1==================
 2Identifiers
 3==================
 4
 5abc12
 6
 7---
 8
 9(source (identifier))
10
11==================
12Negation
13==================
14
15!abc
16
17---
18
19(source (not (identifier)))
20
21==================
22And/Or
23==================
24
25a || b && c && d
26
27---
28
29(source
30  (or
31    (identifier)
32    (and
33      (and (identifier) (identifier))
34      (identifier))))
35
36==================
37Expressions
38==================
39
40a && (b == c || d != e)
41
42---
43
44(source
45  (and
46    (identifier)
47    (parenthesized (or
48      (equal (identifier) (identifier))
49      (not_equal (identifier) (identifier))))))