eval 1+2*3+(4+5);

eval 1+2*3+(4+5);

 1    root
 2     |
 3    prog
 4     |
 5     +
 6  ___|___
 7  |     |
 8  +     +
 9 _|__  _|__
10 |  |  |  |
11 1  *  4  5
12   _|__
13   |  |
14   2  3
15 ret: 6, n1: 2, n2: 3
16 ===========================
17    root
18     |
19    prog
20     |
21     +
22  ___|___
23  |     |
24  +     +
25 _|__  _|__
26 |  |  |  |
27 1  6  4  5
28 ---------------------------
29 ret: 7, n1: 1, n2: 6
30 ===========================
31 root
32  |
33 prog
34  |
35  +
36 _|__
37 |  |
38 7  +
39   _|__
40   |  |
41   4  5
42 ---------------------------
43 ret: 9, n1: 4, n2: 5
44 ===========================
45 root
46  |
47 prog
48  |
49  +
50 _|__
51 |  |
52 7  9
53 ---------------------------
54 ret: 16, n1: 7, n2: 9
55 ===========================
56 root
57  |
58 prog
59  |
60  16
61 ---------------------------
62 ===========================
63 root
64  |
65 prog
66  |
67  16
68 ---------------------------