Interpreter

Building A Tree-walking Interpreter. It tokenized and parse source code into a REPL, building up an internal representation of code (abstract syntax tree), then evaluate this tree.

Major Parts;

• lexer
• parser
• Abstract Synatx Tree
• internal object system
• evaluator

Guided by "Writing An Interpreter in Go" by Thorsten Ball

Features

Variable Bindings

Using a keyword let to bind values, functions to name

let name = 1;
let add = fn(a, b) { return a + b; };

Functions

Functions are first-class, and support higher order functions.

Explicit return

fn(f, x) {
  return f + x;
}

Implicit return

let add = fn(a ,b) { a + b; };

calling function

add(1, 2);

Higher order function

let twice = fn(f, x) {
  return f(f(x));
}
let addTwo = fn(x) {
  return x + 2;
}
twice(addTwo, 2);

Arithmetic Expressions

let result = 10 * (20 / 2);

Data Structures

Array

let array = [1, 2, 3];

array[0] // -> 1

String

let name = "Go";

Hash Table

let map = {"key": "stringVal", "keyInt": 3};