>();
        static {
            ALA.put("INCR", Arrays.asList("A", "B"));
            ALA.put("DECR", Arrays.asList("X", "Y"));
        }

        public static void main(String[] args) {
            // Example program (input with macro calls)
            String[] program = {
                    "START 100",
                    "INCR A,B",
                    "MOVER CREG,=2",
                    "DECR X,Y",
                    "END"
            };

            List expanded = pass2(program);

            System.out.println("----- EXPANDED CODE -----");
            for (String line : expanded) {
                System.out.println(line);
            }
        }

        // PASS 2: Expand macros using MNT, MDT, and ALA
        static List pass2(String[] program) {
            List output = new ArrayList<>();

            for (String line : program) {
                line = line.trim();
                if (line.isEmpty()) continue;

                String[] parts = line.split("[ ,]+"); // START 100

                // Check if this is a macro invocation/call
                MNTEntry found = null;
                for (MNTEntry e : MNT) {
                    if (e.name.equals(parts[0])) {
                        found = e;
                        break;
                    }
                }

                if (found != null) {
                    // Get actuals from ALA
                    List actuals = ALA.get(parts[0]);

                    // Expand MDT lines starting from mdtIndex until next MEND or next macro
                    int index = found.mdtIndex;
                    while (index < MDT.size() && !MDT.get(index).equals("MEND")) {
                        String expLine = MDT.get(index);
                        for (int i = 0; i < actuals.size(); i++) {
                            expLine = expLine.replace("#" + i, actuals.get(i));
                        }
                        output.add(expLine);
                        index++;
                    }
                } else {
                    // Not a macro call → copy line
                    output.add(line);
                }
            }
            return output;
        }
    
}

Output

----- EXPANDED CODE -----
START 100
ADD AREG,A
SUB BREG,B
MOVER CREG,=2
SUB AREG,X
ADD BREG,Y
END