--- Input ---
"(let ((x (+ 19 6)) (y 11)) (write (- x y)))"

--- Tokens ---
0: '('
1: 'let'
2: '('
3: '('
4: 'x'
5: '('
6: '+'
7: '19'
8: '6'
9: ')'
10: ')'
11: '('
12: 'y'
13: '11'
14: ')'
15: ')'
16: '('
17: 'write'
18: '('
19: '-'
20: 'x'
21: 'y'
22: ')'
23: ')'
24: ')'

--- Expressions ---
Expression: pos=(0,25); depth=0
        Let
Expression: pos=(3,25); depth=1
        Str_Lit; value=x
Expression: pos=(5,25); depth=2
        [+,-,*,/]
Expression: pos=(7,25); depth=3
        Int_Lit; value=19
Expression: pos=(8,25); depth=3
        Int_Lit; value=6
Expression: pos=(9,25); depth=3
Expression: pos=(10,25); depth=2
Expression: pos=(11,25); depth=1
        Str_Lit; value=y
Expression: pos=(13,25); depth=2
        Int_Lit; value=11
Expression: pos=(14,25); depth=2
Expression: pos=(15,25); depth=1
Expression: pos=(16,25); depth=0
        Write
Expression: pos=(18,25); depth=1
        [+,-,*,/]
Expression: pos=(20,25); depth=2
        Str_Lit; value=x
Expression: pos=(21,25); depth=2
        Str_Lit; value=y
Expression: pos=(22,25); depth=2
Expression: pos=(23,25); depth=1

--- Tree ---
[let
  [let_dec 'x'
    [+
      [19]
      [6]]]
  [let_dec 'y'
    [11]]
  [write
    [-
      [x]
      [y]]]]

--- Evaluate ---
14