Rust implementation of the famous Monkey programming language.

Monkey; The programming language that lives in books

This is a Rust implementation of the original book Writing An Interpreter In Go, which (as you've might have guessed) is written in Go. At the moment this is a Work In Progress. The current implementation has:

• Integers, Booleans, Strings, Arrays, HashMaps
• A REPL
• Arithmetic expressions
• Let statements
• First-class and higher-order functions
• (A few) Built-in functions
• Recursion
• Closures

Running Monkey:

You can start the REPL by:

$ cargo run --release -p interpreter

Or run a Monkey program by:

$ cargo run --release -p interpreter <some-program.mnl>

Excerpt of the Monkey Language

let fibonacci = fn(x) {
  if (x == 0) {
    0
  } else {
    if (x == 1) {
      return 1;
    } else {
      fibonacci(x - 1) + fibonacci(x - 2);
    }
  }
};

My own flavor

I took the liberty to change some behavior of the language.

• I don't like puts so we use print

>> print("foo" + "bar")
"foobar"

• added a insert method for mutable hashes and arrays.

>> let map = {1: "one"};    
>> map.insert(2, "two")
>> map
{1: "one", 2: "two"}