What's an interpreter, anyways?

int fib(int n) {
  if (n < 2) {
    return n;
  }
  
  return fib(n - 1) + fib(n - 2);
}

LISP by example

(+ 7 8) // 15
(list 1 2 3) // [1, 2, 3]
(cons 42 (list 1 2 3)) // [42, 1, 2, 3]
(car (list 1 2 3)) // 1
(cdr (list 1 2 3)) // [2, 3] 

+ variables, functions, ...

Lexing

(+ 10 (car (list 32 33 34)))
  => [
        "(", "+", "10", "(",
        "car", "(", "list", "1",
        "2", "3", ")", ")", ")"
     ]

Parsing

Interpreting