• Overview

  • This project is a simple compiler

• Project Structure

  • src/main/java/com/classhole/compiler/lexer — the tokenizer/lexer
  • src/main/java/com/classhole/compiler/parser — has the parser
  • src/main/java/com/classhole/compiler/typechecker — has the type checking
  • src/main/java/com/classhole/compiler/codegenerator — for code generation
  • src/test/java — all the JUnit tests

• Build & Test Commands

  • mvn clean compile
    • Compiles all source files in src/main/java.
  • mvn test
    • Runs all tests under src/test/java.
  • mvn exec:java -Dexec.mainClass="com.classhole.compiler.Main"
    • Edit the code string in Main.java to any valid classhole program and run this to compile and print the generated JavaScript

Concrete Syntax var is a variable classname is the name of a class methodname is the name of a method str is a string i is an integer

type ::= Int | Boolean | Void | Built-in types classname class type; includes Object and String

comma_exp ::= [exp (, exp)*]

primary_exp ::= var | str | i | Variables, strings, and integers are
expressions ( exp ) | Parenthesized expressions this | Refers to my instance true | false | Booleans println ( exp ) | Prints something to the terminal new classname ( comma_exp ) Creates a new object

call_exp ::= primary_exp (. methodname ( comma_exp ))*

mult_exp ::= call_exp ((* | /) call_exp)*

add_exp ::= mult_exp ((+ | -) mult_exp)*

exp ::= add_exp

vardec ::= type var

stmt ::= vardec ; | Variable declaration var = exp ; | Assignment while ( exp ) stmt | while loops break ; | break return [exp] ; | return, possibly void if with optional else if ( exp ) stmt [else stmt] | { stmt* } Block

comma_vardec ::= [vardec (, vardec)*]

methoddef ::= method methodname ( comma_vardec ) type { stmt* }

constructor ::= init ( comma_vardec ) { [super ( comma_exp ) ; ] stmt* } classdef ::= class classname [extends classname] { (vardec ;)* constructor methoddef* }

program ::= classdef* stmt+ stmt+ is the entry point

Example (animals with a speak method):

class Animal { init() {} method speak() Void { return println(0); } } class Cat extends Animal { init() { super(); } method speak() Void { return println(1); } } class Dog extends Animal { init() { super(); } method speak() Void { return println(2); } }

Animal cat; Animal dog; cat = new Cat(); dog = new Dog(); cat.speak(); dog.speak();