JLox Interpreter Implementation

Following A book by Robert Nystrom Crafting Interpreters

Language Features

• Statements

  • Simple statements

    print "Hello, World!";
    

  • Block statements

  {
     print "Some statement";
     print "Some Second statement"; 
  }
  

• Variables

  var variable = "Some String";
  var pi = 3.14;
  var someValue = 25;
  
  print pi; // 3.14
  

• Control flow

      // if statement
      if (some_condition) {
          // Do stuff...
      } else {
          // Do alternate Stuff...
      }
      
      // while statement
      var i = 0;
      while (i < 20) {
          print i * i;
          i = i + 1;
      }
      
      // for loop statement
      for (var i = 0; i < 20; i = i + 1) {
          print i * i;
      }
      
      ...
  

• Functions

  fun someFunction(parameters) {
      // Do stuff...
  }
  someFunction();
  
  /**
  *   Some two numbers
  */
  fun sum(a, b) {
      return a + b;
  }
  
  print sum(2, 3); // 5
  

• Closures

  /**
  * Lets have our selft some closures
  */
  fun makeCounter() {
      var count = 0;
      
      fun counter() {
          print count;
          count = count + 1;
      }
      
      return counter;
  }
  
  var counter = makeCounter();
  counter(); // 0
  counter(); // 1
  

• Classes

  class SayHello {
      init(name) {
          this.name = name;
      }
      hello() {
          print "Hello, " + this.name + ".";
      }
  }
  
  var hello = SayHello("Patco");
  hello.hello() // "Patco"
  
  

• Inheritance

  class Person {
      init(firstName, lastName) {
          this.firstName = firstName;
          this.lastName = lastName;
      }
      
      info() {
          return this.firstName + " " + this.lastName;
      }
  }
  
  class Student < Person { // Ugh... This is the worst example yet...
      init(firstName, lastName, studentId) {
          super.init(firstName, lastName);
          this.studentId = studentId;
      }
      
      info() {
          return super.info() + ", " + this.studentId;
      }
  }
  
  var student = Student("Patco", "Ke...", 20220302);
  print student.info();
  

Installation

    # I suppose clone and compile with mvn
    λ mvn package --quiet
    λ java -jar target/jlox-0.01.jar [source]

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