中文 README

introduce

This repository was created because I wanted to learn C++. After finishing reading two book <C++ Primer> and <CMake Cookbook>, I needed to find a project to learn by doing.

It’s been a dream of mine since college to implement a programming language all by myself, even if it’s just a toy.

meanwhile, I was reading the book : Thorsten Ball <Writing a Interpreter in Go>.

A bold idea came to me: why don’t I rewrite the Interpreter’s Golang code of this book in C++ ? so I can learn C++ , and at the same time implement a simple Interpreter from scratch .

it took me about 24 days to complete the C++ code implementation, which replicates all the functionality of the Golang code.

Environment Requirements

• CMake 3.5 or later
• C++ 20

Language features

There are no dependencies on third-party libraries other than Catch2(catch.hpp) for unit testing.

• C-like syntax
• variable bindings
• integers and booleans
• arithmetic expressions
• built-in functions
• first-class and higher-order functions
• closures
• a string data structure
• an array data structure
• a hash data structure

let age = 1;
let name = "Monkey";
let result = 10 * (20 / 2);

let myArray = [1, 2, 3, 4, 5];
let thorsten = {"name": "Thorsten", "age": 28};

myArray[0] // => 1
thorsten["name"] // => "Thorsten"

let add = fn(a, b) { return a + b; };
let add = fn(a, b) { a + b; };
add(1, 2);

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


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

let addTwo = fn(x) {
  return x + 2;
};
twice(addTwo, 2); // => 6


let map = fn(arr, f) {
  let iter = fn(arr, accumulated) { 
    if (len(arr) == 0) {
      accumulated
    } else {
      iter(rest(arr), push(accumulated, f(first(arr))));
    } 
  };
  iter(arr, []);
};

let a = [1, 2, 3, 4];
let double = fn(x) { x * 2 }; 
map(a, double);

build , test, repl

build

➜  mkdir build
➜  cd build
➜  cmake ..
➜  cmake --build .

run test cases : ctest or ctest -V

➜ ctest
Test project /Users/path/to/project/build

    Start 1: test_lexer
1/5 Test #1: test_lexer .......................   Passed    0.01 sec
    Start 2: test_ast
2/5 Test #2: test_ast .........................   Passed    0.02 sec
    Start 3: test_object
3/5 Test #3: test_object ......................   Passed    0.01 sec
    Start 4: test_parser
4/5 Test #4: test_parser ......................   Passed    0.03 sec
    Start 5: test_evaluator
5/5 Test #5: test_evaluator ...................   Passed    0.03 sec

run repl : ./bin/mirror

➜  ./bin/mirror
Hello! This is the Mirror-Monkey programming language!
Feel free to type in commands


	########################
	#╭━━╮╱╱╱╱╱╱╱╱╭╮        #
	#╰┃┃╋━━┳┳╮╭━━╋╋┳┳┳┳━┳┳╮#
	#╭┃┃┫┃┃┃┃┃┃┃┃┃┃╭┫╭┫╋┃╭╯#
	#╰━━┻┻┻╋╮┃╰┻┻┻┻╯╰╯╰━┻╯ #
	#╱╱╱╱╱╱╰━╯             #
	########################

>> let add = fn(a, b) { return a + b; };
let add = fn(a, b) return (a + b);;
>> add(1, 2);
add(1, 2)
3