A pseudo-programming language made to overengineer a guessing game.

GuessingGame.java

/*
NUMBER GUESSING DOMAIN-SPECIFIC LANGUAGE IN JAVA
BY LUKE I. WILSON
 */

package org.vv;

import java.util.ArrayList;
import java.util.Scanner;
import java.util.Random;

public class GuessingGame {

    public enum Token {
        GOTO, RET, SETRAND, READ, SAY, LBL, JL, JG, JE
    }

    public static class Instr {
        public Token t; // instruction
        public String op; // operand

        public Instr(Token t, String op) {
            this.t = t;
            this.op = op;
        }
    }

    // translate the instructions to a pseudo-abstract syntax tree of Instr
    public static ArrayList<Instr> lex(String[] lines) {
        ArrayList<Instr> instrs = new ArrayList<>();

        for (int i = 0; i < lines.length; i++) {
            String l = lines[i].strip().toLowerCase();
            if (l.isEmpty()) continue;
            else if (l.startsWith("goto")) {
                String r = l.substring(5);
                instrs.add(new Instr(Token.GOTO, r));
            }
            else if (l.startsWith("ret")) instrs.add(new Instr(Token.RET, null));
            else if (l.startsWith("setrand")) instrs.add(new Instr(Token.SETRAND, null));
            else if (l.startsWith("read")) instrs.add(new Instr(Token.READ, null));
            else if (l.startsWith("say")) {
                String r = l.substring(4);
                instrs.add(new Instr(Token.SAY, r));
            }
            else if (l.startsWith("lbl")) {
                String r = l.substring(4);
                instrs.add(new Instr(Token.LBL, r));
            }
            else if (l.startsWith("jl")) {
                String r = l.substring(3);
                instrs.add(new Instr(Token.JL, r));
            }
            else if (l.startsWith("jg")) {
                String r = l.substring(3);
                instrs.add(new Instr(Token.JG, r));
            }
            else if (l.startsWith("je")) {
                String r = l.substring(3);
                instrs.add(new Instr(Token.JE, r));
            }
        }

        return instrs;
    }

    public static void interpret(ArrayList<Instr> instrs) {
        Scanner scan = new Scanner(System.in);
        Random rando = new Random();

        int r = 0, x = 0, y = 0; // Program registers

        loop: for (int pc = 0; pc < instrs.size(); pc++) {
            Instr instr = instrs.get(pc);
            switch (instr.t) {
                case GOTO:
                    for (pc = 0; pc < instrs.size(); pc++) {
                        if (instrs.get(pc).t == Token.LBL && instrs.get(pc).op.equals(instr.op)) break;
                    }
                    break;
                case RET: break loop;
                case SETRAND: r = rando.nextInt(10) + 1; break;
                case READ: x = scan.nextInt(); break;
                case SAY: System.out.println(instr.op.toUpperCase()); break;
                case LBL: break;
                case JL: if (x >= r) break;
                    for (pc = 0; pc < instrs.size(); pc++) {
                        if (instrs.get(pc).t == Token.LBL && instrs.get(pc).op.equals(instr.op)) break;
                    }
                    break;
                case JG: if (x <= r) break;
                    for (pc = 0; pc < instrs.size(); pc++) {
                        if (instrs.get(pc).t == Token.LBL && instrs.get(pc).op.equals(instr.op)) break;
                    }
                    break;
                case JE: if (x != r) break;
                    for (pc = 0; pc < instrs.size(); pc++) {
                        if (instrs.get(pc).t == Token.LBL && instrs.get(pc).op.equals(instr.op)) break;
                    }
                    break;
                default:
                    throw new IllegalStateException("Unexpected value: " + instr.t);
            }
        }
    }

    public static void main(String[] args) {
        // Only three available registers: r, x, and y
        String[] dsl_prog = new String[]{
                "    SETRAND", // rand -> r
                "    SAY Guess my number.", // print
                "LBL loop",
                "    READ", // read value to x
                "    JE eq", // jump to eq if value at x is equal to r
                "    JL l", // jump to l if value at x is less than r
                "    JG g", // jump to g if value at x is greater than r
                "LBL l",
                "    SAY Number too small!",
                "    GOTO loop",
                "LBL g",
                "    SAY Number too big!",
                "    GOTO loop",
                "LBL eq", // the jump label for equal
                "    SAY Goodbye!",
                "    RET" // exit program
        };
        ArrayList<Instr> dsl_ast = lex(dsl_prog);
        interpret(dsl_ast);
    }

}