Added methods and this keyword

.eslintrc.js

@@ -11,7 +11,7 @@ module.exports = {
     },
     "parserOptions": {
         "ecmaVersion": 2018,
-        "sourceType": "commonjs"
+        "sourceType": "module"
     },
     "rules": {
         "no-console": 0

cli.js

@@ -79,7 +79,7 @@ const processOptions = args =>
     .map(arg => {
       const match = optionRegex.exec(arg)
       if (match) {
-        const [_, option, value] = match
+        const [, option, value] = match
         if (!value) {
           options[option] = !options[option]
         } else {
@@ -105,4 +105,4 @@ const main = argv => {
   }
 }
 
-return main(process.argv)
+main(process.argv)

errors.js

@@ -12,6 +12,16 @@ class LoxError {
   }
 }
 
+class RuntimeError extends LoxError {
+  constructor(msg, token) {
+    super(
+      `${nullable(token.lexeme && `at "${token.lexeme}": `)}${msg}`,
+      token.startCoordinates,
+      token.endCoordinates
+    )
+  }
+}
+
 class ReturnError {
   constructor(val) {
     this.value = val
@@ -33,12 +43,7 @@ const parseError = (msg, token) => {
   }
 }
 
-const runtimeError = (msg, token) =>
-  new LoxError(
-    `${nullable(token.lexeme && `at "${token.lexeme}": `)}${msg}`,
-    token.startCoordinates,
-    token.endCoordinates
-  )
+const runtimeError = (msg, token) => new RuntimeError(msg, token)
 
 const formatLoxError = (e, code) => {
   if (e instanceof LoxError) {
@@ -55,8 +60,9 @@ const formatLoxError = (e, code) => {
     const postErrorSection = code.substring(e.endCoordinates.index, postErrorStart)
 
     // Print Critical Code
+    const errorType = e instanceof RuntimeError ? 'Runtime Error' : 'Parse Error'
     return {
-      oneLiner: `Parse Error: ${e.toString()} at ${e.endCoordinates.line}:${e.endCoordinates.col +
+      oneLiner: `${errorType}: ${e.toString()} at ${e.endCoordinates.line}:${e.endCoordinates.col +
         1}`,
       preErrorSection,
       errorSection,

examples/classExample.lox

@@ -2,6 +2,8 @@
 class Lox {
   breakfast() {
     print "Toast";
+    this.hello = "toast";
+    return this.hello;
   }
 }
 
@@ -16,6 +18,7 @@ var loxInstance = Lox();
 
 loxInstance.category = "Breakfast";
 print loxInstance.category;
+print loxInstance.breakfast();
 
 print Lox();
 

examples/linkedList.lox

@@ -0,0 +1,42 @@
+// Linked List via Classes
+class Link {}
+
+fun newLink (value, next) {
+  var link = Link();
+  link.value = value;
+  link.next = next;
+  link.append
+  return link;
+}
+
+var ll = newLink(1, newLink(2, newLink(3, nil)));
+
+fun traverse(n, fn) {
+  fn(n);
+  if (n.next != nil) {
+    return traverse(n.next, fn);
+  }
+  return n;
+}
+
+fun printList(list) {
+  fun printNode (n) {
+    print n.value;
+  }
+  traverse(list, printNode);
+}
+
+fun append(list, newNode) {
+  fun walk (n) {}
+  var end = traverse(list, walk);
+  end.next = newNode;
+  return end;
+}
+
+print "list:";
+printList(ll);
+
+append(ll, newLink(40, nil));
+
+print "list:";
+printList(ll);

interpreter.js

@@ -9,6 +9,7 @@ const {
   Get,
   Set,
   Var,
+  This,
   Grouping,
   Return,
   While,
@@ -57,15 +58,22 @@ class LoxCallable {
     return null
   }
 
+  bind(instance) {
+    const env = new Environment(this.closure)
+    env.set({ lexeme: 'this' }, instance)
+    return new LoxCallable(this.declaration, env)
+  }
+
   toString() {
     return `<${this.declaration.name.lexeme}()>`
   }
 }
 
 class LoxClass extends LoxCallable {
-  constructor(name) {
+  constructor(name, methods) {
     super()
     this.name = name
+    this.methods = methods
   }
 
   call() {
@@ -85,11 +93,11 @@ class LoxInstance {
 
   get(token) {
     const name = token.lexeme
-    if (this.fields.has(name)) {
-      return this.fields.get(name)
-    }
+    if (this.fields.has(name)) return this.fields.get(name)
 
-    throw runtimeError(`Undefined property ${name}`, token)
+    if (this.klass.methods.has(name)) return this.klass.methods.get(name).bind(this)
+
+    throw runtimeError(`Undefined property "${name}"`, token)
     // return null
   }
 
@@ -126,6 +134,7 @@ class Interpreter {
     else if (expr instanceof Class) return this.visitClass(expr)
     else if (expr instanceof Get) return this.visitGet(expr)
     else if (expr instanceof Set) return this.visitSet(expr)
+    else if (expr instanceof This) return this.visitThis(expr)
     else if (expr instanceof Logical) return this.visitLogical(expr)
     else if (expr instanceof Call) return this.visitCall(expr)
     else if (expr instanceof While) return this.visitWhile(expr)
@@ -200,7 +209,12 @@ class Interpreter {
   visitClass(stmt) {
     // We set the name before initializing it so classes can self-reference
     this.environment.set(stmt.name, null)
-    const klass = new LoxClass(stmt.name.lexeme)
+    const methods = new Map()
+    for (let method of stmt.methods) {
+      const fun = new LoxCallable(method, this.environment)
+      methods.set(method.name.lexeme, fun)
+    }
+    const klass = new LoxClass(stmt.name.lexeme, methods)
     this.environment.assign(stmt.name, klass)
     return null
   }
@@ -225,6 +239,10 @@ class Interpreter {
     return object.set(expr.name, val)
   }
 
+  visitThis(expr) {
+    return this.environment.get({ name: expr.keyword })
+  }
+
   visitBlock(expr) {
     this.interpretBlock(expr.statements, new Environment(this.environment))
     return null

loxfmt.js

@@ -80,4 +80,4 @@ const main = argv => {
   }
 }
 
-return main(process.argv)
+main(process.argv)

parser.js

@@ -9,6 +9,7 @@ const {
   Class,
   Get,
   Set,
+  This,
   Grouping,
   Return,
   LoxFunction,
@@ -262,6 +263,7 @@ class Parser {
   call() {
     let expr = this.primary()
     while (true) {
+      //eslint-disable-line
       if (this.match(token.LEFT_PAREN)) {
         expr = this.finishCall(expr)
       } else if (this.match(token.DOT)) {
@@ -291,6 +293,7 @@ class Parser {
     if (this.match(token.TRUE)) return new Literal(true)
     if (this.match(token.NIL)) return new Literal(null)
     if (this.match(token.NUMBER, token.STRING)) return new Literal(this.previous().literal)
+    if (this.match(token.THIS)) return new This(this.previous())
     if (this.match(token.IDENTIFIER)) return new Var(this.previous())
 
     if (this.match(token.LEFT_PAREN)) {

types.js

@@ -109,6 +109,12 @@ class Return {
   }
 }
 
+class This {
+  constructor(keyword) {
+    this.keyword = keyword
+  }
+}
+
 class Class {
   constructor(name, methods) {
     this.name = name
@@ -137,6 +143,7 @@ module.exports = {
   Literal,
   Return,
   Logical,
+  This,
   LoxFunction,
   Grouping,
   Condition,