--- Input ---
"(a 13)(defun a(b) (let ((c 8)) (write (* 2 (+ c b)))))"

--- Tokens ---
0: (
1: string='a'
2: int=13
3: )
4: (
5: defun
6: string='a'
7: (
8: string='b'
9: )
10: (
11: let
12: (
13: (
14: string='c'
15: int=8
16: )
17: )
18: (
19: write
20: (
21: *
22: int=2
23: (
24: +
25: string='c'
26: string='b'
27: )
28: )
29: )
30: )
31: )

--- Expressions ---
Expression: pos=(0,32); depth=1
        VAR; name=a
Expression: pos=(2,32); depth=2
        Int_Lit; value=13
Expression: pos=(3,32); depth=2
Expression: pos=(4,32); depth=1
        Defun
Expression: pos=(10,32); depth=3
        Let
Expression: pos=(13,32); depth=4
        VAR; name=c
Expression: pos=(15,32); depth=5
        Int_Lit; value=8
Expression: pos=(16,32); depth=5
Expression: pos=(17,32); depth=4
Expression: pos=(18,32); depth=3
        Write
Expression: pos=(20,32); depth=4
        [+,-,*,/]
Expression: pos=(22,32); depth=5
        Int_Lit; value=2
Expression: pos=(23,32); depth=5
        [+,-,*,/]
Expression: pos=(25,32); depth=6
        VAR; value=c
Expression: pos=(26,32); depth=6
        VAR; value=b
Expression: pos=(27,32); depth=6
Expression: pos=(28,32); depth=5
Expression: pos=(29,32); depth=4

--- Tree ---
[expressions
  [let_fun_var 'a'
    [13]]
  [return]
  [defun 'a'
    [bind_vars
      [bind_var 'b']]
    [expressions
      [let
        [let_fun_var 'c'
          [8]]
        [write
          [*
            [2]
            [+
              [c]
              [b]]]]]]]]

--- Evaluate ---
42